THE BIONOMICS OF DIOPSIS (DIPTERAL DIGPSIDAE) MD Off EPIIiACHKA S I K H S (COLEOPTEBA, COCGn'IELLIDAE) OH ORYZA SATI7A L . If? THE ACCHA PLAfflS A Thesis Presented to the Faculty o f A griculture University o f Ghana hy John ffrank Abu Department o f Orop Science, University o f Ghana, Legon, Ghana, June 1972. In the Requirements f o r the Degree Master o f Science (Crop Science) University of Ghana http://ugspace.ug.edu.gh £ 1 7 1 9 ^ 9 0 University of Ghana http://ugspace.ug.edu.gh i i DECLARATION I hereby declare that, except for references to other people's work which have been duly cited, this work is the result o f my own original research and that this thesis has neither in whole nor in part been presented for another degree elsewhere. (supervisor) Date; . .7 \ l j . University of Ghana http://ugspace.ug.edu.gh A B S T R A C T The b iology o f S iopsis species (D iptera; Diopsidae) and Epilachna s im ilis (Coleoptera; C occinellidae) was studied on the Acora P la in s . Of the three species o f Diopais found, D. thoracica caused the most severe damage to r ic e . AH the developmental stages o f these in sects are described and keys are provided fo r iden tify in g a l l the various stages o f the Diopsis species. D. thoracica exh ibits sexual dimorphism with regard to the in ter o rb ita l d istance. A high stalk in fe s ta t io n o f forty -e igh t per cent was recorded in the major rainy season. The para­ s ite s and altenate hosts o f these in sect species are discussed. A r t i f i ­ c ia l in festa tion o f r ic e stalks with the larvae o f D. thoracica demons­ trated that a single larva, could destroy 3 - 6 stalks during i t s l i f e time leading to a loss o f about nine percent in y ie ld . A ll the developmental stages o f B. s im ilis are described and a key provided fo r iden tify in g the four la rva l in sta rs . P ossib le con tro l measures against the Diopsis species and Epilachna s im ilis are discussed. i i iUniversity of Ghana http://ugspace.ug.edu.gh ACKNOWLEDGMENT I am deeply indebted to Mr. H.G. Morgan, my immediate supervisor, fo r his guidance, encouragement, cr it ic ism s and correction o f the manuscript. Special thanks are due to P rof. J.W. Tanner o f the Department o f Crop Science, Legon, Dr. G. S ch eibe lre iter o f the Commonwealth In stitu te o f B io log ica l Control, Kumasi and Dr. R. Kumar o f the Department o f Zoology, Legon, a l l o f whom served on the super­ v isory committee fo r th eir keen in te re s t, suggestions and help on eveiy aspect o f the work. I am gratefu l to the entire s t a f f o f the A gricultural Research Station, Kpong, p articu la rly Mr. E.J.A. Khan, Senior Research O ffice r , fo r providing r ice p lo ts and assistance on the f ie ld . Thanks are due to the s ta f f o f the Chinese R ice Farm, Dawhenya fo r the same reasons. I wish to express my gratitude to the U niversity o f Ghana fo r providing fin an cia l assistance. F inally thanks go to Mr. J.T. Quaynor fo r typing the manuscript. University of Ghana http://ugspace.ug.edu.gh VCONTENTS PAGE TITLE PAGE ' 1 DECLARATION i i ABSTRACT i i i ACKHOWLEDGMMT LIST OF TABLES v ii LIST OF FIGURES AND PLATES ** LIST OF APPENDICES x ABBREVIATIONS AND SSMBOLS xi 1 INTRODUCTION 1 2 REVIEW OF LITERATURE 3 2.1 Dip-psis spp 3 2.2 Epilachna similis 4 3 AREA OF INVESTIGATION 6 4 BIOLOGY OF THE PESTS 10 4.1 Materials end Methods 10 4.2 Biology o f Diopsis spp 14 4.2.1 Life Cycles 14 4 .2 .2 Description of the Immature Stages 18 4*2.3 Description o f the Adults 28 4 .2 .4 Keys fox the Identification of the Stages 32 4-2.5 Opposition Habits 34 4-3 Biology of Epilachna similis 36 4.3*1 Life Cycle 36 4 .3 .2 Description of the Immature Stages 37 4.3 .3 Key for the Identification of Larval Instars 45 4.3*4 Description of the Adults ' 45 4 .3 .5 Oviposition Habits 46 4.4 Discussion 47 5 SEASONAL POPULATION CHANGES 51 5.1 Materials and Methods 54' University of Ghana http://ugspace.ug.edu.gh v i PAGE ;? 5 .2 S eason a lity o f D iopsis spp 53 5 .3 S eason a lity o f Jj. s im ilis 70 5 .4 D iscussion 73 6 PAMSITIES JND jiLTENATE HOSTS 76 6.1 P arasites 76 6 .2 A lienate Hosts 79 7 . SXPEKCMMTS YCCES BIOPSIS THOBAGICJ. AKD SPILACHNA SIMILIS. 83 . 7 .1 . Damage Caused by D. th o ra c ic a and i t s E ffe c ts on the Y ie ld of R ice 83 7 .1 .1 M aterials and Methods • 83" 7 .1 .2 Observations and R esu lts 86 7 .1 .3 D iscussion 90 7 .2 . Food P reference and S u rv iva l T esta ?vith the Larvae o f E . s im ilis 90 7 .2 .1 ' Food P reference T est 91 ■ 7 .2 .2 S urvival T est 93 7 .2 .3 Dis emission % . 8 CONCLUSION 96 9 LITEEumJBE CITED 99 10 JPPENDIX 102 University of Ghana http://ugspace.ug.edu.gh v ii LIST OF TABLES TABLE PAGE 1 Duration o f Immature Stages o f Diopsis spp 17 2 Summary o f the duration o f the Immature Stages o f Epilachna s i m i l i s ............................. 37 3 Diopsis In festa tion on Bice at Kpong, March- , June 1971 . . . . . . ............................................ 54 4 Diopsis In festation on Rice at Kpong, July- September 1971 .......................................................... 55 5 Diopsis In festation on Rice at Kpong, l o v . - 1971 - February 1.972 .............................................. 56 6 Diopsis In festation on Rice at Dawhenya, A pril-Ju ly 1971 ........................................................ 57 7 Diopsis In festation on lice.; ’ateDawhenya, July-0ctober 1971 . . . . . ............................... 58 8 Diopsis In festation on Rice at Dawhenya, December 1971-April 1972 ..................................... 59 9 Adult Diopsis C ollected by Net Sweeping at Kpong, March-June, 1971 . . ............................. , 66 10 Adult Diopsis C ollected by Net Sweeping at Kpong, July-September, 1971 ............................. 66 11 Adult Diopsis Collected by Met Sweeping at Kpong, November 1971-February 1972 ................. 67 12 Adult Diopsis C ollected by l e t Sweeoine at Dawhenya, A pril-Ju ly 1971 . . . . . . . . . 67 13 Adult Diopsis C ollected by Net Sweeniner at Dawhenya, July-October, 1971 ............................. 68 14 Adult Diopsis C ollected by Net Sweeping at Dawhenya, December 1971-April 1972 ................. 68 15 Comparison o f "Whitehead" and Maximum In fes­ tation .............................................................. 69 16 Sex Ratios o f Diop si s s p p ................................. 69 17 E. s im ilis C ollection at Kpong. March-June. 1 9 7 1 ................................................... .................... 71 18 E. s ia d lis C ollection at Kpong. June-Sent.. 1 9 7 1 .............................................................................. 71 University of Ghana http://ugspace.ug.edu.gh T i l l TABLE ,19 E. sim ilis Collection at Kpong, November 1971 - February 1972 . . . . . . 20 A r t if ic ia l Infestation of Rice Stalks with Larvae of D. thoraoica . . . 21 Effect of Intensities and Age cf Infestation vdth Larvae of D. thoraoica on tillering of Rice . . . . . . 22 E ffect of Intensities and Age of Infestation with Larvae of D. thoraoica on Yield of Rice . . . . . . 23 Food Preference in the Larvae of snmlxg . . . . . . ' . . . PASS 72 87 •88 89 93 21*. Mean Duration of Larval Instars on S . s im ilis on fo u r M ajor Cereals o f Ghana 94 University of Ghana http://ugspace.ug.edu.gh LIST OF FIGURES AND PLJffiES FIGURE ‘ PAGE 1 The A ccra P la in s ........... 7 2 Immature stages of B. thoracica . . . . . . . . . 20 3 Immature stages of D. tenuipes . . . . . . . . . . 23 4 Immature stages of D» ichneumonea . . . . . . . 27 5 Abdominal Segment o f S . s im ilis showing the positions of the Scoli . . . . . . 40 6 Immature stages o f E . s im il is . . . . . . . . . . . 43 7 Diopsis Infestation at Kpong . . . . . ............... 60 8 Abundance of D. thoracica at Kpong * . . . . . 61 9 Abundance cf D» tenuipes at Kpong . . . . . . . 62 10 Diopsis Infestation at Dawhenya . . . . . . . . . 63 11 Abundance of D. thoracica at Dawhenya . . . 64 12 Abundance of D. tenuipes at Dawhenya . . . 65 PLOT 1 Adult Diopsis spp . . . . . . . . . . . . . . . . . . . . . . . 30 2 Epilachna s im ilis ................ 44 ix University of Ghana http://ugspace.ug.edu.gh XLIST OF APPENDICES iPPENDIX PAGE 1 M eteorological Data; Kpong 102 2 M eteorological Data; Dawhenya 103 3 Summary o f t - t e s t on Adult D. thoracica 104 4 Analysis o f Variance Table fo r Humber o f B ice T ille r s at M a tu r ity ........................ . 104 5 Analysis o f fariance Table fo r Grain H e ld o f E ice . . . . . ............................... 105 6 M eteorological Data; Greenhouse Experi­ ment ................................................................................. 105 University of Ghana http://ugspace.ug.edu.gh xi ABBREVIATIONS AID SYMBOLS cm centimeter cs cephalopharyngeal steele df degrees o f freedom Fig. Figure 00 degrees iCentigratfe m gram fars hours Inf. Infestation Max. Maximum Min. Minimum iirni millimeter MS Mean Square Ho. Number NS lion Significant HI Relative Humidity SD Standard Deviation SS Sum of Squares Temp Temperature * Significant at level m Significant at Xfo level Percent; Percentage. University of Ghana http://ugspace.ug.edu.gh 1. INTRODUCTION - E ice, Oryza sativa L. i s now firm ly established as one o f the staple foods in Ghana and i t s production has attracted national attention in recent years. Ghartey (1970) estimated that Ghana consumes about 90 m illion kilograms o f r i c e annually. Nearly h a lf o f this.amount i s imported at a cost o f approximately seven m illion ced is and i t i s assumed that the import b i l l w ill stand at eleven m illion cedis by 1975 i f r ic e production i s not stepped up. With th is in mind the Ministry o f Pood and A griculture has in te n s ifie d i t s e f fo r ts in pro­ viding f a c i l i t i e s fo r large sca le cu ltiv a tion o f both irr ig a te d and ra in -fed r ic e . The major areas o f cu ltiv a tion now include the Northern and Upper Regions, the Brong lhafo Region, the Western Region, the V olta ' Region and parts o f the Accra P lains. While the large sca le cu ltivation o f r ic e i s l ik e ly to save some foreign exchange, i t must not be forgotten that i f e f fe c t iv e control measures are not taken against pest problems the aims cannot be achieved. Insect pests constitu te one o f the p rin c ip a l causes o f low y ie ld s in the majqr r ic e growing areas o f the world. Roughly one hundred in sect species are known to in fe s t and, damage r ic e p lants throughout the world and larva l stem borers are among the most serious pests o f th is crop ( Anon, 1969, 1970; Akinsola, 1970). Most o f these larvae belong to the two in sect orders, Lepidoptera and Diptera. They bore into the r ic e stem shortly University of Ghana http://ugspace.ug.edu.gh a fte r hatching and fo r moat o f th e ir l i f e remain insida-the stem, feeding either k il l in g i t , o r so in ju rin g the plant that i t produces l i t t l e or no crop. The lepidopterous larva l borers which belong to the fam ilies Pyralidae and Noctuidae have been recorded as major pests o f r ic e in almost a l l the r ic e growing regions o f the world, including West A frica . Among the Diptera the genus Diopsis contains species which are borers o f r i c e and other graminaceous crops. In West A frica the damage caused by Diopsis species i s considered to be more serious than that caused by the lepidopterous borers (Lever, 1969; Anon, 1970). Recent reports by Van Halteren (1970), Simmonds (1970) and Schroder (1971) ind icate that Diopsis spp pose a threat to r ic e cu ltiv a tion in South-Eastern Ghana. However, n o i*o f them gave the degree o f in fes ta ­ tion . Quite recently attention has also been drawn by Breniere (1969) and Schroder (1970) to outbreaks o f the le a f feeding in sect Epilachna sim ilis Muls. on some r ic e fauns in the Eastern and Volta Regions. The importance in Ghana o f . D iopsis spp and E. s im ilis as pests o f r ic e i s not quite clea r. The present study aims at providing some o f the basic 0information on these in sects . University of Ghana http://ugspace.ug.edu.gh 22.' REVIEW OS' LITERATURE 2.1 Diopsis spp (Diptera; Diopsidae) The Diopsis spp are found m ainly.in A fr ica and Asia (Descamps, 195Tb). As p ecu liar looking stalked-eye f l i e s adult diopsids a ttracted the attention o f co lle c to rs as fa r "back as 1775» yet very l i t t l e was knoxnj about the genus u n til 1957 when Descamps (1957a; b) gave an account o f the b iology and morphology o f twenty species o f the fam ily Diopsidae in Northern Cameroun.’ Before then the lite ra tu re contained only scanty observations on the behaviour o f the adults o f a few species with p ra ctica lly no inform ation on the immature stages. Since very l i t t l e was known about the Diopsis spp u n til quite recently , i t i s not certain when they became pests o f r ic e and other graminaceous crops. Simmonds (1970) c ite d Mallay (1920) as having recorded Diopsis a p ica lls Dalm. in association with the maize sta lk borer Busseola fusca Fuller in South A frica . Compiling a l i s t o f in sect pests o f r ic e in Northern Cameroun Descamps (1956) recognised Diopsis thoraoica Westwood, Diopsis tenuipes Westwood, D iopsis c o l la r is Westwood, and Diopsis s e r v e i l le i Marquart as stem borers. Descamps ( 1957b) again recorded f if te e n diopsids on graminaceous plants in Northern Cameroun. Out o f th is number seven were said to be very serious pests and most o f them were on r ic e with a few on m ille t and University of Ghana http://ugspace.ug.edu.gh sorghum. The same work also reported the occurence o f a number o f Diopsis spp in the Congo, Natal,, East A fr ica , Senegal, Kenya, Zambezi, Rhodesia, Uganda, Mozambique, Guinea, Gabon and Somalia. Van Bruggen (1961) has recorded D. thoracica , D. tenuipeis, and D. a p iea lis in South A frica . Jerath (1965) and Akinsola (1970) observed D. thoracica and D. ap iea lis as pests o f r ic e in N igeria but the attack was said to be mild. Jordan (1966) and Morgan (1970) reported that severe damage is done to r ic e in S ierra Leone by Diopsis spp and Breniere (1966; 1969) made sim ilar observations in Madagascar, Dahomey, Ivory Coast and Upper Volta. In Shana^Van Halteren (1970) recorded D. thoracica and D. ap iea lis at the Kpong A gricultural Research Station add stated that the former i s the most serious o f a l l in sect pests encountered on r ic e . Shortly a fte r th is Schroder (1970) reported that 35-60fo o f r ic e h i l l s were damaged by Diopsis spp in the Volta Region. 2 .2 Epllachna s im ilis Muls. (Coleoptera; Coceinellidae) The members o f the fam ily fioccin e llid ae are the well-known lady­ bird beetles, the greater number o f which are carnivorous and predaceous, feeding during both the larva l and adult stages, on aphids, mealybugs and other in sects . A comparatively small group are phytophagous and they constitute the subfamily Efcilachninae to which the genus Epilac>m» belongs. Species o f th is genus have been recorded in many countries University of Ghana http://ugspace.ug.edu.gh as pests o f cucurbits, beans, cotton and several other crops. A w e ll- known pest under th is genus i s the Mexican bean beetle Epilachna varivestis Muls. o f North America. The lite ra tu re on the genus as a whole and Epilachna s im ilis Muls. in p articu lar i s very scanty. Peacock (1914) observed that E. s im ilis fed on the leaves o f cotton in N igeria. This was confirmed by Jerath (1965) who l is te d the same species a sa n e o f the important pests o f r ic e and added other graminaceous crops to i t s host range. Smithers (1957) l is te d several species o f Epilachna feeding on various crops in Southern Ehodesia and mentioned E. s im ilis in p articu lar as a pest o f maize, oats, wheat, sorghum, barley and some pasture grasses. S im ilarly Wa1lker( 1958) recorded E. s im ilis on r ic e and maize in East A frica . Schmutterer (1969) found th is pest widely d istributed on various grami^ neae in East A frica , Ehodesia, South A frica and Sudan and Breniere (1969) made sim ilar observations in Senegal, Ivory Coast, Ghana and Dahomey. In Ghana the occurence o f 15. s im ilis on r ic e has been confirmed by Van Halteren (1970), but while he maintained that th is pest i s o f minor importance Schroder (1970) reported that the damage caused i s severe in the Eastern and V olta Regions o f the country. University of Ghana http://ugspace.ug.edu.gh 3 . THE AREA OP MVESTIGiTIOlt The work carried out in th is study was re s tr ic te d to the Accra Plains which i s located in the South-Eastern, com er o f Ghana between latitudes 6° 14' N and 5° 29' H and longitudes 0° 23' ¥ and ©° 41* E. The area i s approximately 3750 square kilom eters and roughly triangu­ la r in shape. I t i s bounded on the west by the ikwapim Range and the Wei ja H ills , on the north and east by the lower V olta R iver and on the south by the Gulf o f Guinea between the mouth o f the V olta and a poin t ten miles west o f Accra (F ig .1 ). The area has a gently slop ing topography. There are no permanent rivers and most o f the major streams flow fo r only a few months during and' a fte r the rainy seasons and dry out to pools in the main dry seasons. Mean annual ra in fa ll ranges from 75cm at the coast to 125cm in the extreme north and the greater p a r t .o f the p la in s receive le ss than 90cm with to ta ls varying considerably from year to year. There are two rainy seasons; March to July which records the highest rains and September to December which i s the minor season. Temperatures are highest during the main dry season from December to February and lowest during the short dry season which i s from July to August. Absolute minimum temperatures range between 13?C and 40°C ) but proximity to the sea and high a ltitu des such as the Akwapim Range reduces the temperature. Hiataidities are high throughout the year. The average monthly University of Ghana http://ugspace.ug.edu.gh SCALE FIG. I. ACCRA PLAINS WITH THE SPECIES RECORDED AT THE PLACES VISITED. KEY ■ D . TMORACICA K D. TENNIPES A E. SIMILIS E J D. 1CHNEUMONEA Q D SPECIES d University of Ghana http://ugspace.ug.edu.gh re la tiv e humidity are 60-75$ in the afternnon and 91-97$ at n ight. There are l i t t l e variations in daylengths. These seldom f a l l below or r is e above 1 ! hours 50 minutes and 12 hours 25 minutes respectively . The s o ils o f the Accra Plains f a l l into seven major groups, v i z . Shallow reeky s o i l s , Red earths, P a llid sands, Grey ,earths, Black clays, A llu v ia l clays, and Leeve and dune sands (Brammer, 1967)* A ll o f the present work ifas carried out on the Black clays. These are developed over basic gneisses and con sists o f dark grey to black, heavy clays about^?®—120cm deep . They are very stick y and p la s t ic when wet but become hard and compact bn drying when they also develop wide v e rtica l cracks. Their cu ltivation poses serious problems because o f the physical properties, f t i§ considered that with the aid o f irr ig a tion and heavy machineiy they could become highly productive with r ic e and sugarcane. The Black clays carry medium grassland vegetation with T etiveria fu lv ibarb is Trin, Stapf, as the major grass. In the south there is almost no woody vegetation, but scattered low shrubs appear as the Shai H ills are approached. Low stunted trees are frequent in the north. Forest and th ickets occur on some o f the basic gneiss inselbergs and along,the borders o f stream channels. A ll laboratory work waso conducted at Legon while most o f the fieldwork was „■ carried out at the U niversity o f Ghana A gricultural Hesearch Station at Kpong and the Chinese A gricultural Mission Farm at University of Ghana http://ugspace.ug.edu.gh Dawhenya with a few observations at Aehiaman and Asutsuare. These places were selected on the basis o f th e ir proximity to Legon and the a v a ila b ility o f r ic e f ie ld s . The Kpong station was established in 1954 to conduct investigations on the Black clays under ir r ig a t io n . The mean annual r a in fa ll i s about 118cm and the temperature ranges from 19°0 to 35°G. Water fo r ir r ig a ­ tion i s pumped through a pipe lin e from the V olta Hiver to a reservo ir on the station . The Dawhenya Farm was established in 1959 and has an annual rain­ f a l l o f about 75cm and mean monthly temperature ranging from 21 °C to 32°G. Water fo r irr ig a tio n i s supplied by an earth dam across the Dechidaw Siver. University of Ghana http://ugspace.ug.edu.gh 10 4. BIOLOGY OP THE PESTS 4.1 Materials and Methods 4.1.1 The Insects Studied A to ta l o f four in sect species were studied. These were D iopsis thoracica Westwood, D iopsis tenuipes Westwood, D iopsis ichneumonea Dahl, and Epilachna s im ilis lu ls . One other d iopsid was occasion a lly co lle cted from the f ie ld , but i t s immature stages could not be obtained. This species has not been id e n tifie d and i s re ferred to as D iopsis sp d. in the tex t. D iopsis tenuipes Westwood i s synonymous with Diopsis a p ica lis Dalm. (Breniere, 1969). The id e n tifica t io n o f a l l the in sect specimens was carried out at the B ritish Museum o f la tu ra l H istory. 4-1-2 The S ice V arieties Used Two r ic e v a r ie t ie s which were among the most widely grown in the country at the time o f tth is study were used. They are SSL Alupi and C4-63. SKI> Alupi, which i s a long-grain variety orig in atin g from Surinam was employed fo r a l l fieldwork at Kpong. I t has' a maturation period o f 150 days from sowing to harvesting, i s s lig h t ly photosensitive, o f medium t i l le r in g and grows to a maximum height o f about 135cm. 04-63 i s a medium-sized grain r ic s se lected from crosses at the University o f Ph ilipp ines. I t i s day neutral, t i l le r in g capacity i s University of Ghana http://ugspace.ug.edu.gh 11 moderately high, maximum height i s approximately 105cm, and has a maturity period o f about 125 days from sowing to harvesting. This variety was used fo r a l l fieldwork at Dawhenya, fo r feeding in sects in the laboratory and fo r host preference and s p e c if ic it y te s ts at Legon. 4-. 1.5 Methods fo r the study o f the B iology o f the Insects AH in sect specimens were reared in a laboratory in which the temperature range was 23 - 26° C (mean = 25°C) and the re la tiv e humidity range was 72 - 79?*> (mean = 75^). With the exception o f D. 'tenuipes i t was convenient to rear D iopsis eggs in p e tr i dishes o f 9cm diameter. / Each dish was provided with a moist f i l t e r paper bed on which several eggs o f the same species were put and the dish covered with i t s l id . The paper was subsequently moistened when necessary. Larval cannibalism was observed in D. tenulpes and the eggs were therefore, reared sin gly in 1 x 5cm glass v ia ls plugged with moist cotton wool. Eggs o f E. s im ilis were reared in the same way as those o f D. tenuipes. Several attempts to rear D iopsis larvae on cut r i c e stalks fa ile d . Only the o lder larvae which were ready to pupate survived. I t was therefore necessary to use potted r ic e p lants. Each larva was put on a potted r ice h i l l con sistin g o f f iv e to seven sta lks. The pot and i t s contents were enclosed in 45 x 45 x 7cm cage with 0 . 2mm wire mesh on a l l the sides except the bottom which was wooden. The plants were University of Ghana http://ugspace.ug.edu.gh watered when necessary. The larval instars o f D iopsis were, carefully- dissected out o f the stalks and examined each day. , Larvae o f E. s ig iilis were reared in 2 .5 x 7 . 5cm glass v ia ls . Frefih leaves o f .r ic e seedlings were provided everyday. All pupae were reared in 2.5 x 7 .Son vials plumed with moist cotton wool. Except where otherwise stated, potted r ic e seedlings covered with 10 x 15cm lantern glass globes were used as ov ip os ition cages. The adult Diopsis .species were fed on cotton wool soaked with d ilu te honey solu tion . The descriptions and measurements o f the various stages were based on both f ie ld -c o l le e te d and laboratory-reared specimens. A ll measure­ ments were made with a Becks binocular microscope f i t t e d with an ocular micrometer and are expressed in m illim eters. D efin ition s o f the measurements are as fo llo w s :- (a) Diopsis Length o f egg - to ta l length measured dorsally Width o f egg - to ta l width taken dorsa lly Length o f larva - to ta l length, dorsally Width o f larva - maximum width measured on the fourth abdominal segment. Length o f cephalopharyngeal skeleton - to ta l length from the base to the tip Length o f pupa - to ta l length, dorsa lly . 12 University of Ghana http://ugspace.ug.edu.gh Width o f pupa - maximum width taken on the fourth segment Length o f Adult - to ta l length, dorsally ' In te r -o rb ita l distance - to ta l d istance between the extreme borders o f the two eyes o f the , adult. (b) E. s im ilis Length o f egg - to ta l length from the base to the tip Width o f egg - maximum width measured at the base Width o f head capsule o f larva - maximum width taken between the antennae Length o f larva - 'tota l length, dorsa lly Width o f larva - maximum width taken on the th ird abdominal ‘ segnent Length o f pupa - to ta l length, dorsally Width o f pupa. - maximum width taken at the anterior end. With the( exception o f adult D iopsis a l l measurements were made on tea specimens in each case. The mean and the standard deviations were calculated. She measurements o f adult D iopsis "were made on f i f t y specimens. A ll i llu s tra tio n s were made with the aid o f a camera lucida . 13 University of Ghana http://ugspace.ug.edu.gh 4-2 B iology o f Diopsis spp 4.2.1 L ife Cycles (a) D. thoraciea The incubation period fo r the eggs i s 2-5 days with most o f the eggs hatching on the th ird day a fte r laying. The larvae emerged by making s l i t s along the egg shall qmite c lo se to the anterior knob. Most larvae entered the r ic e stalk within about th rity minutes, Usually moving down the in side o f the terminal le a f sheath. They bored down to the base o f the le a f to feed , cu tting o f f the le a f which withers within 2-4 days, depending on the age o f the r i c e . This symptom o f withered terminal le a f i s referred to as "deadheart". Sometimes the larvae fed above the primodia. In such cases the meristems were not k il le d , and although "deadheart" occured, the severed portions were displaced by new growth and the stalks survived. When the severed leaves began to decompose the larvae l e f t the o ld stalks to attack new ones, choosing fo r th e ir ex it the s l i t s between the sheaths and the terminal leaves. O ccasionally some larvae got squeezed in the s l i t s and died. The o ld larvae re-entered healthy stalks e ith er within the h i l l i t previously in fe s te d 'o r chose a completely new h i l l . Where la r v a l feeding in the r ic e sta lk occured a fte r pan icle in it ia ­ tion , the severing o f the growing parts resulted in the death o f the panicles; some o f them did not emerge at a l l , and those that had already- emerged did not produced grains. This condition o f empty pan icles i s 14 University of Ghana http://ugspace.ug.edu.gh referred to as "whitehead". There axe three larval inetars. The duration of these instars are given in table 1. In the laboratory the total larval l i fe was 2 5 - 3 3 days (mean = 29.days) during which 3 - 6 stalks (mean = 4-8 stalks) were destroyed by each larva. Mien reared on six weeks old rice the larvae were observed to change stalks after every 4-9 days, stalk changing being more frequent as the larvae got older. In most cases the mature larva se lected a healthy sta lk fo r pupa­ tion . In the f i e ld i t was quite rare to 'fin d a pupa in a- s ta lk with "deadheart" o r "whitehead". frequently pupae were found in h i l l s which showed no v is ib le sign o f attack, fh is suggests that the larva might have been carried to the new h i l l by flo a t in g in the Ir r ig a tio n water. In most cases pupation occured in the outermost sheath o f the sta lk at a height o f 3 - 8cm above s o i l le v e l. The larva rested with i t s anterior end Upwards and i t s ventral surface in the groove o f the sheath. I t then secreted a white foamy substance to plug the groove at the anterior end. This transformation required a few hours to complete. The shortest time observed in the laboratory was about three hours. The duration o f the pupa i s shown in table 1. At ee losion , s l i t s occured at the anterior end o f the f i r s t segment o f the pupa and along the lengths o f the p a ir o f la te ra l sw ellings on segments 1 - 3 . As the insect forced i t s way out the p la te was raised and broke e ith er wholly or p a r tia lly on the fourth segment. Where pupa© were,kept in glass 15 University of Ghana http://ugspace.ug.edu.gh v ia ls i t was noticed that the fresh ly emerged adults attempted to get out o f the v ia ls by squeezing themselves through the s l i t s between the cotton wool and the glass . (b ) D. tenuities The eggs o f D. tenuipes hatched within two days a fte r laying and the larvae entered the r ic e sta lk in the same way as D. th oracica . However, D. tenuipes continued to l iv e and completed i t s l i f e in the same staUc, feeding on the decaying m aterial. In the f i e l d very young larvae were found in o ld decayed sta lk s. When both healthy and "dead- heart" stalks were o ffe red to f i r s t in sta r larvae starved fo r 24 hours a fter emergence, i t was found that both sources o f food were acceptable and made no d ifferen ce in the to ta l duration o f larval and pupal l i f e . The larvae pupated in the same sta lk into which i t bored. The pupae were usually found at the top o f the sheath with th e ir anterior ends upwards. Adult emergence occured in the same way as described fo r D. thoracica. (c ) D. ichneumonea Only a few specimen o f J). ichneumonea were available fo r study. The eggs hatched on the third day and larva l behaviour was very sim ilar to that o f D. tenuipes. The larvae completed th e ir l i f e and pupated in the same sta lk . Freshly emerged larvae could not, however, survive when o ffered only "deadheart" sta lk s. Like the other two species D. ichneumonea has three larval instars . The mode o f adult emergence i s the same as observed in D. thoracica. University of Ghana http://ugspace.ug.edu.gh 17 Table 1 Summary of the Duration of the Immature stages o£ Diopsis spp stage D U R A T I O N (days) D. thoraoica D. tenuipes D. ichneumonea Egg 2.7 ±t> .$ (2 -3 ) 2.0 ± 0 .0 (2-2) 5 .0 + 0 .0 (5-5) Larva 29.0 + 1.4 (25-53) 9 .7 I 0 .7 (8-11) 13.6 ± 1.1 (11-16) 1st Instar 7.7 - 0.9 (6-9) 2.6. t 0 .2 (2-5) 5.1 t 0 .8 (2-4) 2nd " 10.5 t 0 .7 (9-12) 2.4 ± 0.3 (2-5) 5 .4 ± 0.5 (3-4) 3rd " 10.8 ± 0 .6 (10-12) 4 .7 ± 0.2 (4-5) 7.1 t 0 .6 (6-8) Pupa 11.0 ± 0 .8 (10-12) 7.5 1 0 .2 (7-8) 8 .9 ± 0 .4 (8-10) Egg - Adult 42.7 + 1.8 (37-48) 19.0 ± 1.1(17-21) -25.5 t 1.4 ( 22-29) + Mean ++ Standard deviation +++ R§nge University of Ghana http://ugspace.ug.edu.gh 4 .2 .2 Description o f the Immature Stages (a) D. thoracica ( i ) Eggs (F ig . 2 .a ) Length - 1.7& + 0.&3 (1 .65 - t . $8) Width - 0.42 ± 0.02 (0 .38 - 0.45) The eggs are cream white, hut occasion a lly some are ta inted black either p a r t ia lly or wholly. I t has a thick sh e ll which is ridged lengthwise. The middle i s s lig h t ly swollen and the ventral s ide which i s pressed to the support by a cementing gum i s fla tten ed . The two ends are raised and bear knobs. The anterior knob, p a r t ia lly separated from the rest o f the egg by a crescent, i s very f la t and i s about three times wider than long. The p osterior khob i s poin ted .- ( i i ) Larvae The larvae are generally white to cream and have a p a r t ia lly transparent skin. They are roughly cy lin d r ica l and con sists o f twelve segments the la s t o f which i s terminated by a forked t a i l . The two halves o f the t a i l contain a pair o f sp ira cles . The t a i l also bears short hairs at i t s extremity. The tracheal system i s o f the metapneu- s t i c form' in the f i r s t instar but becomes amphineustic in the second and third in stars . The p a ir o f prothoracic sp iracles are in the form o f f in g e r -lik e paddle. The mouthparts con sist o f a cephalopharyngeal + Mean, o f ten measurements . mm ) ++ Standard deviation o f mean +++ Range o f measurements. 18 University of Ghana http://ugspace.ug.edu.gh skeleton made up o f the follow ing three p artss- (1) a pair o f curved but sharp mandibular s c le r ite s ( 2) a hypostomal, s c r e lite ( 3) a pharyngeal s c le r i t e (term inology o f Imms, 1965) . F irst Instar (F ig.2 .B ) Width Length 2.61 - 0.31 (2 .45 - 3.25) 0.36 ± 0 .04 (0 .32 - 0.44) Length o f C.S. 0.21 ± 0.04 (0 .17 - 0.28) The f i r s t in sta r larva is whiter and more cy lin d rica l than the mature larva. The prothoracic sp iracles are absent, but the posterio sp iracles are seen.as a pa ir in the two halves o f the t a i l . The t a i l ends are rounded and bear very fin e hairs. Second In s ta r ' Length o f C.S. 0.82 ± 0.07 (0 .73 - 0.89) The second in star i s creamy white and more elorigated than the f i r s t in star. The tracheal system i s well, developed and c le a r ly seen through the skin.. Both the prothoracic and p oster ior sp iracles are present and are o f l ig h t brown colour. Third Instar (p ig .2. C) Length 11.81 ± 0.58 ( 10 .5 3 - 12 . 68) Width 1.63 ± 0.22 ( 1.2 1 - 1.87) Width Length 17.97 $ 0.33 (17.62 -1 8 .5 5 ) 3.02 ± 0.06 (2 .89 - 3.25) Length o f C.S. 1.18 ± 0.04 (1 .00 - 1.24) University of Ghana http://ugspace.ug.edu.gh & FR 3T INSTAR LARVA University of Ghana http://ugspace.ug.edu.gh University of Ghana http://ugspace.ug.edu.gh I t i s very sim ilar to the second in star in general appearance, but the ceplialopharyngeal skeleton and. the sp iracles are deeply p ig ­ mented, assuming a deep brown colouration . The larva i s pointed at both ends. The t a i l i s elongated, thick at the base and has a sharp apex. The ring o f hairs radiating from the end o f each h a lf o f the t a i l axe th icker .than those o f the f i r s t and second instars.■0 ( i i i ) Pupae ( f i g .2 . D; E) Length 10.81 ± 0.08 (10.69 - 10.90) Width 2.71 - 0.02 (2 .68 - 2.75) The pupae are o f the exarate type. They may have a triangular or fla tten ed appearance depending.on the shape o f the r ic e sheath in which pupation takes p lace. I t has a brownish red colour dorsa lly with a cream ventral surface. The anterior end slopes dorsa lly and tapers to give a very small f i r s t segment. There are a to ta l o f twelve segments. The anterior spiraeula? tubercules appear as a p a ir o f short knobs situated on the ventral surface o f the f i r s t segment. The spira­ cles are deformed and appear as a rin g o f n ipples at the end o f the knobs. In some specimen the knobs are fa lle n o f f and scars are noticed in th eir p osition s . Two pairs o f la te ra l grooves appear on segments 1-3 and delim it two longitudinal swellings along the la te ra l aspects o f these segments. The segmentation o f the body i s w ell marked, p articu la rly towards the p osterior end. A deep depression appears on the dorsal su fface o f 21 University of Ghana http://ugspace.ug.edu.gh 22 the 1 1 th segment. Ventrally th is segment also bears two small c ircu la r tepreasioas^rjfMei®oister35orj:‘(3|'ir>aealiir:.tubercales are long and. sharply pointed,. (b) D. tenuipes ( i ) Eggs (F ig . 3 .A) Length 1.32 ± 0.03 (1.25 - 1.35) Width 0.33 - 0 .0 2 (0 .30 - 0.35) The eggs are sim ilar to those o f D. thoracica in general appearance, but the anterior part i s smaller in diameter than the p oster io r end. The anterior knob, which i s elongated i s separated from the rest o f the egg by a s lig h t depression. 'The p oster io r knob i s rounded. Both knobs bear minute cup-shaped grooves. ( i i ) Larvae F irst Ins tar Length 1.49 --0 .0 1 (1 .47 - 1.52) Width 0.31 - 0.03 (0 .26 - 0.35) Length o f C.S. 0.25 - 0.02 (0 .22 - 0.28) The f i r s t in sta r larva o f I), tenuipes i s quite sim ilar to that o f S. thoracica . I t i s white, cy lin d r ica l and has a forked t a i l . The prothoracic sp iracles are absent but the p oster io r sp iracles are present. The t a i l i s rounded and bear minute hairs. These hairs are forked at th e ir extrem ities. University of Ghana http://ugspace.ug.edu.gh FIG. 3. DIOPSIS TENUIPES A. EGG, DORSAL VIEW a THIRD INSTAR LARVA C. PUPA, DORSAL VIEW University of Ghana http://ugspace.ug.edu.gh cUniversity of Ghana http://ugspace.ug.edu.gh 24 Second Instar length 4.59 - 0.51 (4 .05 - 5-68) Width 0.53 - 0i04 (0 .48 - 0.62) Length o f C.S. 0.82 - 0.03 (0 .77 - 0.96) The second in sta r resembles the f i r s t in sta r, but i t i s more cy lin d r ica l and has both prothoracic and p osterior spiracles.. The t a i l end is blunt and the hairs at the end o f the t a i l are forked but th icker than in the f i r s t instar. Third Instar (F ig . 3-B) Length 8.44 - 0.05 (8.36 - 8.52) Width 1.53 - 0.10 (1 .42 - 1.-68) Length o f C.S. 1.08 - 0'.03 (1 .04 - 1-13) The general structure i s as found in the second in star, but the larva has a stumpy appearance and i s almost cy lin d r ica l throughout i t s length. The tracheal trunks and the sp iracles are sim ilar to those D. thoracica . The t a i l i s very short and cone-shaped with blunt ends. The hairs at the end o f the t a i l are th ick and forked at th e ir extremi­ t ie s . ( i i i ) Pupae (F ig . 3.C) Length 5.80 - 0.06 (5.71 - 6.00) Width 1.65 - 0.08 -(1.60 - 1.70) The pupa i s o f the exarate form. I t i s cy lin d r ica l, pointed at both ends and white in colour. The anterior and p oster ior tubercules University of Ghana http://ugspace.ug.edu.gh are, however, dark. There are twelve segments, but the segmentation is often d i f f i c u l t to see due to the presence o f a white powdery sub­ stance. She f i r s t three segments gradually increase in width p oster io r­ ly to give a triangular appearance to the dorsal aspect o f the thorax which also slopes anteriorly . Two subdorsal grooves are found on segments 2-3 and d ivide the dorsal aspect o f these segments in to three parts. The pa ir o f anterior spiraeular tubercules are long and are placed d orso -la tera lly on the f i r s t segment. The sp iracles appear as n ipples on the tubercules. The p oster ior tubercules are cy lin d r ica l, stumpy and blunt at the ends. (c ) D. ichneumonea ( i ) Eggs (P ig . 4 .A) Length 1.89 - 0.02 (1 .85 - 1.95) Width 0.43 - 0 .04 (0 .40 - 0.45) The eggs are very s im ilia r to those o f D. thoracica but they are longer. The anterior knob is triangular while the p oster ior knob i s rounded. Both knobs are preceded by minute n ipples. ( i i ) Larvae F irst Instar Length 1.61 ± 0.06 (1 .58 - 1.68) Width 0.32 - 0.02 (0 .29 - 9.34) Length o f C.S. 0.19 - 0.01 (0 .17 - 0.20) The larva has a general structure quite sim ilar to the larvae o f University of Ghana http://ugspace.ug.edu.gh D. thoracica and 3D. tenuipes. The pro thoracic spirafcles are absent, but the p osterior sp iracles are present. The t a i l i s cy lin d r ica l and bear fin e hairs which are forked at their extrem ities as found in D. tenuipes. ' Second Instar Length 8.08 - 0 .24 {1 .8 3 - 8.96) Width 0.98 - 0 .04 (0 .90 - 1.17) Length o f C.S. 0.61 - 0.05 (0 .52 - 0.68) The structure i s as found in the f i r s t in sta r, but prothoracic sp iracles are present. The hairs at the end o f the t a i l are very th ick and forked. Third Instar (p ig . 4.B) Length 12.97 - 0.21 (12.80 - 13.15) Width 2.01 t 0 .04 ( 1 .9 5 - 2 .1 0 ) Length o f C.S. 0.79 - 0.01 (0 .77 - 0.81) The th ird in sta r is creamy white. I t i s cy lin drica l only from segments 4-12 and i s pointed in the anterior d irection . The sp iracles are sim ilar to those o f D. tenuipes.. The t a i l i s ionger than that o f D. tenuipes and the two halves are cy lin d r ica l with blunt ends. The hairs at the end o f the t a i l are th ick and forked at th e ir extrem ities as found in D. tenuipes. ( i i i ) Pupae (P ig. 4-C) Length 7.86 ± 0.06 ( 7.80 - 7.91) Width 1.99 ± 0.07 (1.90 - 2.10) 26 University of Ghana http://ugspace.ug.edu.gh 27 FIG. 4.. A. B. C. DIOPSIS ICHNEUMONEA EGG, LA TERAL VIEW THIRD INSTAR LARVA PUPA, DORSAL VIEW 2 mm University of Ghana http://ugspace.ug.edu.gh The pupa i s subcylindrical and. white with a powdery substance. The f i r s t three segments slope anteriorly as in B. tenuipes. There i s also a p a ir o f subdorsal grooves on segments 2 - 3 . The anterior end o f the f i r s t segment i s notched. The pa ir o f anterior spiraeular tubercules are in the same p osition as in D. tenuipes and bear n ipples as w e ll. The p oster ior spiraeular tubercules are con ica l at th e ir bases but are terminated by short tubular parts. 4 .2 .3 Description o f the Adults , AH the Diopsis species recorded in th is dudy appear reddish brown in colour when viewed dorsa lly . The ventral surface o f the abdomen i s cream or orange depending on the species. The thorax is black in a l l the species. The head i s triangular when viewed dorsally and i t s la te ra l sides have two long eye stalks bearing the pair o f compound eyes. Quite c lose to the eyes i s a pa ir o f 3 - segmented antennae w ith long b r is t le s . The o c e l l i are arranged triangularly on the head. V entrally the head bears a deep groove and a p a ir o f short but sharp spines. The mouthparts are the sucking type and when the insect i s feeding the proboscis i s seen as an elongated grooved structure with a c ircu la r ora l d isc. The cervix i s short and i s follow ed by a rounded thorax whichfcbears three pairs o f hairy jo in e d legs each with s ix tarsa l segments. The 28 University of Ghana http://ugspace.ug.edu.gh second and th ird femora have very sharp apical spines. The p leu rote3>- g ite bears a pa ir o f short spines and quite c lo se to these are the p a ir o f halteres. There i s a scutellum towards the p osterior end o f the thorax and th is bears a pair o f long sharp spines. The wing venation E H Mi s reduced. The costa i s complete. 2 + 3 , 4 + 5 and 1 + 2 reach the margin o f the wing. The cubitus and anal veins are absent. The abdomen con sists o f four segments. I t i s very slender at the anterior end and enlarges towards the p osterior extremity. (a) D. thoracica (P late I .a) Body length o f both sexes 8.09 - 0.19 (7 .50-8 .50 ) Intern-orbital distance o f Biale 13.1-8 i 0.61 (12.00-14-20) In te r -o rb ita l distance o f female 11,69 - 0.40 ( l 1.00-12.25) This species exh ibit sexUal dimorphism with regard to the in te r o rb ita l distance.- When measurements were taken on the in te r o rb ita l distance o f - f i f t y males and f i f t y females co lle cted from the f ie ld , the mean distance was found to be 13.18mm and 1 1 .69mm resp ective ly . A t - t e s t showed that the d ifferen ce was h ighly s ig n ifica n t (p = 0.01) (Appendix 3 ). The adult D. thoracica has a general reddish colouration but the dorsal aspect o f the p osterior end o f the abdomen i s deeper red. The scu telloa i s also red with red scu te lla r spines bearing numerous hairs. The abdomen i s bell-shaped, has a cream ventral surface, and i s covered 29 University of Ghana http://ugspace.ug.edu.gh PLATE 1 B Diopsis spp A - D. thoraciaa B - D. tenuipes C - D. ichneumonea University of Ghana http://ugspace.ug.edu.gh University of Ghana http://ugspace.ug.edu.gh with thick hairs. The f i r s t femora are not swollen and the wings have a ligh t brown colour with no spots. (k) tenuipes (P late 1 .B) Body length o f both sexes 7.36 - 0 .07 (6 .60 -7 .90 ) In ter o rb ita l distance o f both sexes 7.72^0.18 (7 .50-7 -93) \ This species exh ibit no sexual .dimorphism with regard to the in ter o rb ita l distance. I t has a reddish appearance and the dorsal aspect of the extremity o f the abdomen i s deep red as found in D. th oracica . The ventral surface o f the abdomen is cream but often assumes an orange colour in the gravid females. I t d if fe r s from D. thoracica by possessing a black seutellum. The seu te llar spines are red with dark apices. The abdomen i s less hairy? the f i r s t femora are not swellen, but the wings have black spots at th e ir apices. (c ) D. ichneumonea (P late 1.C) Body length o f both sexes 6.28 - 0.05 (6 .20 - 6.39) In ter o rb ita l distance o f both sexes 4-36 - 0 .07 (4 .25 - 4-45) Like D. tenuipes th is species exh ibits no sexual dimorphism with regard to the in te r o rb ita l distance. I t s s ize is quite c lo se to that o f D. tenuipes but the eye stalks are very short. I t s colour is much sim ilar to that o f D. thoracica and D. tenuipes but in contrast to these two species the dorsal aspect o f the t ip o f the abdomen is dark. .The seutellum is black and the seu te lla r spines are yellow ish . The f i r s t femora are swollen and th© wings have pre -ap ica l black spots. University of Ghana http://ugspace.ug.edu.gh 32 , (d) Diopsis sp d. , Only a few specimens were found in the f ie ld . I t resembles D. thoracica in several aspects but exh ibits great variations in the body s ize . The acutellum i s dark and the abdomen i s less hairy . Like D. ichneumonea i t has a swollen f i r s t femora, but the wings have no black spots. 4 .2 .4 Keys fo r the Id en tifica tion o f the Developmental Stages o f D iopsis spp ( i ) Key, fo r the id e n tifica t io n o f eggs o f Diopsis 1 • Egg length exceeding 1 .50mm ................................ 2 Egg length le ss than 1.50mm............ . .3 2., Terminal knobs preceded by n ipples; anterior knob tra in - gular; p osterior knob rou n ded Diopsis ichneumonea Dahl. Terminal knobs not preceded by n ipp les; anterior knob f la t and wider than long, p osterior knob pointed ............. D iopsis thoracica Westwood. 3. Terminal knobs not preceded by n ipples; anterior knob longer than wide; p oster ior knob rounded . . . . . . D iopsis tenuipes Westwood. ( i i ) Key fo r the Id en tifica tion o f Third Instar Larvae o f D iopsis 1. T a il with blunt ends ...................................... ............ . .2 T ail elongated, th ick at the base and with a sharp apex; University of Ghana http://ugspace.ug.edu.gh Body length 17 - 19mm ........... Diopsis thoracica West- wood. 2. Body cy lin d r ica l throughout the length, not sharply pointed anteriorly ; t a i l cone-shaped; Body length 7 - 9nnn............... D iopsis tenuipes Westwood. — Body cy lin d r ica l only from segments 4 - 1 2 , sharply pointed anteriorly ; t a i l cy lin drica l}. Body length 11 - 14mm D iopsis ichneumonea Dahl. ( i i i ) Key fo r the Id en tifica tion o f the Pupae o f Diopsis 1. Pupa white in c o l o u r ........................................... . . . 2 — Pupa brownish red dorsally , cream ven trally ; anterior spiracular tubercules situated ven trally ; p oster ior spiracular tubercules with very sharp ends; length. 10 - 11mm........................... Diopsis thoracica Westwood. 2. Anterior end o f f i r s t segment notched; anterior spiracu­ la r tubercules situated d orso -la tera lly ; p oster io r spira­ cular tubercules con ica l and terminated by a short tubu­ la r part; length 7 - 8mm Diopsis ichneumonea Dahl. — Anterior end o f f i r s t segment not notched; anterior spiracular tubercules situated d orso -la tera lly ; p oster ior spiracular tubercules cy lin d rica l with a blunt end; length 5 - 6mm................... Diopsis tenuipes Westwood. University of Ghana http://ugspace.ug.edu.gh ( iv ) Kev fo r the Id e n tifica tio n o f Adult D iopsis 1 . F irst femora swollen ................. 2 F irs t feroora not swellen ...................... .3 2. P air o f wings with one black sport each, spots sub-apical .................... D iopsis ichneumonea Dahl. Wings without any black spot ............... D iopsis sp d, 3. P a ir o f wings with one black spot each, spots ap ica l; scu te lla r spines with black apices ................. D iopsis tenuipes Westwood. Wings without any black spot; s ca te lla r spines reddish throughout th e ir lengths; abdomen very h a i r y .................. Diopsis thoracica Westwood. 4 .2 .5 O viposition Habits (a ) D. thoracica ti Mating could not be observed. The preoviposition period lasted fo r 14 - 17 days (mean = 15-4 days). Descamps (1957) observed that the fanale copulates several times in her l i f e time. The eggs were la id singly around the middle o f the upper surface o f the subterminal leaves, o ften in the grooves o f the m idrib. A few eggs were la id on the undersurface o f the leaves. Sometimes two eggs were found together, ly in g p a ra lle l to each other. On young plants almost a l l the eggs were confined to the leaves. I t was observed in 34 University of Ghana http://ugspace.ug.edu.gh the f ie ld that when the r ic e reached a height o f about 60cm most o f the eggs were la id on the sta lk about 5 - 20cm above s o i l le v e l. In the laboratory the to ta l number o f eggs la id by a s in g le female ranged from twenty-six to fourty-three with an average o f th irty -tw o. This was spread oyer a period o f one week. Up to f i f t e e n eggs could be la id by a sin gle female in a day, but i t was more usual to observe 6 - 10 eggs per day'. Sometimes sgg laying was interrupted by a day during which no ov iposition oeeured. Most o f the females died 1 - 3 days a fte r the la s t ov ip os ition . When such in sects were d issected they were found to contain 5 - 1 5 eggs, fo r example the female that la id fourty-three eggs contained s ix eggs, a fte r death. I t was observed that more eggs were la id between the hours o f 9-00 a.m. - 12.00 p.m. and 3.00 p.m. - 6.00 p.m. (b ) D. tenuipes Unlike D. th oracica , D. tenuipes chose in fested stalks fo r ov ip os ition . In cages with both healthy and "deadheart" stalks the la t te r always received more eggs. Most o f the eggs were la id at the bases o f the subterminal leaves in the grooves o f the midveins, very c lo se to the lig u le s . They were la id s in gly but up to f iv e eggs were occassion a lly found together at the same spot. In the f i e ld i t was common to fin d eggs o f J). tenuipes la id around cuts made on the r ic e stalks by rodents o r the entry holes o f lepidop- terous borers. Sometimes such holes were plugged with the eggs o f 35 University of Ghana http://ugspace.ug.edu.gh D. tenuipes. The maximum number o f eggs la id by caged in sects was found to be twenty-seven per female, spread over twelve days, with 1 - 3 eggs a day. (c ) D. ichneumonea The egg laying behaviour could not be studied in d e ta il, since on ly a few specimen were availab le . The eggs were deposited in the grooves o f the subtem inal leaves o f healthy sta lk s, around the middle o f the upper surface. 4 .3 B iology o f Bpilachna s im ilis Muls. 4 -3 .t L ife Cycle The eggs hatch in 4 - 5 days a fte r laying'. The larvae emerged by making s l i t s at the apices o f the eggs. The young larvae fed in groups mostly on the lower surface o f young r ic e leaves leaving the upper epidermis. The la te r in star dispersed to other r ic e p lants to feed. The feeding ctaused death o f the leaves and in severe in fes ta tion the whole plant died. Old r ic e leaves were scarcely attacked. There are four larva l instars and th e ir durations are summarized in table 2. When ready to pupate the larva fix ed i t s e l f o ften to the under­ surface o f the le a f by the anal end. Pupation lasted fou r days. The adult emerged by breaking the lin e along the p oster ior end o f the pxqaal pronotum. University of Ghana http://ugspace.ug.edu.gh 37 The adult fed on r ic e leaves in the same way as the larvae. Table 2 Summary o f the duration o f the immature stages o f E. s im ilis STAGE DURATION II DAYS .(mean)') (SD) (range) Egg 4.3 ± 0 .3 (4 - 5) Larva 14.6 ± 1.1 (12 - 17) 1st in sta r 3 .6 ± 0 .2 (3 ~ 4) 2nd « 3 .2 t 0 .4 (2 - 4) 3rd " 3 .4 ± 0 .2 (3 - 4) 4th " 4 .4 - 0 .3 (4 - 5) Pupa 4.0 ± 0 .0 ( 4 - 4 ) Egg - Adult 22.9 t 1.6 20 - 26 4 -3 .2 D escription o f the Immatore stages o f Epilachna s im ilis Muls ( i ) Eggs (P late 2.A) Length 1.20 ± 0.02 (1 .18 - 1.28) Width 0.42 1 0.02 ( 0 .37 - 0 .45) The eggs are cone-shaped and are la id mostly on the lower surface o f r ic e leaves in batches o f 15 - 55; mean = 36. When fresh ly la id they are bright yellow in colour but turn dark as they approach e& losion' University of Ghana http://ugspace.ug.edu.gh They are very shiny but have minute brown nipples a l l over the surface. These nipples increase in s ize towards the tip o f the egg; th is gives the extrem ities o f the eggs a brown colouration . ( i i ) Larvae The four larva l instars have the same general appearance. The larvae have a pcrrcupine-like appearance, the body being clothed with spines. The body i s ova l, widest at the th ird abdominal segment and narrower p oster io r ly than an teriorly . I t i s convex on the dorsal surface and almost f la t on the ventral aspect. The head is heavily s c le ro tized and deeply pigmented. I t i s connected to the thorax by a moderately long cervix. The ep icranial suture i s Y - shaped and indicated 'by a lig h ter colou ration . The arms o f the two fron ta l sutures ran almost stra ight from the anterior end o f the coronal suture to the bases o f the antennae. There are three o c e l l i on either side o f the head. These are arranged triangularly at the bases o f the antennae. The antenna is 3 - segmented with a w ell developed base. The clypeus bears a few setae on the la tera l margins. The m axilla bears a long 3 - segmented m axillary palpus. The thorax bears three segments, the prothorax being longer but smaller in diameter than e ith er o f the other two segments. The mesotho­ rax and the metathorax are sim ilar in shape'. The prothorax bears two pairs o f s c o l i while the mesothorax and the metathorax bear three pairs each, the pairs being symmetrically arranged on e ith er s ide o f University of Ghana http://ugspace.ug.edu.gh the median ecdysial line on a ll the three segments. Only the meso thorax hears a pair o f spiracles. These are situated dorsally at the anterio- lateral part of the segment. Each thoracic segment bears a pair o f legs which are a ll similar. Each leg bears setae and is terminated by a claw. The abdomen consists of ten segments. Each of the f ir s t eight segments bears three pairs of scoli and a pair o f spiracles. Kapur (1950) has assigned names to the three pairs of scoli on the thoracic and abdominal segments. He referred to the soolus near the mid-dorsal line as the dorsal scolus, next to i t i s the subdorsal scolus and the third, situated farthest:J: from* the mid-dorsal line and usually on the lateral margin, is called the dorso-lateral scolus (H g .5 ) . Each abdo­ minal spiracle is situated anterio-lateral relative to the base of the sub-dorsal scolus. The Mntfa segment i s semi-circular in shape. The tenth segment is short, whitish, directed dowiwards and forked at i t s end. Segments 9 and 10 bear short setae on their ventral surfaces. The four instars vary in size, colour, and number of spines per scolus. girst Instar (Pig.6.A) Width of head capsule 0.42 * 0.02 (0.40 - 0.45) Length of body 2.44 - 0.05 (2.40 - 2.48) Width of body 0.60 - 0.80 mm; mean = 0.67mm. The larva is grey on the dorsal surface, light orange on the ven- 59 University of Ghana http://ugspace.ug.edu.gh FIG. 5- ABDOMINAL SEGMENT OF EPILACHNA SIMILIS SHOWING THE POSITIONS OF THE SCOLI ( DIAGRAMATIC ). A. DORSAL SCOLUS B. SUBDORSAL SCOLUS C. DORSO - LATERAL SCOLUS University of Ghana http://ugspace.ug.edu.gh tral surface and h«g a brown head. The scoli on the protborax hear 4 - 6 spines each. The mescthoracic and metathoracic acoli bear three spines each except the dorao-lateral scoli which bear only one spine each. The abdominal scoli bear 2 - 5 spines each but the dorso-lateral scoli bear only one spine each. Second Instar Width of head capsule 0.62 - 0.05 (0.56 - 0.69) Length of body 2.95 - 0.12 (2.80 - 5-05) Width o f body 1.10 - 0.09 (0.90 - 1.41) The larva is deep grey and more pigmented than the f ir s t instar. A ll other features are quite similar to the f ir s t instar. The prothora- cic scoli have 4 - 7 spines each while the mesothoracic-and metathoracic 4 - 6 spines each. The dorso-lateral scoli of the thoracic and abdominal segments bear one spine each. Third Instar Width of head capsule 0.76 - 0.02 (0.70 - 0.79) Length of body 4.45 - 0.02 (4.40 - 4.50) Width of body 1.57 - 0.04 (1.51 - 1.45) The larva is very deep grey dorsally with a bright orange ventral surface. The other features are again quite similar to those found in the fir s t and second instars. The scoli on a ll the thoracic segments bear 8 - 1 0 spines each except the dorso-lateral scoli which have 4 - 6 spines each. The abdominal scoli bear 4 - 6 spines but the dorso-lateral University of Ghana http://ugspace.ug.edu.gh scoli bear 2 - 4 spines each. Fourth Jnstar (Fig.6.B; Plate 2B) 42 Width of head capsule 1.11 ± 0.05 (1.03 - 1-17) Length of body 7.27 - 0.03 (7.05 - 7.35) Width of body 2.78 - 0.04 (2.70 - 2.83) This is the only instar with a bright yellow colour on both the dorsal and ventral surfaces. The thoracic scoli bear 8 - 1 3 spines each while the abdominal scoli have 6 - 1 0 spines each. A ll dorso­ lateral scoli bear 4 - 10 spines each. ( i i i ) Papa (pig.6.C; Plate 2C) Length 6,64 - 0.14 (6.45 - 6.98) Width 3.46 t o.25 (3.10 - 3-85) The pupa is o f the exarate form. I t is broad at the anterior end, pointed at the posterior end and convex on the dorsal aspect with a fla t ventral surface. The larval exuviae are pushed back to the anal extre­ mity exposing the head, pronotum and 4 - 7 pup&l segments. When freshly formed the exposed parts are yellowish, but later turn cream and finally black before mergence of the adult. The developing head is bant downwards leaving the pronotum at the anterior extremity. 7entrally the head, antenae, compound eyes and legs are seen folded together. The pair of wings are triangular in shape and are arranged along the lateral sides of the body. Dorsally each exposed segment bears a pair of round pigmentation University of Ghana http://ugspace.ug.edu.gh FIG. 6. EPILACHNA 3MILK A. FIRST INSTAR LARVA & FOURTH INSTAR LARVA €5 C. PUPA. ( LARVAE DRAWN WITHOUT THE SCOLI ) UJUJ University of Ghana http://ugspace.ug.edu.gh A B PLATE 2 University of Ghana http://ugspace.ug.edu.gh EPILACMA su n n s A - Eggs B - Fourth Instar Larva C - Pupa D - Adult University of Ghana http://ugspace.ug.edu.gh 4 .5 .3 . Key fo r the Id en tifica tion o f Larval Instars o f 1. s im ilis 1. D orso-lateral s c o l i o f mesothorax, metathorax and abdominal segments with only one spine each ....................... 2 D orso-lateral s c o l i o f mesothorax, metathorax and abdominal segments with two o r more s p in e s .................... . 5 2. Head capsule width not exceeding 0.50mm; bases o f s c o l i swollen ......................... F irs t Instar. Head capsule width exceeding 0.50mm; bases o f s c o l i not s w o lle n ................. Second Instar. 5- Larva o f deep grey colour; head capsule width 0 .7 - O.&am; d orso -la tera l s c o l i o f meso thorax, metathorax, and abdominal segments with 2 - 6 spines each ................ Third Instar. - Larva o f bright yellow colour; head capsule width 1 - 2mm; d orso -la tera l s c o l i o f mesothorax, metathorax, and abdominal segments with 4 - 1 0 spines each Fourth Instar. 45 along the subdorsal lin es. 1’he exposed parts o f the body bear h airs which are more pronounced on the pronotum and wings. 4»3.4 Description o f Adult E. s im ilis (P late 2.D) Width o f head 1.09 ± 0 .0 4 (1 .00 - 1.32) Length o f body 5.97 ± 0.05 (5 .78 - 6.05) University of Ghana http://ugspace.ug.edu.gh The adult i s reddish brown a i l oyer the body. I t i s convex on the dorsal surface and f la t ven tra lly . The head i s very small and i s p a r tia lly concealed try the pronotum. The mouthparts which are o f the b itin g type are not so conspicuous. The mandibles are very short, dark at the edges and possess many teeth . The labium i s ve iy small with comparatively long 3 - segmented la b ia l palps. The- m axilla i s ventral to the mandibles and la tera l to the labium. I t i s cy lin d r ica l ahd bears a 3-segmented club-shaped m axillary palp. The antenna bears eleven segments. I t i s clavate and s lig h t ly geniculate. A p a ir o f black compound eyes are situated ju st p oster io r to the antennae. The prothorax i s mavable and larger than the mesothorax o r the metathorax. The legs are short and usually folded under the body, 4 .3 .5 O viposition Habits Copulation occurs any time during the day and each female mates several times in her l i f e time. The p reov iposition period i s 4 - 8 days (mean = 5.8. days) When egg-laying began i t continued without interruption with one batch o f egg a day fo r 2 - 3 weeks. Beyond th is period breaks o f 1 - 5 days were noticed . Occasionally, two batches o f eggs were la id on the same day, but the maximum number o f eggs per day never exceeded s ix ty . The tota l number o f egg batches la id varied from 1 0 - 4 0 per female. The number o f eggs per batch increased with subsequent ov ip os ition up to University of Ghana http://ugspace.ug.edu.gh a pealc o f 46 and then dropped gradually. The to ta l number o f eggs la id varied from 229 to 797 per mated female. The individual that produced 797 eggs la id them in 40 batches over a period o f 46 days. The eggs are la id with a dark brown cementing substance which holds the batch to the le a f . Unmated females la id eggs but these were in smaller batches and were scattered since they have l i t t l e o r no cementing substance. Such eggs sh rive lled and did not hatch. The unmated females stopped laying a fte r a few days. I t was observed that some mated females did not lay eggs at a l l o r la id fo r a few daj's and stopped. Such in d iv i­ duals stopped feeding and hid themselves between the r ic e s ta lk s. Some insects remained in th is state fo r as long as four months. Mating i s quite frequent when the sexes are paired. Where females were allowed to mate only once they produced f e r t i l e eggs fo r about a month, but thereaster a l l eggs la id were in fe r t i le . 4 .4 Discussion 4-4.1 D iopsis spp The in a b il ity to rear D iopsis larvae on cut r ic e stalks i s a serious lim itation to the mass rearing o f the species. The use o f potted r ice seedlings is cumbersome. There i s therefore the need to develop a su itable a r t i f i c ia l rearing' method. Generally, the descriptions and the b iology o f these in sects agree favourably with the observations o f Descamps ( 1957a; b ) . In the present work additional information has been provided by describing the d ifferen t 47 University of Ghana http://ugspace.ug.edu.gh larval instars o f the three species. Based on the mode o f feeding Descamps ( 1957a) has divided the larvae o f D iopsis spp into two major groups, v iz ;— 1. Those exhibiting Obligatory phytophagy 2. Those exhibiting optional phytophagy. Obligatory phytophagy i s further subdivided into tw o:- (a) Larvae feeding only on liv in g sta lks and which cannot be maintained at any stage in th e ir l i f e on decaying vegetable matter. Into th is group can be placed D. th oracica . ( b) Larvae feeding on l iv in g stalks fo r the f i r s t few days and which can la te r thrive on decomposing vegetable matter. The species iH th is subgroup include D. ichneumonea. , Optional phytophagy i s exhibited by D. tenuipes. The larva o f th is species can ex is t in three d iffe re n t ways:- (a ) As phytophagous larva in the same way as D. ichneumonea. This o ften occurs when the eggs are la id on healthy sta lks. (b ) As a saprophyte, when the eggs are la id on already attached p lants. Thi3 i s the most predominant mode o f larval l i f e in the f ie ld . (c ) As a predator on other larvae which i t comes into contact with. The a b ility dio feed on several r ic e stalks during the larva l l i f e makes D. thoracica very destructive to the r i c e crop. The larval l i f e i s comparatively longer than D.. tenuipes and D. ichneumonea and as much as s ix stalks can be destroyed by a single larva. The a b ility to f lo a t University of Ghana http://ugspace.ug.edu.gh in the irr ig a tio n water means that every availab le r ic e h i l l could be attacked. The mechanism o f plugging the groove above the anterior end o f the pupa with a white foamy substance is probably in defence against natural enemies. I t was observed that the pupae are heavily parasitized in the f ie ld . Unlike D. thoracica , the larvae o f D. tenuipes and D. ichneumonea complete th eir l i f e in one sta lk and th erefore destroy fewer sta lk s. The larval cannibalism o f D. tenuipes observed in the laboratory has also been reported by Descamps ( 1957b). He found in the f i e ld , larvae o f D. tenuipes feeding on each other and on young larvae o f other pests such as D. th oracica , Antherigona spp and Sesamia spp. 4.4*2 Epilachna s im ilis Apart from the short notes on the l i f e cy cle o f E. s im ilis provided by a few e a r lie r workers such as Maxwell-Lefroy (1909), Smithers (1957) and Schmutter (1969), there appears to be no detailed study o f th is species. The descriptions o f the various stages o f th is insect can only be compared with the general account on the subfamily Epilachninae (Coleoptera; C occinellidae) given by Kapur (1950)* Such a comparison does not reveal any marked deviation from the general observations on the subfamily. I t has been pointed out that many females o f E. s im ilis did not lay eggs or la id eggs fo r a short time and then withdrew from a l l forms 49 University of Ghana http://ugspace.ug.edu.gh o f a c t iv ity to hide in between the r ic e sta lks. This behaviour has already been described by Maxwell-Lefroy (1909) as a form o f hibernation the purpose o f which is to await better conditions fo r egg laying. He also points out that egg• laying i s more p r o l i f i c when the adults are w ell fed. University of Ghana http://ugspace.ug.edu.gh 5. SEASONAL POPULATION CH.4XQES 5.1 Materials and Methods With irr ig a tio n f a c i l i t i e s double cropping per year i s the p ra ctice o f i-ice cu ltiva tion in the Accra P la in s. These seasons are usually September to February and. la rch to July. However, to achieve a con ti­ nuous cropping cy cle fo r the purpose o f th is tudy tr ip p le cropping was done at both Kpong and Dawhenya fo r systematic sampling from March 1971 to A pril 1972. The two l i c e farms fo llow d iffe ren t cu ltu ra l p ractices but at fa r as p o ss ib le , a uniform method was adopted f o r the sampling. At each cropping an 0 i4 hectar p lo t o f s ize 45 metres x 25 metres was chosen. At Kpong the r ic e seeds sere d r ille d at a rate o f approxi­ mately 90 kilograms per h ectar! and the f i r s t sampling was done two weeks a fte r germination. At Dawhenya the seeds were nursed fo r twenty days and then transplanted at a spacing o f 25cm x 25cm inches with four seedlings per p oin t. Sampling was started two weeks a fte r transplanting. On both farms subsequent samplings were carried out at regular in terva ls o f fourteen days u n til the grains were fu l ly r ip e . Sampling fo r eggs, larvae and pupae o f D iopsis spp was done by removing f i f t y r ic e h i l l s from the p lo t on each sampling day. Leaving out a, border o f 1 metre the h i l l c lo se st to the toe a fte r every tenth pace (one pace, was approximately 50cm) in e ith er d irection was sampled. ’tShere a h i l l was missing the next was se lected . This method gave 10 h i l ls University of Ghana http://ugspace.ug.edu.gh length wise and 5 M ils breadthwise. At each sampling the heights o f 20 plants, measured from the so il level to the highest point, were taken and the mean calculated, The same plots were used to sample for E. sim ilis. This was done by eiaminiwg 50 iioe h ills , selected at 10 paces in either direction, for eggs, larvae and pupae. To get an estimate of adult Diopsis spp and E. similis populations net sweeping was done. Such sweepings were carried out at 9,00 am on each v is it . Previous sampling had shown that more insects are caught at this time of the day, when they are very active. Muslin nets o f 40cm diameter and a depth of 60cm were Used. There were 100 sweeps per plot, counting as one sweep each swing from right to le ft and back. These sweeps were taken along the width o f the plot after evexy ten paces. The nets were emptied after every tenth sweep. In the laboratory the species were separated and sexed by examination of the genetalia. On the day of sampling the rice h ills were examined in the laboratory and h ill and stalk infestations were recorded. These were expressed as percentages. The stalks wesedissected to record the .eggs, larvae and pupae of Diopsis spp. These were separated into species with the aid of a binocular microscope. Distinction was made between infestations caused by diopsid and lepidopterous borers. In infestations due to lepidopte­ rous borers frass is always present on the stalks; diopsid borers never show such a symptom. Rice h ills or stalks which had "deadhearts" , 5'2 University of Ghana http://ugspace.ug.edu.gh "whiteheads" or contained, larvae or pupae, but had no visible sign of attack were recorded as infested. At harvest 50 rice h ills per plot were sampled to record the number of panicles and "whiteheads". From these the percentage panicle and "whitehead" were calculated. 5.2 Seasonality of Diopsis spp. Stalk infestation by lepidopterous borers at both Kpong and Dawhenya remained very low and never exceeded 2 . 9 In contrast to this, infestation by diopsids reached a maximum of 46.4$ at Dawhenya. The lepidopterous borers recorded were Sesamia spp. (Lepidoptera; noctui- dae), 6hilo spp (Lepidoptera; pyralidae) and Maliarpha separatella Hag. (Lepidoptera; pyralidae). The results of the systematic samplings are shown in tables 3 - 1 4 and fig s . 7 - 1 2 . The infestation followed a similar trend at both Kpong and Dawhenya. The fir s t samplings at two weeks after transplanting never failed to show infestation. Infestation then rose sharply and reached a peak when the plants were 58 - 72 days old. The percentage "whiteheads" for the three croppings are tabulated for comparisons with the maximum infestations in table 15. On the whole more rice stalks were damaged in the major rainy season. The most dominant Diopsis species was D. thoracica followed by D. tenuipes; D. ichneumonea and Diopsis sp. d were very rare. Figs. 8 University of Ghana http://ugspace.ug.edu.gh Table 3 Diopsis in festation on rice at Kpong March - June 1971 Date Age of Rice (Davs) Mean Height (cm) Mean Ho. of stalks per h ill fo Infestation Diopsis Species H ill Stalk D. thoracica D. tenuipes E* L P E L P 11-3-71 17 26.1 2 .0 8.3 4.0 3 1 - - - - 25-3-71 31 36.5 2.9 20.0 1 1 .8 5 4 - 2 - - 8-4-71 45 50.5 3.2 56.0 28.8 13 7 - 2 - - 22-4-71 59 65.2 5.2 58.0 22.0 3 10 2 3 3 - 6-5-71 73 72.8 6.8 54.0 18.2 2 6 8 - 2 2 20-5-71 87 106.4 6.9 52.0 13.3 - 3 7 - 3 3 3-6-71 101 113.8 6.5 54.0 15.2 - 1 2 - 1 5 17-6-71 115 126.8 6 .1 24.0 5.4 - 2 2 - 3 2 Total - - - - - 26 34 21 7 12 12 * E = Eggs, 1 = Larvae, P = Pupae $2 University of Ghana http://ugspace.ug.edu.gh Table 4 Diopsis in festation on r ice a t Kpong July - September 1971 Date Age of Bice (Davs) •H „ If I Mean No. of stalks per h ill io Infestation Diopsis Species S ill Stalk D. thoracica D. tenuipes E L P E L P 1-7-71 30 44-5 3.5 46.0 ■ 17.5 19 12 - - 1 - 15-7-71 44 52*6 5.3 56.0 21.3 29' 13 2 - - 1 29-7-71 58 56.1 6.8 80.0 25-5 10 16 11 4 1, 3 12-8-71 72 79.9 i 7*3 64.0 18.8 18 9 14 7 3 4 26-8-71 86 98.7 9.8 60.0 15.0 11 4 8 4 - 3 5 9-9-71 100 106.4 10.4 74.0 16.3 4 2 5 3 2 6 23-9-71 114 124.3 10 .2 64.0 14.2 - - 3 - 4 8 Total - - - - 91 56 43 18 14 27 University of Ghana http://ugspace.ug.edu.gh Table 5 Diopsis infestation on rice a t Kpong November 1971 - February 1972 Date Age o f ' Sice (Days) Mean Height (cm) Mean No. of stalks per h ill $ Infestation Diopsis Species - Hill Stalk D. thoracica D. tenuipes E L P E L P 16-11-71 16 25-7 2 .1 8 .0 3.9 4 - - - - - 30-11-71 30 41.5 4.3 14-0 5.2 6 2 - - - 14-12-71 44 51.9 6.3 30 .0 7.2 10 4 - 5 1 - 28-12-71 56 67.7 7.4 . 42.0 1 1 .0 4 6 1 9 2 - 11- 1-72 72 77.5 8 .1 44.0 9 .4 7 9 3 6 4 2 25- 1-72 86 104.4 7.6 40.0 9.1 2 4 6 3 2 4 6- 2-72 100 124.8 6.9 30.0 5.7 - 1 4 _ 2 5 22- 2-72 114 130.9 6.5 34.0 5.9 - 2 2 - - 2 Total - - - - - 33 28 16 23 11 13 University of Ghana http://ugspace.ug.edu.gh Table 6 Diopsis in festation on riee at Dawhenya April - Jmly 1971 Date Age of Bice (Days) Mean Height (cm) Mean No. of stalks per h ill io Infestation Diopsis Soecies Hill Stalk D. thoracica D. tenuipes E* 1 P E L P 1-4-71 15 26.3 6.5 6.0 2.3 - - - - - - 15-4-71 29 42.3 10.9 36.0 5.2 3 - - - - 29-4-71 43 61.0 16.0 46.0 12.5 10 3 - 7 2 - 13-5-71 57 66.2 16 .2 60.0 17.1 14 7 - 18 5 - 27-5-71 71 76.4 15.8 58.0 21.3 6 12 2 23 9 4 10-6-71 85 80.1 16.1 58.0 10.7 4 10 6 13 . 12 4 24-6-71 99 102.5 15.7 56.0 8.3 5 3 8 8 4 6 8-7-71 113 109.3 ' 15.9 54.0 7.0 - 1 3 12 2 3 Total - - - - - 42 36 19 81 34 17 University of Ghana http://ugspace.ug.edu.gh Table 7 Diopsis Infestation on rice at Dawhenya July •• October 1971 Age of Mean Mean Ho. $ Inf estation Dionsis Soecies Date fiice Height of stalks Hill Stalk D. thoracica D. tenuines (Days) (cm) uer h ill E L P E L P 8-7-71 16 25.0 6.3 10 .0 2.5 4 1 - - » 22-7-71 30 40.3 11.3 40.0 6.0 17 11 - - - - 5-8-71 44 60.1 15.7 94.0 21.9 59 . 51 1 7 3 - 19-8-71 58 68.2 15.3 100.0 48.4 15 55 19 16 8 1 2-9-71 72 75.3 14.0 100.0 35.4 22 6 40 33 4 8 16-9-71 86 ■ 81.5 15.3 98.0 30.4 12 3 38 - 8 12 30-9-71 100 104.5 15.4 80.0 10.9 4 2 6 - 9 7 14-10-71 114 1 10 .2 14.1 72.0 7.3 - 2 2 - 2 5 Total - - - - - 131 131 106 56 34 33 University of Ghana http://ugspace.ug.edu.gh fab le 8 Diopsis in festation on rice at Dawhenya December 1971 - April 1972 Date Age of Bice (Days) Mean Height (cm) Mean No . of stalks tier h ill io Inf estation Diopsis Soecies H ill Stalk D. thoracica E. tenuipes E L P E L P 29-12-71 15 24.5 5.8 2 .0 0 .7 - - - - - - 12-1-72 29 41.2 1 1 .0 6 .0 2 .1 - - - - - 26-1-72 43 60.9 15.9 20.0 6.3 3 - - - - - 9-2-72 57 67.8 16.6 28.0 11.5 8 9 - - 1 - 25-2-72 72 73.6 16.3 40.0 13.4 13 10 7 6 3 2 8-2-72 85 83.7 15.0 38.0 12 .1 2 6 11 8 3 7 22-3-72 99 107.3 14.8 32.0 10 .0 5 2 4 5 1 3 5-4-72 113 113.1 14.3 30 .0 5.8 - 1 3 - 3 2 Total - - - - - 31 28 25 19 11 14 University of Ghana http://ugspace.ug.edu.gh PE R CE N TA G E IN FE S TA TI O N 90 FIRST CROP SECOND CROP THIRD CROP OF JUNE RICE AUGUST SEPTEMBER NOV. DAYS JANUARY FIG. 7. POPSIS INFESTATION AT KPONG ; MARCH 197! TO FEBRUARY 1972. a\C University of Ghana http://ugspace.ug.edu.gh PIG 8 ABUNDANCE OF DIOPSIS T HORACICA AT KPONG , MARCH 1971 TO FEBR UAR Y DIOPSIS NUMBERS PER BO HILLS I i'9 SECO N D University of Ghana http://ugspace.ug.edu.gh DI OP SI S N U M BE RS PE R BO H IL LS F IRST CROP SECOND CROP TH IR D CROP A PRIL f l i C E AUGUST SEPTEM BER NOV. D A Y S D ECEM BER JANUARY FIG 9. ABUNDANCE OF DIOPSIS TENUIPES AT KPONG., MARCH 1971 TO FEBRUARY 1972 G\ TO University of Ghana http://ugspace.ug.edu.gh P e r c e n t a g e in f e s t a t io n 14 AGE O F R IC E IN DAYS APRIL MAY JUNE JULY AUGUST SEPTEM BER OCTOBER JANUARY FEBRUARY MARCH APRIL FIG. 10 DIOPSIS INFESTATION AT DAHWENYA ; APRIL 1971 TO APRIL ©72 University of Ghana http://ugspace.ug.edu.gh sum 09 U3 of the stalks in the fie ld . As stated by Schroder (1971) and confiimed in this investigation infestation starts when the plant is a few weeks old. At this stage the rice plant has the ability to t ille r to compensate for the lost stalks. In the opinion of Akinsola (1970) this process of compensatory tillering could be enough to over­ come the effect o f the infestation and thus there might not be any appreciable loss in yield. To test the validity of this theory an investigation was conducted under controlled conditions. The main aim was to assess the effect of D. thoracica on tillering and yield at various stages o f growth of the riee plant and at different intensities of stalk infestation. ' 7.1.1 Materials and Methods The methods etqaloyed for this experiment were modified from Eok and Varghese (1966a). The experiment was carried out from 10th August 1971 to 2nd January 1972 in an insect-proof greenhouse with a glass roof and walls made o f 0.2mm wire mesh. The temperature and relative University of Ghana http://ugspace.ug.edu.gh humidity ranges within the green house were 23 .5 -30 .8 C (mean = 25 . 6°C) and 6 5 -8 ^ (m m = 7S^) respectively. Seeds of the rice variety C4 - 63 were nursed in the green house on 2ist July and transplanted on 10th August 1971, ^hen thqjr were 20 days old, into wooden boxes measuring 40cm x 40cm at the bottom and 40cm in height, Bach box was f i l le d to a depth of 30cm with so il of the Black clay series . In it ia lly six seedlings were planted per box but this was thinned down to four after 21 days. The level of water above the so il was maintained between 3 - 5om throughout the experiment. Ireshly hatched larvae of D. thoracica were used for the infestation . The rioe stalks were a r t if ic ia lly infested by introducing the larvae with the aid of a camel hair brush. The larvae were watched t i l l they bored into the sta lk . The layout was a fact oriel experiment embo<3ying rice plants at three age groups and fiv e intensities of larval infestation . Tbs re were a to ta l of fifteen treatments in a randomized, block design with four replicates. The plant age groups were:- (1) 21 days after transplanting ( 2) 60 days after transplanting (3) 90 days after transplanting The intensities of larval infestation were as fo llowa:- ( 1 ) ($ intensity - Control ( 2) 23^ B 1 larva to 4 t i l le r s 8ft University of Ghana http://ugspace.ug.edu.gh (3) 50^ intensity - 1 larva to 2 tille rs (4) 75$ " 3 larvae to 4 tille rs (5) 10Q$ " - 1 larva to 1 t i l le r . The records taken were:— (i) ' The number of t ille rs at the time o f infestation ( i i ) The number of t ille rs after 30 days o f infestation ( i i i ) The number of infested t ille rs after 30 days o f infesta­ tion (iv) The number of t ille rs at maturity (v) The number of panicles at maturity (vi) The number of "whiteheads" at maturity (v ii) The clean grain yield. Prom ( i i ) and ( i i i ) the percentage stalk infestation after 30 days was calculated. The percentage "whitehead" was calculated from (v) and (v i) . To prevent re-infestation the plants were checked 35 days after infestation and any pupae formed were removed. The grains were harvested on 2nd January when they were fu lly ripe. .Analysis o f variance based on maximum tille rs at maturity and clean grain weight were carried out. Differences between the effects of the age and intensity of infestation were tested with the Duncan's Multiple Bange Test. University of Ghana http://ugspace.ug.edu.gh 7 .1 .2 Observations and Results The recordings are summarized in table 20. Table 21 and 2% show the effects of the treatments on the tillering and grain yield respectively The analysis o f variance on the tillering and yield are summarized in appendices 4 and 5. Plants infested at 21 days old showed the deadheart symptom within one or two days while at 60 days or 90 days the symptoms showed after four days. At 21 days old the 100 infestation killed most o f the stalks before they could produce t i lle r s . In changing stalks most larvae selected new tille rs . Plants infested at 21 days never showed the "whitehead" symptoms which was most prevalent on plants infested at 60 days. The treatments had highly significant effects on the tillering and yield and there were high interactions between age and intensity of infestation. Tillering was increased by infestation intensities of 25$ and 50$ but decreased by the 75$ and 100$ levels. The increase or decrease was more pronounced when infestation was on 21 day-old plants. The yields showed that the controls were significantly better than a ll the other- treatments. I'he loss in yield was proportional to the increase in intensity of infestation. University of Ghana http://ugspace.ug.edu.gh Table 20 Artificial Infestation of Rice Stalks with Larvae of D. thoracica AT INFESTATION 30 DAYS AFTER INFESTATION AT MATURITY Treatment No. of Tillers No. of Larvae Nov. of Tillers Infested Tillers % Infes­ tation No. of Tillers No* of Pani­ cles No. of White­ head White­ head Grain Yield (gm) % Loss in Yield +++ + x ++ 21 x 0 4 0 10 0 0 21 18 0 0 90.25 0 21 x 25 4 1 14 4 28.6 24 19 0 0 81.50 9.15 21 x 50 4 2 11 6 54.5 23 20 0 0 72.00 20.23 21 x 75 4 3 10 6 60.0 15 10 0 0 51.75 42.66 21 x 100 4 4 6 6 100.0 14 11 0 0 39.25 56.51 60 x 0 17 0 20 0 0 22 21 0 0 81.00 0 60 x 25 16 4 18 . 13 i « . l 22 20 2 10.0 76.00 6.17 60 x 50 17 9 21 *5 23.8 21 16 2 12.5 70.25 13.27 60 x 75 16 12 19 22 14 3 21.4 59.50 26.54 60 x 100 17 17 20 A 30.0 23 17 9 52.9 62.25 23.15 90 x 0 22 0 22 0 0 23 21 0 0 89.50 0 90 x 25 22 6 23 4 17.0 22 20 2 10.0 76.75 14.24 90 x 50 21 11 20 6 30.0 21 20 1 5.0 75.00 16.21 90 x 75 20 15 22 9 40.9 22 19 2 10.5 70.00 21.79 90 x 100 21 21 24 12 50.0 22 * 17 1 5.9 70.25 21.51 figures represent the means of four replications. + - Age of Bice in Days. ++ - Percentage stalk Infestation. +++ - AS io of yield in Control. University of Ghana http://ugspace.ug.edu.gh Table 21 Effect o f In ten sities and Age o f Infestation with Larvae o f D. thoraoieia on T illerin g o f Eioe $ Infestation Age of Eice (Days) Average Effect o f Infes­ tation 21 60 90 0 Age x Infestation Means 21 22 23 22 25 24 22 22 23 50 23 21 21 22 75 15 22 22 20 100 14 23 22 20 Average Effect of Age 19 22 22 , I Duncan's Test on the Effect of different rates of larval infestation cn the tillering of rice plants infested at 21 days o ld :- Infestation level 100$ 75$ Control 50$ 25$ Mean Wo. of Tillers 14 15 21 23 24 Any two means not underscored by the same line are significantly different at the 1$ level. Any two means underscored by the same line are not significantly different at that level. University of Ghana http://ugspace.ug.edu.gh Table 22 Effect e f Intensities and. Age of Infestation with Larvae 8§ of D. thoracicia on Held o f Bice (gm) % Infestation Age of Sice (lays) Average Effect of Infes­tationi 21 60_ . 90 0 Age x Infestation Means 40.3 81.0 89.5 86.9 25 81.5 76.3 , 76.8 78.1 50 72.0 70.3 75.0 72.4 75 51.8 59.5 70.0 60.4 100 39.3 62.3 70.3 57.3 Average Effect of Age 67.0 69.8 76.3 ( i ) Duncan's Test on the average effect of the level of larval infesta­ tion on grain yield of rices- Infestation level 100$ 75^ 50$ 2% Control Mean yield (gm) g7.5 60,4 72.4 78.1 86.9 ( i i ) Duncan's Test on the average effect of age. of larval infestation on Ihe grain yield of rice:* Age of Inf estation 21 days 60days 90days Sean yield (gm) 67.0 69.8 76.3 A ll the differences between means in both ( i ) and ( i i ) were signifi­ cant at the 1 fa level. University of Ghana http://ugspace.ug.edu.gh 7-1.3 Discussion The results of the experiment clearly illustrate that significant yield losses were caused by the infestation, but the extent of losses sass dependent both on the age when infestation occured and the intensity o f infestation. 21 days-old plants infested at 23$ inten­ sity were less seriously affected because they had a chance of recover­ ing by producing new tille r s . Actually plants at this age and inten­ sity of infestation produced more tille rs as compared to the control. However, the yield was lower because many o f the tille rs did not carry grains or bore smaller panicles. A comparison between the yields at 60 days and 90 days indicated that the former suffered heavier losses at a ll the different rates of infestation. At 60 days old the rice plant no longer has the ability to t i l le r , but is comparatively fresh to support the larvae. At 90 days, survival of the larvae on the plants is expected to be lower. The yields estimated under these controlled conditions are not the same as those expected in the fie ld because the plants could be limited in their growth. However, these results can be regarded as indicative of the minimum effects on yields due to Diopsis thoracica infestation. 7.2 Food Preference and Survival Tests with Larvae of S. si m-i ii s Prom the literature i t is known that E. similis feeds on various University of Ghana http://ugspace.ug.edu.gh cereal crops. In section 6 two important cereals of Ghana, maize and sorghum were recorded as altenate hosts to this insect. The aim of the following two experiments was to find nut which of the major cereals is most preferred and to ascertain i f a ll o f thesa could support E. similis to maturity. 7.2.1 itood Preference Test ( i ) Materials and Methods Leaves of two weeks old seedlings o f the four cereals, rice, maize, sorghum and millet were used as test materials. Strips of leaves measuring 0.5cm x 9cm were hung in 3cm x lOem glass vials by fixing the strips to the cork stopper with pins. Pour strips were hung in each vial and they were o f the following combinations:- A. Kice alone - 4 strips of the leaves B. Maize alone - " " " " H C. Sorghum alone - " " " '• " D. M illet » - " " « » « E. Rice + Millet - 2 strips each o f the leaves P. Eiee + Maize - " " " " " " G. Kice + Sorghum - " " " " " *' 1 . Maize + Millet - " " " " " " I . Maize + Sorghum - n " « n i. m J. Millet + Sorghum — " " « « »> « K. sice + Millet + Sorghum + Maize - 1 strip each of the leaves. 91 University of Ghana http://ugspace.ug.edu.gh The strips were hung in such a way that they were about 1cm. from the bottom of the vial and did not touch each other nor the sides o f the vial. Pour freshly merged fir s t instar larvae of E. similis starved for twenty-four hours were placed at the bottom of the v ia l, which was kept upright throughout the experiment. The number of larvae feeding on each strip of leaf was recorded after one hour. ( i i ) Observations and Results Larvae were observed to move along the sides of the v ia l. At the top they walked on the surface of the cork t i l l they came into contact with a suitable leaf. Once feeding had started the larvae scarcely moved further. In A, B, C, and D which contained only one species of test plant each the larvae were observed to feed on the food offered. Observations in combinations E - K are tabulated below.(Table 23). A plus sign indicates that the leaf was fed on and a minus sign indicates that there was no feeding. Figures following the plus signs show the total number of larvae found feeding on the leaf after one hour. There was a marked preference for maize and sorghum as compared to rice. Millet was fed on only in A where the larvae had no choice. University of Ghana http://ugspace.ug.edu.gh 93- Table 23 Food, preference in the Larvae of E. similis Combination Test Plants E Bice Millet +4 F Bice Maize +1 +3 a Rice Sorghum +2 +2 E Maize Millet +4 i Maize Sorghum +3 +1 j Millet Sorghum +1 +3 K Rice Millet Sorghum Maize +1 +3 7.2 .2 Survival Test ( i ) Materials and Methods Two weeks old potted seedlings o f rice, sorghum, millet and maise were used. On each potted plant was put one freshly emerged first instar larva of E. similis and the plant covered with a lantern glass globe of size 10 x 15cm. There were ten sets of this experiment for each species of test plant. The number of larvae that remained alive on each of the test plants was recorded- at 2 days intervals. The University of Ghana http://ugspace.ug.edu.gh duration o f the instars was also noted. ( i i ) Results All the larvae on rice, sorghum and maize survived. Survival on millet was, however, poor. Only two out o f the ten larvae pupated. The duration o f the instars is summarized in Table 24. Table 24 Mean Duration o f Larval Instars o f E. similis on Four Major Cereals of Ghana Instar Mean Duration of Instar (Days) Bice Sorghum Millet Maize 1 3.3 2.2 4.2 3.1 2 2.8 2.3 3.6 2.1 3 3.3 3.1 3.4 2.2 4 4.2 3.2 5.0 3-2 Total 13.6 11.8 16.2 10.6 Larval development was more rapid on maize tout delayed on m illet. All larvae that p lated emerged as adults and there was no difference in the duration of the pupae. 7 -2 .2 Discussion In the fir s t experiment i t was noted that the larvae of E. aimilia University of Ghana http://ugspace.ug.edu.gh Maise, Sorghum, Sice, M illet. The results of the second experiment support the findings in the f ir s t experiment. There was high survival on the crops which are preferred. The low preference and the low survival observed on millet may be due to the inability of the larvae to move freely on the surface o f the leaves. The leaves of this crop, are very hairy and could impede larval movements. can feed on any o f the four crops, but exhibit some preference which was in the order: - University of Ghana http://ugspace.ug.edu.gh 8.1 Diopsis spp. I t is evident front the foregoing account that the diopsids can be very destructive to rice in the fie ld . Diopsis thoracica in parti­ cular poses a threat to the cultivation of this crop in the area investigated. A single larva of this pest per h ill o f rice could reduce grain yield by as much as 9 .15S&. In the rainy season when almost every h ill is attacked, and there are often 2 - 4 larvae per h il l , the total grain loss will be very high. The compensatory tille r ­ ing induced by these borers in the rice does not appear to have any l appreciable advantage when the infestation is heavy, because under such a situation the plant cannot cope with the attack. Furthermore the overlapping generations in the fie ld can lead to reinfestation and these new tille rs w ill be destroyed. Van Halteren (1970) concluded that there was no need to adopt any control measures against D. thoracica. Over 4&A stalk infestation was recorded at Dawhenya in the rainy season. Such a level of infestation can lead to heavy losses in yield and attack by Diopsis spp cannot therefore be ignored completely. Chemical control of the diopsids isI likely to prove d ifficu lt since the larvae occur, for most of their l i fe , in the stalks. Since eggs are more liable to come into direct contact with chemicals an insecticide with ovicidal properties w ill be more efficient. Applications might be timed to protect the crop 8 . CONCLUSION University of Ghana http://ugspace.ug.edu.gh at the more vulnerable stages of growth; for instance from a week or two after transplanting to two months. I t is likely that systemic insecticides will be more effective. The use of resistant varieties of rice which is one of the major approaches to the control of lepidop­ terous stem borers can as well, be adopted against diopsid borers. A physical feature of rice such as tight sheaths will make i t very difficult for larsae to enter or leave the stalks. Both Schroder (1971) and Simmonds (1970) have stressed the use of biological control methods against these larval borers. This i s quite feasible and probably will not involve much expenditure since a number of natural enemies were recorded in the present investigation. Risbec (1956) has also given a comprehensive l i s t of parasites of the diopsid borers in the Camerouns. An integrated control approach embracing some of these outlined methods seems to be the most appropriate. 8.2 Epilachna similis The damage caused by E. similis at Kpong is very low and may not be economically significant. I t is only at the beginning of the rainy seasons that some precautions may have to be taken. Rice nurseries in particular will require some protection against this pest. The larvae, which are the most destructive to the crop, are exposed on the leaves and can therefore be easily killed by spraying an insecticides. The pest occurs in short outbreaks only at the early l i fe of the crop. University of Ghana http://ugspace.ug.edu.gh Thus the plants can be sprayed once or twice at the beginning o f the t cropping seasons. 98 University of Ghana http://ugspace.ug.edu.gh 9. LITERATURE CITED Akinsola, E.A. (1970). The incidence of stem-borer damage on swan® rice in Northern Nigeria and the control of the species con­ cerned. Paper presented to the lest African Rice Research Seminar, I .I .T .A ., Ibadan, Nigeria March 1970. Anon, (1969). Rice stem-borers in Asia. GIBA Agrochemicals, Techni­ cals, Monograph No. 1 March, 1969, Pages 40-45- (1970). Pest control in rice. PINS Manual No.3, Ministry of Overseas Development, Pages 119—191 * Brammer, H. (1967). Soils of the Accra Plains Soil Research Institute (C .S .I.R .) Memoir No.3- Pages 1-5, 10—11. Breniere, J. (1966). Dix annees de recherches sur les ennemis du riz en Afrique Francophone et a Madagascar. L'Agron. Trop. 2J_(4) : 514-519. - (1969). Importance des probities entomologiques dans le deve- lopement de la riziculture de L'Afrique de L'ouest. L'Agron. Trop. 24(10) : 906-927. Descamps, M. (1956). Insects nuisibles au riz dans le Nord-Cameroun. L'Agron. Trop. JJ. s 732-755. _________ , ( 1957a). Contribution a L'etude des Diptere3, Diopsidae nuisibles au riz dans le Nord-Cameroun. Journal d'Agric. Tropical et de Botaniqua Appliquee. J.(l-2) ; 83-93. _________ , ( 1957b). Recherches morphologiques et biologiques sur les Diopsides du Nord-Cameroun. Ministrie Prance Outre Mer. Sect. Techn. Agr. Trop. Bulletin Scientifique No.7. 154pp. Ghartey, F.N. (1970). Rice production and extension. The 1970 fihgnq Agricultural Conference on Rice Production. Information and Publication Unit, Ghana Ministry of Food and Agriculture. Pages 71-79. Imms, A.D. (1965). A General Textbook of Entomology, 9th ed. Methuen, Lond. Pages 602-605- 1 Jerath, M.L. (1965)- Rice pests and their known parasites and predators in Nigeria. Federal Dept. Agric. Ibadan, Nigeria, Memoradum No. 86. Jordan, F.J. (1956). An investigation into the presence and prevalence of rice stem-borers and their parasites in Sierra Leone. Report of Rice Res. Station, Rokupr, S. Leone. University of Ghana http://ugspace.ug.edu.gh Kok, L.T. and S. Varghese ( 1966a). Yield losses due to Lepidopterous stem-borer:- infestation on rice (Oryza sativa). Trop. Agric. 4£(l) : 69-73. Kok, L.T. and Varghese, G. ( 1966b). Assessment o f rice stem-borer infestation - A case study in North Malaya. Trop.'Agric. 43 (4) : 331-334. Lever, R.J.A.W. (1969). The current position on the control o f insect pests of rice. CIBA Agrochemicals, Technical Monograph Bo.1 March, 1969, Pages 32-38. Maxwall-Lefroy, H. (1909). Indian Insect L ife :- A manual of Insects of the Plains^-Thacker and Co. Calcutta and Lond. Pages 303-309. Morgan, H.G. (1970). Insect pests of rice in Sierra Leone. Paper Presented to the West African Sice Research Seminar, Ford Foundation, Nigeria, March, 1970. Peacock, A.D. (1914). Entomological pests and problems of Southern Nigeria. Bull. Ent. Res. 4 : 191-220. Sisbec, J. (1956). Les parasites des insectes borers du r i z - an Cameroun. Agron. Tropicale 11(2) ; 234-247. Schmutter, H. (1969). Pests o f North East and Central Africa with particular Reference to the Sudan. Gustar Fischer Verlag stuttgart. Portland. U.S.A. Pages 127-128. Schroder, D. (1970). Memorandum of the CIBC-West African sub-station, Kumasi. June 1970. _________ , (1971) ♦ Memorandum on the possibilities of biological control of some important insect pests and noxious weeds o f West African Commonwealth Countries, especially Ghana. CIBC West African Sub-station, Kumasi. March, 1971. Pages 42-44. Simmonds, F.J. (1970). Possibilities of biological control of Diopsids (Diptera): serious pest o f rioe in West Africa, Unpublished report of the CIBC. 5pp. Smithers, C.N. (1957). The recent outbreak of ladybird (Ep i^c^a similis Thb) on maize in Southern Rhodesia. Rhodesia Agric. Journal 54 : 332-336. Southwood, T.R.E. (1966). Ecological Methods. Methuen and Co. Ltd. Pages 189-191. Kapur, A.P. (1950). The biology and external morphology o f the larvae o f Epilachninae (coleoptera; Coceinellidae). B u ll. Ent. Res. 43. : 161-208. University of Ghana http://ugspace.ug.edu.gh Van Halteren, P. (1970). Insect pests of irrigated riee at A.S.S. Kpong. Ghana Parmer 14(2) ; 48. Walker, P.T. (1958). Insecticide studies on East African agricultural pests. Bull. Bnt. Bes. 48 : 341-347. Van Bruggen, A.C. (1961). A p a rtia l revision o f the Diopsidae or stalk-eyed f l ie s o f Southern Africa. South African Animal L ife 8 : 415- 439- University of Ghana http://ugspace.ug.edu.gh 10 . APPENDICES Appendix 1 M eteoro log ica l Data - Kpong Mar® Apr. May June July Aug. Sept. Oct, Nov. Bee. Jan. Feb. Aver­ age Mean Max. Temp. °C 3k 33 34 30 29 29 31 32 33 32 34 35 32 Mean Min. Temp. °G 23 23 22 22 21 21 20 19 20 19 21 23 21 Monthly ra in fa ll in can 14.58 5.50 6.60 15.98 14.30 11.28 12.88 20.55 1 .58 4.23 O .U 1 0 . 1 3 9.81 No. of rainy days 10 9 ;6 18 15 11 16 15 5 4 1 8 10 Mean BH at OJ.OOhrs 0 0 84 83 82 87 8| §5 7B n 8£ 8g 83 83 Mean BH at I5.00hrs. (fi) 69 71 74 75 67 70 71 69 69 67 68 69 70 University of Ghana http://ugspace.ug.edu.gh Appendix 2 Meteorological Data - Dawhenya 1971 Mar. May June July Aug. Sept. Oct. Nov. Dec. 1972 Jan, Feb. Mar. Aver age Mean Max. Temp. °C 33 33 32 28 28 30 31 34 35 36 35 33 32 Mean Min. Temp. °G 24 23 23 22 21 22 22 23 25 24 23 24 23 Monthly rainfall in cm 6.00 6.35 15.25 12.00 5.50 6.00 9.75 1.05 2.25 1 .50 3.73 6.04 6.29 No. of rainy dqys 6 7 13 7 5 7 8 4 2 2 2 5 6 Mean EH at 09.00 hrs (fo) 76 78 79 80 81 78 76 74 77 80 80 79 78 Mean BH at 15.00 hrs (^ o) 67 64 68 70 73 70 69 ■ 66 64 64 65 65 67 University of Ghana http://ugspace.ug.edu.gh 1 m Appendix 3 Summary of the t-te st on adult J). thoracica Length o f Body (mm) Males Females Inter-Orbital Distance (mm) Males Females No. Measured 50 50 50 50 Mean 8.09 8.03 13.18 11.69 Difference of Means 0.06 1.49 Standard Deviation (SD) 0.19 0.02 0.61 0.40 Combined SD 0.04 0.10 Degrees o f Freedom 49 49 49 49 Combined DF 98 98 Observed t 1.50 tfS 14 . 90** Required t 5$ 1.98 ' 1.98 \fo 2.63 2.63 Appendix 4 Analysis of Variance table for number o f rice tille rs at Maturity Source of Variation df ss ms Observed F Required F 1 5% \% Total for Treatments . 59 767<.65 Blocks 3 112.98 37.66 Treatments (14) 464.40 33.17 7.32** 1.94 2.54 Age of Bice (a) 2 114.10 57.05 12.59** 3.22 5.15 Infestation ( i) 4 68.57 17.14 . 3.78* 2.59 3.80 Interaction A x I 8 28.73 35.21 7.77** 2.17 2.96 Error 42 190.27 4.53 University of Ghana http://ugspace.ug.edu.gh 1 0 5 Appendix 5 A nalysis of Variance ta b le fo r elean grain y ie ld (gm) S ouree of df ss ms Observed 3? ■ required F Variation % 1?S Total for Treatments 59 17344.58 Blocks 3 2229.91 743.30 "Si n *J *1 « _• --J* - *• '-p Treatments Age of Sice (A) Infestation ( i) Interactions A x I (14) 2 4 8 8948.28 674.63 4300,66 3972.99 639.16 337.32 1075.17 496.62 16 1 ,40s# 85.18** 271.51** 125.41** 1 .94 3 .22 2.59 2.17 2 .54 5.15 3.80 2.96 Error 42 16 6 .3 9 3.96 Appendix; 6 Meteorological D a ta - Greenhouse Experiment August - December 1971 Month Monthly Mean Temp. °C- Monthly Mean EH (%) Min. Max 09.00hrs I5.00hrs August 1971 22.0 26.5 85 74 September 1971 22.3 27 .4 83 73 October 1971 23.1 28.6 80 72 November 1971 23.3 30.4 79 70 December 1971 23.5 30.9 82 67 University of Ghana http://ugspace.ug.edu.gh