EVALUATION OF PROPICONAZOLE (TILT) 
AND PRUNING IN THE CONTROI^OF.jBLACK
SIQATOKA DISEASE IN/QHANA
1< \ ! *(\ y
X f  r  #  ■*'...
0SP»s4S ’KWAS'J ZW /tKPU')
IN PARTIAL FULFILMENT OF THE REQUIREMENTS 
FOR THE HEGREEE OF MASTER OF PHILOSOPHY 
IHCROPSCIEHCE
NOVEMBER, 1997
CROP SCIENCE DEPARTMENT 
UNIVERSITY OF GHANA 
LEGON
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D E C L A R A T I O N
I hereby declare that, except for reference to other 
people's work which have been duly cited, this work is 
the result of my own original research and that this work 
has neither in whole nor in part been presented for 
degree in this University or elsewhere.
CEPHAS KWASI BODAKPUI
(STUDENT)
2£7 r.F’.Xf
DATE
DR. K. A. ODURO
(SUPERVISOR)
DATE
PROF. K.  -NUAMAH
(CO-SUPERVISOR)
DATE
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ABSTRACT
Pruning of diseased leaves and the use of 
Propiconazole (Tilt), a foliar fungicide with systemic 
properties, were two different recommendations made by 
the Ministry of Food and Agriculture to control black 
sigatoka, currently an important disease of plantain in 
the country. The two methods were evaluated from 
September 1995 to April 1997 at the University of Ghana 
Agriculture Research Station, Kade.
Four treatments, namely, Tilt (0.125g ai/L), 
Pruning, Tilt (0.125g ai/L) + Pruning and Control 
(neither Tilt nor Pruning), were applied in; an RCBD 
experiment.
The average height of the plantain in the different 
treatments were found not to be significantly different 
from each other. Using percentage total leaf area 
attacked, disease severity for the Control treatment was 
on the average 16% (13.1-19%) while it was 4.6% (2.6- 
6.2%),5.1% (3.7-6.4%) and 3.8% (2.5-5.0%) for Tilt,
Pruning and Tilt+Pruning respectively. The Control was 
significantly different from the other three treatments 
which were, however, not different from each other at 5% 
significance level.
Maturity of plantain was found to delay in the 
Control. The total number of bunches harvested at 66 
weeks were 54, 50, 52 and 47 with bunch weights of
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453.OKg, 3 9 2 .2Kg, 405.OKg and 249.lKg for Tilt, Pruning, 
Tilt+Pruning and Control respectively. The Control was 
significantly different from the other three treatments 
which were however not different from each other (p. 5%). 
The difference in bunch weight was due to significant 
difference in weight per finger (0.258Kg, 0.245Kg,
0.252Kg and 0.186Kg), respectively, for the treatments. 
There was no difference in the number of fingers per 
bunch which was on the average 26.1 for all the 
treatments. Correlation analysis gave a negative but a 
significant association (r = -0.96) between severity of 
disease and yield. Simple pruning and burning of diseased 
leaves could be recommended for the control of black 
Sigatoka in the absence of chemical which may be 
expensive.
To determine the potency of the chemical (Tilt), a 
bioassay was conducted in the laboratory. One ml of the 
following concentrations of Tilt viz. 0.0125g ai/L;
0.025g ai/L; 0.05g ai/L 0.0625g ai/L and 0.075g ai/L were 
incorporated into 5 different PDA in Petri dishes to form 
Tilt-ammended PDA media plus a control (only PDA). 
Ascospores from diseased leaves were ejected onto these 
plates. Germination in all cases started about 12 hours 
after ejection. Unipolar and bipolar germ tubes Were 
observed on all the plates but the percentages differ, 
depending on the concentration of Tilt. The higher the
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concentration, the lower the percentage germination. 
Visible growth was seen with the naked eye after 4 days. 
Aerial mycelia was whitish with reverse dark on the 
control plates while the aerial mycelia on Tilt-ammended 
PDA were gray with reverse dark. No conidia were seen in 
all cases after several weeks. The bioassay studies 
confirmed that Tilt was potent.
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ACKNOWLEDGEMENT
I with to express my profound gratitude to Dr. K. A. 
Oduro - Head of Crop Science Department, University of 
Ghana, Legon and Prof. K. Afreh-Nuamah - University of 
Ghana Agricultural Research Station (UGARS)- Kade under 
whose excellent supervision I wrote this thesis. Their 
constructive criticism, patience and encouragement made 
this work a reality.
I am indebted to Dr. K. G. Ofosu-Budu and Dr. J. K. 
Osei both of UGARS-Kade who freely volunteered 
information during the course of the project. I am also 
indebted to Mr. A. Ampomah and Mr. J. M. Kokroh - Farm 
manager and senior Assistant farm manager respectively, 
at UGARS-Kade, for their valuable help and contributions 
from the beginning to the end of the field work. I am 
grateful to Mr. Ayifa and wife, Sister Lydia Larbi, and 
the workers of UGARS-Kade, for their immense assistance 
whenever I went there.
My sincere thanks go to my course mates especially 
Messrs. Michael Assuah, Edmund Botchway, Gershon Wodzrah 
and Benard Boateng for their good company and 
encouragement during my stay at University of Ghana.
Finally, I thank Miss Favour Anyam who typed the 
script. To all who helped in one way or the other, I say, 
thank you. May the Almighty God bless you.
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D E D I C A T I O N
This work is dedicated to my wife, MRS. JOSEPHINE 
BODAKPUI, and my son, MARIUS EDEM FIIFI BODAKPUI.
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TART.K OF CONTENT
CONTENT
DECLARATION........................................... i
ABSTRACT..............................................ii
ACKNOWLEDGEMENT....................................... V
DEDICATION............................................vi
CHAPTER ONE : INTRODUCTION............................. 1
CHAPTER TWO: LITERATURE REVIEW........................ 4
2.1 Origin and importance........................... 4
2.2 The Pathogen.................................... 5
2.2.1 The Conidia stage............................ 6
2.2.2 The Perfect or Ascospore stage............... 6
2.3 Disease development and symptoms................7
2.4 Control......................................... 8
2.4.1 Cultural...................................... 8
2.4.2 Genetic improvement...........................9
2.4.3 Chemical control.............................. 10
2.5 Propiconazole..................................14
CHAPTER THREE: MATERIALS AND METHODS..................16
3.1 Fieldwork...................................... 16
3.1.1 Project site.................................. 16
3.1.2 Land preparation and treatments...............16
3.1.3 Planting material and planting................17
3.1.4 Research activities and records taken........ 17
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3.2 Bioassay studies in the laboratory..............22
3.2.1 Media Preparation............................. 22
3.2.2 Isolation of pathogen......................... 23
3.2.3 Data collected................................ 24
CHAPTER FOUR: RESULTS................................. 25
4.1 Fieldwork...................................... 25
4.1.1 Effect of the treatments on plant height
of plantain .................... 25
4.1.2 Effect of Tilt and Pruning on average number 
of leaves of plantain infected by black 
Sigatoka.................................... .25
4.1.3 Effect of Tilt, Pruning and amount of 
rainfall on severity of black Sigatoka....... 28
4.1.4 Effect of Tilt and Pruning on yield of 
plantain.....................................32
4.2 Bioassay in the laboratory for testing efficacy 
of the chemical (Tilt).......................... 38
4.2.1 Ascospore discharge........................... 38
4.2.2 Ascospore germination.........................38
4.2.3 Culture characteristics.......................43
CHAPTER FIVE: DISCUSSIONS............................. 48
5.1 Effect of Tilt and Pruning on height of 
plantain.......................................48
5.2 Effect of Tilt, Pruning and amount of rainfall 
on severity of black Sigatoka and yield of 
plantain at Kade............................... 49
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5.3 Efficacy of Tilt as evidenced in the Bioassay
studies........................................52
CHAPTER SIX: CONCLUSIONS AND RECOMMENDATIONS..........54
CHAPTER SEVEN: LITERATURE CITED..................... 55
APPENDICES:...........................  63
APPENDIX I ANOVA table for average number of
leaves 28 to 44 weeks after planting. . .63 
APPENDIX II ANOVA table for youngest leaf with 
symptom (YLWS) 28 to 44 weeks after
planting.............................. 64
APPENDIX III ANOVA table for average bunch weight...66
APPENDIX IV ANOVA table for average number of
fingers per bunch..................... 66
APPENDIX V ANOVA table for length of "middle"
finger................................ 67
APPENDIX VI ANOVA table for weight of "middle"
finger................................ 67
APPENDIX VII ANOVA table for disease severity from
week 8 to week 44...... 67
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T.TST OF FIGURES
FIGURE TITLE PAGE
1. Spraying Tilt 250EC with knapsack sprayer
on short plantain plants infected by black 
Sigatoka disease................................20
2. Spraying Tilt 250EC with motorised mist blower
on tall plantain plants infected by black 
Sigatoka disease................................ 21
3. Average plant height of plantain infected by
black Sigatoka disease.......................... 26
4. Effect of Tilt, Pruning and amount of rainfall
on black Sigatoka............................... 29
5. Effect of Tilt and Pruning on black Sigatoka
disease severity of 16-week-old plantain plants 
at Kade........................   30
6. Effect of Tilt and Pruning on black Sigatoka
disease severity of 24-week-old plantain plants 
at Kade.........................................31
7. Effect of Tilt and Pruning on black Sigatoka
disease severity of 32-week-old plantain plants 
at Kade....................................   .33
8. Effect of Tilt and Pruning on youngest leaf of
plantain to show symptom (YLWS) of black 
Sigatoka at different times......................34
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9. Number of bunches harvested from week 54 to
week 66......................................... 35
10. Ascospores of Mycosphaerella fijiensis from 
diseased plantain leaves discharged onto PDA.... 39
11. Germination of ascospores of Mycosphaerella 
fijiensis of plantain on PDA.....................40
12. Germination of ascospores of Mycosphaerella 
fijiensis of plantain on 0.0125g ai/L Tilt- 
ammended PDA, 12 hours after discharge onto the 
media................   40
13. Germination of ascospores of Mycosphaerella 
fijiensis of plantain on 0.05g ai/L Tilt- 
ammended PDA, 12 hours after discharge onto the 
media. ..........    41
14. Germination of ascospores of Mycosphaerella 
fijiensis of plantain on PDA, 12 hours after 
discharge.......................................41
15.. Germination of ascospores of Mycosphaerella 
fijiensis of plantain on PDA, 24 hours after 
discharge...................................... .
16. Culture of Mycosphaerella fijiensis from 
diseased plantain leaves growing on PDA......... 46
17. Culture of Mycosphaerella fijiensis from 
diseased plantain leaves growing on 0.0125g 
ai/L Tilt-ammended PDA...........................
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T.XST OF TABLES
TART.K TITLE PAGE
1. Average number of leaves of plantain infected
by black Sigatoka from week 8 to week 44..........27
2. Yield and components of yield 66 weeks after 
transplanting....................................36
3. Percentage germination of Mycosphaerella 
fijiensis ascospores dischared from diseased 
plantain leaves on different concentrations of 
Tilt-ammended PDA................................ 42
4. Average length of germ tube of Mycosphaerella 
fijiensis ascospores discharged from diseased 
plantain leaves (um)............................. 44
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CHAPTER ONE 
INTRODUCTION
Plantain (Musa paradisica L) is a major source of 
carbohydrate for millions of people in the developing 
world (Stover and Simmonds, 1987; Swennen, 1990). In 
Ghana it was estimated that the national production 
between 1986 and 1990 was 5,205,617 metric tonnes 
(Ministry of Food and Agriculture, PPMED, 1990).
Plantain is affected by a number of diseases caused 
by viruses, bacteria and fungi. One of the fungal 
diseases which has caused serious losses of friuts in 
many countries is the leaf spot (Sigatoka) disease 
(Wardlaw, 1961). This disease is caused by the fungus 
Mycosphaerella sp. There are two types of the disease, 
namely, the yellow and black Sigatoka. The yellow 
Sigatoka, caused by M. musicola, was first reported in 
Fiji in 1912 (Philpott and Knowles, 1913). The black 
Sigatoka is caused by M. fijiensis, (Paracecospora 
fijiensis) and tends to be more serious was observed in 
1960 in Fiji. It was named by Rhodes (1964) as black leaf 
streak, but it was later re-named black Sigatoka 
(Wardlaw, 1972).
Black Sigatoka disease was observed in some West 
African countries including Ghana in 1985 (Wilson, 1986) 
and it became epidemic in the 1990s (Hemeng et al 1995).
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Oduro et al (1992) reported that the national incidence 
of the disease was 62.5% and recommended pruning and 
burning of diseased leaves as one of the control 
measures.
Yield losses of plantain due to black sigatoka range 
from 20% (Pasberg-Gauhl, 1989) up to 50% (Stover, 1983; 
Mobambo, 1993). Mobambo et al (1993) also reported that 
plantain yield losses of 33% in the first and 76% in the 
second cropping cycle had been estimated at Onne, 
Southeastern Nigeria.
To control the disease in Ghana, Oduro et al (1992) 
recommended pruning and burning of diseased leaves. In 
1994 the Ministry of Food and Agriculture recommended the 
use of Propiconazole (Tilt), a fungicide, for the control 
(Boadu, 1994). Tilt 250 EC (Emulsifiable Concentrate) is 
a broad spectrum foliar fungicide with systemic 
properties. The active ingredient content is 250g 
propiconazole per liter. Even though Tilt has been uesd 
successfully in the Central Americas (Molina and Salas, 
1990), there has been conflicting reports from farmers 
concerning its effectiveness (Afreh-Nuamah, personal 
communication). There was therefore the need to evaluate 
the two recommended control measures.
The objectives of this work, therefore, were:
(1) to evaluate the effect of the two recommendations,
namely the application of Propiconazole (Tilt) and
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Pruning on the severity of black sigatoka and yield 
of plantain.
(2) to test the potency of the fungicide (Tilt) in the 
laboratory.
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CHAPTER TWO
LITERATURE REVIEW
2.1 Origin and importance
Sigatoka disease takes its name from the Sigatoka 
valley in Fiji where severe damage was first recorded in 
1912 (Philport and Knowles, 1913). Black Sigatoka was 
first recorded as black leaf streak in Fiji in 1964 
(Rhodes, 1964). However the disease is thought to have 
originated in the Papua New Guinea - Solomon Island area 
and was widespread in the Pacific and Southeast Asia long 
before being recorded in Fiji (Stover, 1976; 1978). Black 
Sigatoga reached the Central America in the 1970s and it 
had a devastating effect on plantain production 
(Bustamente, 1983).
In Africa it was first reported in Zambia in 1973 
(Reameakers, 1975), but it was not until the early 1980s 
that it spread to Central Africa (Wilson and Buddenhagen, 
1986). It entered all East African banana-growing 
countries, except Uganda, between 1986 and 1989, where at 
least some important East African highland bananas were 
susceptible (Sebasigari and Stover, 1988; Swennen and 
Vuylsteke, 1988a). According to Wilson (1986), black 
Sigatoka was observed in some West African countries 
including Ghana in 1985. Hemeng et al (1995), however, 
said the disease became epidemic in the 1990s.
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Swennen and Vuylsteke (1988b) reported that all 
plantain cultivars found in Central and West Africa were 
susceptible. In addition some of the most popular banana 
cultivars of East Africa were susceptible (Swennen and 
Vuylsteke, 1991; Vuylsteke et al, 1993). Mobambo et al
(1993) noted that all known plantain cultivars collected 
from West and Central Africa, tropical America and Asia 
were susceptible to black sigatoka under Onne (Nigeria) 
conditions. Shillingford (1975) reported that all edible 
triploid (genome AAA) banana cultivars are susceptible 
and when the genome B is introduced (AAB and ABB), 
resistance in the triploid occurs, but Laville (1983) 
said the presence of a single genome rarely gives 
varieties resistance to Mycosphaerella fijiensis. 
Resistance seems to intensify only with genome ABB. 
However, the work of Foure (1985) has shown that this is 
not always the case.
2.2 The Pathogen
The fungus which causes the disease is 
Mycosphaerella fijiensis. According to Agrios (19&8) M. 
fijiensis belongs to the division of higher fungi called 
Ascomycotina (Ascomycetes or the sac fungi). They produce 
sexual spores called ascospores generally in groups of 
eight within an ascus. Its class is Loculoascomycetes 
(the ascostromatic fungi). They produce pseudothecia ie
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perithecium-like stroma with asci in a separate or single 
large cavity. Dothideales is its order. The fungus has 
two stages, the conidia and ascospores stages.
2.2.1 The conidia stage
The formation of conidia begins soon after the 
enlarging streaks or spots on the leaf have become dark 
brown but the presence of the darkish acervuli and 
conidia clusters is more easily detected in the buff-grey 
centres of older leaf (Wardlaw, 1972). Conidia may be 
found on both sides of the leaf, but are usually more 
abundant on the upper surface of unsprayed leaves.
The dissemination of conidia takes place only by action 
of rain or dew, and wind is effective in removing them 
(Wardlaw, 1972). The conidium in hyaline to olivaceous 
brown, straight to slightly curved, obclavate to 
cylindrical with truncate base thickened hilium, smooth 
wall and 5 to 11 septa. The size ranges from 33 to 153 x
1.7 to 4.9um (Mulder and Holliday, 1974).
2.2.2 The Perfect or Ascospore stage
Leach (1946) demonstrated the presence of the 
ascospore state of Mycosphaerella spp. Subseguent work 
showed that during the rainy seasons ascospore infection 
assumes considerable importance. Ascospore is more 
resistant than conidium and can be distributed by air
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current. It is, therefore, more important in the wide 
dissemination of the pathogen (Wardlaw, 1972). They are 
mostly found on the under surface of the leaf. The 
ascospore is hyaline, two-celled with one cell bigger 
than the other and has slight constriction at the septum. 
The size ranges from 13.2 to 19.8 x 3.3 to 4.9um with an 
average of 15.9 x 4.0 um (Mulder and Holliday, 1974). 
Jacome et al (1991) indicated that ascospres reguire free 
water or nearly saturated environment (RH of 98-100%) for 
germination and germ tube growth. Conidia, in contrast, 
germinate in a wider range (RH of 92-100%). Pasberg-Gauhl
(1994) reported that M. fijiensis is a very slow growing 
fungus in culture and it is time consuming to produce 
adeguate inoculum for artificial inoculation.
2.3 Disease development and Symptoms
The spores rapidly penetrate the stomata on the lower 
leaf surface by means of their germinative filament 
(hyphae) and thus colonise the mesophyll (Meredith, 1970; 
Stover, 1980; Belalcazar and Merchan, 1991). The evident 
feature of the disease is the presence of a profusion of 
small discrete spots on the lamina of leaves with areas 
of scorched or brown, leaf tissue where the spots are 
closely grouped together. For convenience, Foure (1986) 
divided lesion evaluation into six (6) different stages 
as follows:
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Stage 1 is the first external symptom of the disease. It 
appears as a small depigmented spot. These are not 
visible in transmitted light and can be observed only on 
the undersurface of the leaf. Stage 2 appears as a stripe 
generally brown in colour and visible on the undersurface 
of the leaf. In stage 3, the stripes become longer 
reaching 2 or 3 cm. Stage 4 of the disease appears on the 
undersurface as a brown spot and on the upper surface as 
a black spot. In stage 5, the elliptical spot is totally 
black and has spread to the undersurface of the leaf. It 
is surrounded by a yellow halo with the centre beginning 
to flatten out. Stage 6 is when the centre of the spot 
dries out, turns grey in colour and is surrounded by a 
well defined black ring, which is in turn surrounded by 
a bright yellow halo. These spots remain visible after 
the leaf has dried out.
2.4 Control
2.4.1 Cultural
The control of the Sigatoka disease has taken 
different forms since it was first noticed. In Venezuela, 
cultural methods of disease management such as removal of 
affected leaves and leaves hanging down the pseudostem to 
reduce inoculum levels were recommended. These were 
however either not practised or were being undertaken too 
infrequently. In addition, leaves with severe necrosis
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that had been removed were lying on the ground instead of 
being stacked in heaps to reduce the surface area of 
tissue that wouuld be liberating spores (Jones, 1995). In 
Ghana, Oduro et al (1992) also recommended pruning and 
burning of diseased leaves.
It has been reported (Bananuku abd Rubaihayo, 1994; 
Mobambo et al, 1994) that black Sigatoka is more severe 
on plants grown on soils with poor organic content. 
Mobambo and Naku (1993) therefore recommended the use of 
organic matter which helps to enhance plantain growth and 
thus reduce the effect of black Sigatoka on plantain in 
backyard gardens. Also, organic nutrients from the 
disposal of household waste may play a role in reducing 
black Sigatoka severity on backyard plantain (Mobambo et 
al, 1993). However the supply of organic matter in large- 
scale plantain plantation is still a problem (Nweke et 
al, 1988; Ruhigwa et al, 1994).
2.4.2 Genetic Improvement
The rapid spread of black sigatoka gave impetus to 
efforts aimed at the genetic improvement of Musa spp. 
(Persely and DeLanghe, 1987). Molina and Krausz (1988) 
also said the development of cultivars of banana and 
plantain resistant to black Sigatoka is imperative to 
control the disease economically. However, breeding 
plantain and banana is a very slow and tedious process
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due to problems with polyploidy, seed and pollen 
infertility. Also, low clonal multiplication rates, lack 
of variability and barriers to sexual hybridization 
impede genetic improvement.
Due to the apparent lack of resistance in the 
African Musa gene pool, black Sigatoka has become the 
overiding constraint to Musa cultivation and possess a 
major threat to food security in the plantain and banana 
growing regions of Africa (IITA, 1988). Chemical control 
was therefore recommended.
Chemical control strategies of the disease arc 
possible and exist but according to Mobambo et al (1993), 
they are not feasible or are socio-economically unsound 
because the bulk of the crop produced in Africa is by 
resource-poor family farmers who cannot afford the 
expensive imported fungicides. For example, the cost of 
chemical control of the disease in bananas grown for 
export in Central and South America is approximately $100 
million annually (UPEB, 1985). Ramsey et al (1987), also 
indicated that the cost of controlling yellow Sigatoka in 
Northern Queensland, Australia could be as high as 14% of 
the total production cost.
Different fungicides have been tested and in various 
degrees, have been found to possess practical value. In
2.4.3 Chemical control
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early works in Fiji, the oil Dithiocaramate emulsion was 
used against sigatoka, but maneb as a water based spray 
gave better disease control. The side effect of the oil 
sprays when used to control Sigatoka in Fiji was that it 
created conditions for black leaf streak which was found 
to be an even more serious disease (Firman, 1970). The 
aerial applications of these oil and fungicide and a 
greater freguency of application were needed, compared 
with Sigatoka control in Central America. According to 
Firman (1972) and Long (1971) oil water emulsion with 
benomyl gave a better control of the disease than that
containing maneb. Other reports have it that, prior to
the emergence of black Sigatoka, yellow Sigatoka disease 
was controlled in Fiji by the use of oil sprays but for 
black Sigatoka, combinations of fungicides plus oil, for 
example, manozeb, and benlate were necessary for
effective control (Firman and Hoskin, 1970; Firman, 
1972). The standard recommendation for the Pacific 
Islands was either benlate plus oil or dithane M45 or 
manzate 200 plus oil (Firman, 1976).
Stover and Simmonds (1987) reported that when 
benlate was used almost exclusively throughout the 
Pacific Islands during the 1970s, control was at best 
marginal. The poor levels of control obtained drew 
concern over the possibility of the development of 
strains resistant to benomyl and prompted a re­
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examination of chemicals for Sigatoka control.
The discovery of the effectiveness of petroleum oil 
(alone or with added chemical compounds) was made in the 
French West Indies in control studies on Sigatoka 
(Cuille, 1965). The action of oils in plant disease 
control, mostly arising from work on sigatoka disease, 
was reviewed by Calpouzos (1966). According to him, oil 
reduces spore germination, germ tube growth and 
appresorial formation and thus inhibit host tissue 
penetration. Pont (1970) reported that control was given 
by oil alone in water emulsions with mancozeb or maneb. 
Stover (1968) and Garry (1973), also reported that 
benomyl in such emulsion was effective.
Results from an experiment conducted during 1986 - 
1988 at Fermenta Plant Protection Company Research farm 
in Honduras suggested that good disease control could be 
achieved using chlorothalonil. Slabaugh (1990) confirmed 
that black sigatoka disease could be reduced using 
chlorothalonil when a range of chemicals were evaluated 
in a series of trials in 1977 at Totokoitu Research 
Station, Rarotonga, Cook Islands. It was reported that 
chlorothalonil was particularly effective and convenient 
chemical to use (ie no oil was applied), but it caused 
severe eye irritation.
Another problem encountered with the application of 
fungicides was the development of resistant strains of
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the fungus. Fullerton and Tracy (1984) reported that 
strains of M. fijiensis, resistant to benzimidazoles, 
were first detected in Western Samoa in 1979 and in Tonga 
in 1983. Benlate was withdrawn from use in Western Samoa 
in 1981 and in Tonga in 1985 due to resistant strain 
development. Stover (1977; 1979) reported that in Central 
America, resistant pathogen population decreased rapidly 
after benlate was withdrawn but in Western Samoa, the 
population remained relatively large in most localities. 
Resistant strains were detected in abandoned plantations 
where no sprays were applied for many years.
To solve this problem of fungi developing 
resistance to fungicide, Costa Rica and Honduras reduced 
drastically the use of fungicide cycles applied per year 
by implementing four (4) principal strategies. These 
were:
(1) monitoring the epidemiology of the disease through 
an adapted early warning disease survey.
(2) the use of systemic fungicide, propiconazole, 
integrated with other fungicides.
(3) low volume application techniques with good 
coverage and recovery to obtain miximum efficiency 
and,
(4) change from overhead to under canopy irrigation 
which reduced disease incidence and severity 
(Wielemaker, 1990).
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In Ghana, Twumasi et al (1993) reported that bavistin, 
benlate, dithane M45 and polyram-DF were screen tested by 
foliar spraying and soil application methods, using 
different concentrations and time freguencies at Assin- 
Fosu in the Central Region. Preliminary reports indicate 
that bi-weekly spraying appeared to be more effective 
than monthly spraying. Also bavistin gave a better result 
in controlling the disease than any other fungicide. 
Polyram-DF was also reported to be promising.
2.5 Propiconazole
In the 1980s a new class of fungicides, the 
ergosterol biosynthesis inhibitors, came into widespread 
use. Among them was propiconazole. It is manufactured by 
CIBA-GEIGY under the trade name TILT. According to the 
manufacturers Tilt 250 EC is a broad spectrum foliar 
fungicide with systemic properties for the control of 
powdery mildew, rust and leaf spot diseases in cereals, 
plantain, banana and other crops. The active ingredient 
content is 250g propiconazole per litre. It has the 
chemical formula l-{2-{2,4-dichlorophenyl-4-propyl-l,3- 
dioxolan-zyl-methyl}-lH-l,2,4-triazole. It absorbed by 
assimilating parts of the plant within one hour. It is 
transported acropetally in the xylem. Propiconazole acts 
on the fungal pathogen inside the plant at the stage of 
first haustria formation. It stops the development of
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fungi by interfering with biosynthesis of sterols in cell 
membrane and belongs to the group of DMI-fungicides (ie 
demethylation inhibitors). Although the biological mode 
of action of propiconazole permits protective, curative 
or eradicative use, best results are achieved if the 
product is applied when the disease is active but in the 
early stages of development. Its performance is, however, 
influenced by such factors as weather and plant type 
resistance.
Wielemaker (1988) reported that propiconazole was 
the only triazole compound approved by Costa Rica 
Environmental Protection Agency (EPA) for foliar sprays 
on banana. Propiconazole was the first fungicide used to 
control black leaf streak and listed by the Environmental 
Protection Agency in the United States in 1984 for use on 
banana (Stover, 1993). The use of triazole fungicides, 
however, showed that pathogens displayed increasing 
resistance to these products. The Fungicide Resistance 
Action Committee (FRAC) reported that there was a 
decrease in sensitivity of M. fijiensis to Tilt from 1988 
to 1992.
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CHAPTER THREE
MATERIALS AND METHODS
3.1 Field work
3.1.1 Project site
The research was carried out at the University of 
Ghana Agriculture Research Station, Kade from September 
1995 to April 1997. The mean annual rainfall recorded at 
the station is 1,386.3mm, with the highest rainfall being 
recorded in June/July or September while the lowest 
occured in December. The minimum temperature ranges from 
15.3°C to 24.2°C with the maximum ranging from 28.5°C to 
33.7°C. The wind force on Beaufort scale is from 0 to 4, 
that is, mean speed of between 0 to 13 knots but it is 
between 5-9 knots for the greater part of the year.
3.1.2 Land preparation and treatments
Being a secondary forest, the dominant weed was 
Chromolaena odorata. Therefore the land was prepared by 
slashing without burning. Lining and pegging were carried 
out using the 50m tape measure and pegs. The size of 
each plot was 18 x 10 m2.
The planting distance within a plot was 3m x 2m, and 
the distance between individual plots was 6m. Planting 
holes of 10 x 10 x 30cm3 were dug, using the chisel.
The randomised complete block design (RCBD) was 
used. There were four treatments namely; Tilt (0.125g
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ai/L), Pruning, Tilt (0.125g ai/L) + Pruning and Control 
(neither chemical nor pruning). There were 20 plants per 
plot but records were taken on 15 selected at random. 
Each treatment was replicated 4 times. Analysis of 
variance (ANOVA) procedure based on plot means (Kwanchi- 
Gomez and Gomez, 1984) was carried out for data analysis 
and Least Significant Difference (LSD) test at 0.05 
significance level was used to compare treatment means 
for each parameter.
3.1.3 Planting Material and Planting
The plantain cultivar used was "Brodeyuo" (Dark 
pseudostem) which belongs to the False horn (Apentu) AAB 
group. The split corm technigue (Wilson et al, 1985) was 
used to raise suckers at the nursery for four months. 
They were uprooted, using the chisel and cutlass, and cut 
to an average height of about 50cm. Trimming of roots and 
necrotic lesions were done. Three days after uprooting, 
the suckers were planted on the field. Dead suckers were 
replaced.
3.1.4 Research activities and records taken
Plant height was recorded using a graduated pole 
eight weeks after transplanting and subseguently at 4- 
weekly intervals. Also, the number of expanded non­
drooping leaves were counted starting from the topmost.
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The disease severity on the leaves were scored using a 6— 
grade scale from 0-5 (modified after Gauhl et al, 1993) 
as follows:
0 —  no symptom,
1 —  less than 1% total leaf area attacked (only streaks
and/or up to 10 spots,
2 —  1 to 5% total leaf area attacked,
3 —  6 to 15%
4 —  16 to 33% and
5 —  34 to 100%
From this, percentage total leaf area per plant attacked 
by the fungus was estimated using the formula by Gauhl et 
al (1993) as:
Total leaf area attacked (%) =
LN1 X 1 + LN2 x 5 + LN3 X 15 + LN4 X 33 + LN5 X 100
LN
where LN1 to LN5 = number of leaves with respective 
grades and LN = total number of leaves.
In addition to the severity determination, the 
youngest leaf with symptom (YLWS), which gives an idea of 
how healthy the plant appears (Stover and Dickson, 1970; 
Stover, 1971) was determined. This was done by recording 
the number of the youngest leaf of each test plant to
have the symptoms counting from the folded leaf
downwards. The average of the numbers was calculated for 
each treatment.
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Application of the four treatments were also done 
when the plants were eight weeks old after transplanting 
and subsequently at four weekly intervals until the 
plants were 44 weeks old,when they started flowering and 
no new leaves were coming.The application was done 
immediately after the severity determination. The 
rational for the sequence was to know the initial natural 
infection and also the effect of the previous treatments 
on disease severity. The details of the four treatment 
application were as follows:
a) Pruning - diseased leaves above grade 2 of disease 
development were removed with cutlass from the 
test plants. The prunned leaves were gathered 
outside the field, allowed to wither for 3 days 
and then burnt.
b) Fungicide application - 5ml of Tilt 250 EC (ai 250 
propiconazole per litre) was mixed with 10 litres 
of water to give a concentration of 0.125g ai/L. 
This was sprayed onto both surfaces of the leav 
Spraying was first done with Knapsack sprayer 
(Fig. 1) and later with motorized sprayer 
(Fig. 2) .
c) Tilt + Pruning - diseased leaves above grade 2 
disease development were first prunned and burnt 
in (a) above. Tilt 250 EC was then applied as in 
(b) above.
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Fid. 1: Using knapsack sprayer to spray short plantain
plants with Tilt 250EC.
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Fig. 2 Using motorised mist blower to spray tall 
plantain plants with Tilt 250EC.
Note the diseased lower leaves (arrowed).
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d) control - neither Tilt application nor pruning was 
done.
Harvesting started when the plants were 54 weeks and 
repeated every 2 weeks thereafter. A bunch was considered 
mature when a finger had cracked or was beginning to 
ripen. The experiment was terminated after the 7“ 
successive harvest when the plants were 66 weeks old. At 
harvest, the number of bunches per treatment and bunch 
weight (taken by cutting the peduncle above the first
hand at the scar of the last bract and below the last
hand) were recorded.
However, other components of yield namely, number of 
hands per bunch, number of fingers (fruits) per bunch and 
the circumference, length and weight of the middle finger 
(most of each hand) were also recorded.
3.2 Bioassay Studies in the laboratory
3.2.1 Media Preparation
1.5% water agar (WA) and potato dextrose agar (PDA) 
were separately prepared by autoclaving at a pressure of 
15 lbs psi (1.05Kg/cm2) and a temperature of 121 °C (250F) 
for 15 minutes.
One ml of each of the following concentrations of 
Tilt 250 EC were put into separate Petri dishes. These 
were 0.0125g ai/L, 0.025g ai/L, 0.05g ai/L, 0.0625g ai/L 
and 0.075g ai/L. Ten ml of molten water agar or PDA were
22
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added to form Tilt-ammended media. These were allowed to 
set. Each plate represented a treatment and each 
treatment was repeated four times. There were media which 
did not contain Tilt 250 EC and therefore served as 
control.
3.2.2 Isolation of pathogen
Dried and fresh leaf samples showing advance lesions 
of black Sigatoka (ie necrotic areas characterized by 
greyish spots, a typical symptom of ascospore-bearing 
tissue) were collected from the field at the University 
of Ghana Agriculture Research Station, Kade. A composite 
sample from several plants were collected. These were 
air-dried at room temperature for 24 hours. Isolations 
were done using the ascospore discharged technique 
described by Stover (1980). Leaf sections about 2x2 cm2 
were stapled to a 9cm-diameter filter papers. These were 
immersed in sterile distilled water for 5 minutes and 
then placed in the lids of Petri dishes with the lower 
leaf surface of the leaf section directly above the Tilt- 
ammended water agar. The plates were examined every 15 
minutes for 3 hours for release of ascospores. The 
released ascospores were transferred to a corresponding 
concentration of Tilt-ammended PDA. The plates were 
periodically examined for contamination and pure cultures 
transferred onto fresh Tilt-ammended PDA. The cultures
23
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were incubated at room temperature (27-29 C) under 
continuous light.
3.2.3 Data Collected
Each plate was divided into four sections for 
counting and measurement of ejected ascospores and also 
for measuring the length of germ tube. The parameters 
studied were time for germination after ejection onto 
media, type of germ tube growth, length of germ tube 12 
and 24 hours after ejection and other characteristics of 
the cultures like colour of the culture.
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CHAPTER FOUR
RESULTS
4.1 Field Work
4.1.1 Effect of the treatments on Plant height of 
Plantain
Plant height increased steadily from planting to 
flowering (Fig. 3). The average height at 8 weeks after 
transplanting for Tilt treated plants (TP) was 33.4cm. 
Control plants (CP) recorded the highest figure of 35.8cm 
and the prunned plants (PP) 30.6cm. TP and PP recorded 
values of 36.0cm and 39.8cm each in the 12th and 16th 
weeks respectively. However, from the 32nd week to 
flowering, TP gave the lowest values 92.6cm in the 32nd 
week and 180.1cm at flowering. CP maintained the highest 
value throughout the experimental period reaching an
average height of 226.7cm at flowering. Tilt + Prunning
treated plants (TPP) followed with 220.9cm. The average 
height at flowering for PP and TPP were 222.1cm and 
228.0cm respectively.
4.1.2 Effect of Tilt and Pruning on Average number of
leaves of plantain infected by black Sigatoka
The average number of leaves for TP, PP, TPP and CP in 
the 8th week 4.7, 4.4, 4.3 and 4.0, respectively (Table 
1). In the 16th week, TP recorded the highest value of
5.8 and maintained this position till flowering, ending
25
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H
ei
gh
t 
(c
m
)
Fig. 3 Plant height of plantain infected by Black Sigatoka.
-T ilt (TP) —A— Pruning (PP) —o— Tilt+Pruning (TPP) —X— Control (CP)
Weeks after planting
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Table 1: Average number of leaves of plantain infected by black Sigatoka from week 8 to week 44.
Treatment W e e k s
8 12 16 20 24 28 32 36 40 44
Tilt (TP) 4.7 5.0 5.8 7.1 7.8 8.2 11.8 12.6 14.6 16.6
Pruning (PP) 4.1 4.6 5.0 5.7 6.0 7.1 9.9 9.7 11.7 13.6
Tilt+Pruning (TPP) 4.3 4.6 5.1 5.8 6.2 7.2 11.0 11.4 13.0 14.5
Control (CP) 3.6 4.7 5.0 6.1 6.2 6.9 7.6 8.4 12.1 13.8
LSD (0.05) NS NS NS NS NS NS 1.22 2.72 1.69 1.99
NS = Not significant
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with 16.6. In the 16th, 20th and 24th weeks, PP 
recorded the lowest values of 5.0, 5.7 and 6.0
respectively. CP which had the second highest values in 
the 20th and 24th weeks recorded the lowest values of 6.9,
7.6 and 8.4 in the 28th, 32nd and 36th weeks respectively. 
In the 40th week, the number of leaves for CP was 12.1 
which was higher than the value for PP. The number of 
leaves in 44th week were 16.6, 13.6, 14.5 and 13.8 for 
TP, PP, TPP and CP respectively.
4.1.3 Effect of Tilt, Pruning and amount of rainfall on 
severity of black Sigatoka 
The disease was observed when the plants were 8 weeks 
old. Disease severity, however, fluctuated from the 
beginning to the end of the experiment and followed the 
same trend in all the treatments (Fig. 4). From the 8th 
to 44th week, CP were the most diseased. Throughout the 
experimental period,the total leaf area attacked in the 
CP was higher than 13% while it was between 2% to 6.4% 
for the rest of the treatments.
When the plants were 16 weeks old, the disease 
severity was higher in CP than the other three treatments 
(Fig. 5). In week 24, the disease could again be seen 
more in CP than TP, PP and TPP (Fig.6). In all the 
treatments, the highest severity was observed when the 
plants were 32 weeks old and this coincided with the peak
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Fig.4 Effects of Tilt, Pruning and amount of Rainfall on Black
Sigatoka.
Tilt (TP) - a - Pruning (PP)
Tilt+Pruning (TPP) —X— Control (CP)
-Rainfall, (mm)___________ _ ____ _______________
Weeks after planting
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Fig. 5: Effect of Tilt and Pruning on black Sigatoka
disease severity of 16-week-old plantain plants 
at Kade.
A = Plants sprayed with Tilt.
B = Plants for pruning treatment (diseased leaves yet1' 
to be prunned),
C = Previously prunned plants and sprayed with 
Tilt.
D = Control plant (neither prunned nor Tilt),
Note the diseased leaves especially the 
second plant.
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A = Plants sprayed with Tilt.
B = Plants prunned only.
C = Plants prunned and sprayed with Tilt.
D = Control plants (neither pruning nor Tilt).
Note most of diseased leaves hanging.
Fig. 6: Effect of Tilt and Pruning on black Sigatoka disease
severity of 24-week-old plantain plants at Kade.
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of the rainfall (295mm) in Kade area where the experiment 
was conducted (Figs. 4 and 7). The lowest severity was 
recorded at week 28 for TP and TPP.
The youngest leaf with symptom (YLWS) also 
fluctuated throughout the period as seen in (Fig. 8). 
Eight weeks after transplanting, TP and PP had the same 
value of 2.6, while TPP recorded 2.2 and CP 2.3. The 
highest values of 6.8, 5.0, 5.9 and 3.4 for TP, PP, TPP 
and CP respectively, were recorded in week 36. These 
decreased to 5.8, 4.2 and 5.0 for TP, PP and TPP
respectively by the 44th week. while CP maintained a 
constant value of 3.4.
The results meant that at the 44th week after 
transplanting, on the average, the youngest leaf to have 
the symptom was 6th leaf for TP while it was 4th, 5“ and 
3rd for PP, TPP and CP respectively. It meant that the 
plants treated with Tilt appeared healthier than the 
control.
4.1.4 Effect of Tilt and Pruning on yield of plantain:
The data on the yield of plantain harvested between 
week 54 and 66 are presented in Fig. 9 and Table 2. 
Maturity delayed in the control plants. Thus by the 54th 
week while 4 and 2 bunches were harvested for TP and TPP 
respectively, nothing was harvested in either CP or PP. 
Also, by 56th week, only 2 and 3 bunches were harvested
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A = Plantif ^sprayed wi^h Tilt showing visible symptom 
black j§"igatoka. : *, I
\ " \ / £■ r
B = Plants',prtinned^ only showing no visible symptom.
C = Plants prunned and sprayed with Tilt showing no 
visible symptom.
D = Control plants (neither pruning nor Tilt) with the 
lower and hanging leaves showing advanced stages of 
black Sigatoka.
Fia. 7: Effect of Tilt and Pruning on black Sigatoka disease
severity of 32-week-old plantain plants at Kade.
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33
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Yo
un
ge
st
 
le
af
 w
ith
 
sy
m
pt
om
 
(Y
LW
S
)
Fig. 8 Effects of T ilt and Pruning on youngest lea f to show symptoms  
(YLWS) of B lack S igatoka.
!—O— Tilt (TP) Pruning (PP) —o— Tilt+Pruning (TPP) — X —  Control (CP)
24 28
W eeks after planting
34
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N
um
be
r 
of 
bu
nc
he
s 
ha
rv
es
te
d
Fig. 9 Number of bunches harvested from week 54 to week 66
Tilt (TP) Pruning (PP) — Tilt+Pruning (TPP) -X -C o n tro l (CP)
16 T"
weeks after planting
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Table 2; Yield and components of yield 66 weeks after transplanting.
Treatments Total Total Bunch No. of No. of Middle finaer
no. of 
bunches
bunch
weight
(Kg)
weight
(Kg/plant)
hands/
bunch
fruits/
bunch
circumf. 
(cm)
Length
(cm)
weight
(cm)
Tilt (TP) 54 453.0 8.4 6.4 26.4 12.9 25.3 0.258
Pruning (PP) 52 392.2 7.5 6.1 25.6 12.5 24.2 0.258
Tilt+Pruning(TPP) 50 405.0 8.1 6.3 26.1 12.6 24.8 0.253
Control (CP) 47 249.1 5.4 5.8 25.4 12.1 23.6 0.186
LSD CD. 05) NS NS 0.93 NS NS NS NS 0.05
NS = Not significant.
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for CP and PP respectively, while 7 bunches each were 
harvested for TP and TPP.
By the 60th week, while 13, 11 and 9 bunches were 
harvested in TP, TPP and PP respectively, only 6 bunches 
were harvested in the CP. By the 62nd week when the PP 
reached its peak of 14 bunches, CP had 12, TP 11 and TPP 
8 .
At 64"“ week, CP reached its peak of 15 bunches 
harvested while 13, 7 and 5 bunches were harvested from 
PP, TPP and TP respectively. At the 66to week, there was 
a fall of harvest in all the treatments. These were 8, 6, 
5 and 2 bunches in CP, PP, TPP and TP respectively. In 
all, the total number of bunches harvested were 54, 52, 
50 and 47 for TP, PP, TPP and CP respectively (Table 
2).There was no significant difference in the number of 
bunches in the four treatments. However, the total 
weights of 435Kg, 392.2Kg, 405Kg and 249.lKg in TP, PP, 
TPP and control showed significant difference between CP 
and the other treatments. The difference was not due to 
number of hands per bunch or number of fruits per bunch 
or the circumference or length of the middle finger. It 
was rather due to the weight of the fingers. On the 
average, there were 6.1 hands for PP, 6.4 for TP, 6.3 for 
TPP and 5.8 for CP. The number of fingers per bunch were 
26.4, 25.6, 26.1 and 25.4 for TP, PP, TPP and CP
respectively. The circumference of the middle finger
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ranged from 12.1cm to 12.9cm, while its length ranged 
from 23.6cm to 25.3 cm in all the treatments.
4.2. Bioassay in the laboratory for testing efficacy of 
the Chemical (Tilt)
4.2.1 Ascospore Discharge
It was observed that the discharge of ascospores 
from the diseased leaves onto the media started 15 
minutes after the leaf segments were put in the lids of 
Petri dishes as described earlier. One hour later, the 
discharge was completed. The ascospores released were not 
different from one another (Fig.10). They were hyaline, 
2-celled with one cell bigger than the other with a 
slight constriction at the septum. The sizes ranged from 
13.8-19.6um x 3.3-3.Sum.
4.2.2 Ascospore germination
Germination started in all cases about 12 hours 
later (Figs. 11, 12, 13 and 14). However, it could be 
seen from Table 3 that there was 100% germination for the 
Control plate. The plates with Tilt concentrations of 
0.0625g ai/L and 0,075g ai/L recorded the lowest values 
of 16% and 5% respectively. This trend was again observed 
24 hours later. It was also observed that germination was 
either unipolar or bipolar, depending on the
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Fig. 10: Ascospores of Mycosphaerella fijiensis
(arrowed) discharged from diseased plantain 
leaves on PDA (x 125).
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Fig. 11; Germinating ascospores of Mycosphaerella 
fijiensis of plantain on PDA (x 250).
Note the arrowed constriction at the septum.
Fig. 12: Germinating ascospores of Mycosphaerella
fijiensis of plantain on 0.0125g ai/L Tilt- 
ammended PDA 12 hours after discharge onto PDA 
(x 125).
Note: Some are unipolar and others bipolar as 
shown by arrows.
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Fia. 13; Germinating ascospores of Mycosphaerella 
fijiensis of plantain on 0.05g ai/L Tilt- 
ammended PDA 12 hours after discharge.
Note: Some are unipolar, others bipolar and the 
rest with no germ tube as shown by arrows.
Fig. 14: Germinating ascospores of Mycosphaerella
fijiensis of plantain on PDA 12 hours after 
discharged (x 125).
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Table 3: Percentage germination of M. fijiensis ascospores
discharged from diseased plantain leaves on different 
concentration of Tilt-ammended PDA.
Treatment __________________Germination______________________
after 12 hours after 24 hours at both ends
Control 100 100 100
0.0125g ai/L 85 92 85
0.025g ai/L 67 70 80
0.05g ai/L 48 57 48
0.0625g ai/L 16 24 17
0.075g ai/ L 5 13
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concentration of Tilt in the Tilt-ammended medium. Germ 
tubes were straight to slightly curved.
No measurement could be taken 24 hours after 
germination for the control plate and the plate with
0.0125g ai/L Tilt (Table 4) . This was because the mycelia 
grew faster and interwoven, making it impossible to trace 
individual mycelia from one end to the other (Fig. 15).
4.2.3 Culture Characteristics
No visible growth was observed with the naked eye 
until after 4 days. The culture on the control plate was 
compact with whitish aerial mycelia. The underside was, 
however, dark (Fig. 16). The culture on the plate with
0.0125g ai/L Tilt had grey velvety surface with a black 
underside (Fig. 17).
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discharged from diseased plantain leaves (urn).
Table 4: Average length of germ tube of H. fijiensis ascospores
Treatments 12 hours 24 hours
Control 160.0 Over grown*
0.0125g ai/L 146.0 Over grown*
0,025g ai/L 90.0 91.0
0.05g ai/L 77.0 85.0
0.0625g ai/L 52.0 53.0
0.075g ai/L 43.0 43.0
* Not possible to measure since mycelia were interwoven.
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Fia. 15: Germinating ascospores of Mycosphaerella
fijiensis of plantain on PDA 24 hours after 
discharged (x 125).
Note: The mycelia grew faster and interwoven, 
making it impossible to trace individual 
mycelia from one end to the other.
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Fia. 16! Cultures of Mycosphaerella fijiensis from
diseased plantain leaves on PDA.
A = 2-week-old culture with whitish aerial 
mycelia.
B = 2-week-old culture with reverse (underside) 
of mycelia black.
C = 4-week-old culture with whitish aerial 
mycelia.
D = 4-week-old culture with reverse (underside) 
of mycelia black.
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B
Fig. 17: Cultures of Mycosphaerella fijiensis from
diseased plantain leaves on 0.0125g ai/L Tilt- 
ammended PDA.
Note: Greyish aerial mycelia (A) and reverse 
(underside) black (B).
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CHAPTER FIVE
DISCUSSIONS
5.1 Effect of Tilt and Pruning on height of plantain
Statistically, there was no difference between the 
average height values recorded for the four treatments 
from transplanting to the 28“ week. This shows that 
neither the disease nor the Tilt and/or Pruning had any 
effect on the height of the cultivar used in the 
experiment which is said to be on the average about 180cm 
tall at flowering (Nsiah, personal communication).
From week 8 to week 24, there was no difference in 
the average number of leaves recorded for all the 
treatments. However, significant differences were noticed 
from week 32 to week 44. The differences might be due to 
the black Sigatoka disease which causes the leaves to dry 
out faster than they otherwise would have done. According 
to Mwashayenyi (1994), the higher the number of leaves on 
banana, the heavier the fruit bunch. This, he said, may 
be linked with dry matter accumulation pattern of the 
plant, suggesting that plants with larger number of 
leaves also have higher photosynthetic ability which 
reflects in heavier bunch weight. He further stated that 
at least, 8 leaves were required to sustain a bunch. The 
lowest average number of leaves recorded at the time of 
flowering (week 44) was 13.6 for plant prunned (PP). It 
could be said that all the plants in the experiment could
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sustain a bunch. However since the number included 
diseased leaves at different stages of disease 
development their photosynthetic ability will not be the 
same. This difference might account for the difference in 
bunch weight at harvest.
5.2 Effect of Tilt, Pruning and amount of rainfall on 
severity of black Sigatoka and yield of plantain at 
Kade
The percentage total area attacked on the Control plant 
was significantly different from the other three 
treatments which were not significantly different from 
each other at 5% significance level. This means that 
chemical treatment by Tilt or cultural practices like 
pruning could significantly reduce the severity of the 
disease. Among the three treatments, however, severity 
was as follows: plants prunned (PP) was the highest, 
followed by Tilt treated plants (TT) and Tilt + Pruning 
treated plants (TPP) in that order. On the average, 
severity was 16% of the total leaf area for Control 
plants (CP) while it was 4.6%, 5.1% and 3.8% for TP, PP 
and TPP respectively. The disease was severe in the CP 
while it was rare to mild in the other treatments when 
the modified scale of Gauhl et al (1993) is used.
The fluctuation of disease severity observed
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generally followed the rainfall pattern at Kade area 
during the research period. The highest severity was 
observed in week 32 when the average monthly rainfall was 
at its peak of 295mm. This confirms earlier report by 
Jacome et al (1991) that severity of black Sigatoka 
generally increases with increasing rainfall. The 
ascospores of M. fijiensis which cause considerable 
infection require free water or nearly saturated 
environment (RH=98 - 100%) for germination and germ tube 
growth (Jacome and Schuh, 1992).
The differences noticed in the youngest leaf with 
symptom (YLWS) values between CP and the other three 
treatments from week 28 to week 44 were significant at 
5%. One characteristic of the disease is that older 
leaves become more diseased than younger ones. Thus if 
the plantain has 10 leaves and the youngest leaf to have 
the disease is 6, it means the first five younger leaves 
will be free from the disease while only the remaining 
older five leaves will have the disease with increasing 
severity from the 6“ to the 10th. On the other hand, if 
the youngest leaf to have the disease is 3, it means only 
two leaves will be clean while the remaining eight older 
leaves will be diseased and the plant will look more 
diseased than the previous one. In this experiment, the 
control plants (CP) had YLWS of 3 while Tilt treated 
plants (TP) had 6 indicating that the control looked more
50
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diseased.
When harvesting started 54 weeks after 
transplanting, no bunch was harvested from either PP or 
CP. By 62nd week, 50% of bunches have been harvested for 
the CP, while 65%, 76% and 87% bunches have been
harvested for PP, TPP and TP respectively. The results 
indicate that black Sigatoka could delay the maturity of 
plantain. When the harvesting was stopped at the 66th 
week after transplanting there was no significant 
difference between the number of bunches in the control 
and the other treatments. However, the bunch weight 
recorded for CP was significantly lower than the weights 
recorded for the other three treatments. The differences 
in bunch weights were due to significant differences in 
weight per finger (ie individual fruit weight) which were
0.258Kg, 0.245Kg, 0.253Kg and 0.186Kg for TP, PP, TPP and 
CP respectively. This is in line with observation by 
Baiyeri and Mbah (1994), that bunch weight correlates 
with finger weight but weakly correlate with finger 
number. There was no significant difference in the number 
of hands per bunch. Also the number of fingers per bunch 
were not significantly different from each other.
Correlation analysis indicated a negative but 
significant association (r = 0.96) between severity of 
black Sigatoka disease and yield. This implies that as 
disease severity increases yield is reduced. The
51
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differences in yield between the CP and the other 
treatments are 203.9Kg (45.0%) for TP, 143.1 Kg (36.5%) 
for PP and 155.9Kg (38.5%) for TPP. These agree with what 
Stover (1983) and Mobambo et al (1993) said that plantain 
yield loss up to 50% could be recorded in the first 
cropping cycle. Both delay in maturity and reduction in 
yield weight of fingers because of the disease may be due 
to its adverse effect on the photosynthetic efficiency of 
the plant.
5.3 Efficacy of Tilt as evidence in Bioassay studies: 
The ascospore morphology observed conformed to the 
description of M. fijiensis by Mulder and Holliday 
(1974). The ascospores that were ejected from the 
diseased plantain leaves were therefore of M. fijiensis. 
However, germination started about 12 hours after 
discharge, instead of the 24 hours reported by Mulder and 
Holliday (1974). That no visible colony was observed with 
the naked eye until after 4 days confirmed what Natural 
(1990) said that colonies from single spore isolates on 
artificial media grows very slowly and become visible 4-6 
days after incubation on PDA at 22-25°C under continuous 
light. The whitish aerial mycelia with reverse (under) 
side dark for the control (only PDA) plate is in line 
with what Mulder and Holliday (1974) observed. In the
52
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case of 0.0125g ai/L Tilt-ammended PDA, these aerial 
mycelia later turned olivaceous gray. The colonies were 
compact, raised with non-circular margin. Natural (1974) 
said this is possible if there is toxin in the culture. 
There was no appreciable growth in the other Tilt - 
ammended PDA plates. Tilt concentration of 0.075g ai/L 
and above in a medium can therefore stop the growth of M. 
fijiensis since it was this concentration that had only 
5% of ascospores germination 12 hours after discharge and 
7% germination 24 hours after discharge.
53
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CHAPTER SIX
CONCLUSIONS AND RECOMMENDATIONS
From the above data, it could be said that
i. black Sigatoka could delay maturity of plantain 
and reduce bunch weight.
ii. pruning and burning of infected leaves was 
effective in the control of black Sigatoka 
disease.
Farmers should be encouraged to use it as an alternative 
to chemical control which is expensive and 
environmentally unfriendly, and therefore cannot be 
sustained by the peasant farmers in Ghana.
The following recommendations could be made:
1. the experiment should be repeated.
2. different cultivars of plantain should be used.
3. the land area used should be increased.
4. the experiment should be multilocational.
5. two or more fungicides should be used and
6. the experiment should be extended into the second 
cropping season.
54
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CHAPTER SEVEN
LITERATURE CITED
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13. Foure, E. 1985. Les cercosporioses du bananier et
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to evaluate host resistance to black Sigatoka. 
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40. Pasberg-Gauhl, C. 1989. Untersuchungen zur
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41. Pasberg-Gauhl, C. 1994. Symptom development of
black Sigatoka leaf spot on young or adult banana 
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North Queensland Aust. J. Exp. Agric. 27:919-923.
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63. stover, R. H. and Simmonds, N. W. 1987. Bananas.
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73* Wielemaker, F. 1988. Leaf emission rate
determination in Rio Frio, Costa Rica. Internal 
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Montpellier, France.
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Aj 28 wepks_____________________________________ ____________________
APPENDIX i- ANOVA table for average number of leaves 28, 32, 36 &
44 weeks after planting.
Source of 
variation
Degree of 
freedom
Sum of squares Mean square Fcal
Treatment 3 4.69 1.56 1.48
Block 3 2.93 0.98 0.92
Error 9 9.54 1.06
Total 15 17.1
B. 32 weeks
Source of Degree of Sum of squares Mean square Fcal
variation freedom
Treatment 3 40.19 13.40 47.52**
Block 3 1.63 0.54 1.92
Error 9 2.53 0.28
Total 15 44.36
C. 36 weeks
Source of Degree of Sum of squares Mean square Fcal
variation freedom
Treatment 3 40.15 13.38 9.53**
Block 3 4.31 1.44 1.02
Error 9 12.64 1.40
Total 15 57.10
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D. 40 weeks
Source of 
variation
Degree of 
freedom
Sum of squares Mean square Fcal
Treatment 3 20.49 6.83 6.14*
Block 3 3.40 1.13 1.02
Error 9 10.01 1.11
Total 15 33 .89
E. 44 weeks
Source of Degree of Sum of squares Mean square Fcal
variation freedom
Treatment 3 21.85 7.28 4.70*
Block 3 6.83 2.20 1.42
Error 9 13.40 1.55
Total 15 42.40
APPENDIX II
A. 28 weeks
ANOVA table for Youngest Leaf with Symptom (YLWS) 28, 
32, 36, 40 and 44 weeks after planting.
Source of Degree of Sum of squares Mean square Fcal
variation freedom
Treatment 3 7.07 2.36 10.90**
Block 3 0.37 0.12 0.57
Error 9 1.95 0.22
Total 15 9.38
64
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B. 32 weaks
Source of 
variation
Degree of 
freedom
Sum of squares Mean square Fcal
Treatment 3 5.63 1.88 12.97**
Block 3 0.34 0.11 0.79
Error 9 1.30 0.14
Total 15 7.28
C. 36 weeks
Source of 
variation
Degree of 
freedom
Sum of squares Mean square Fcal
Treatment 3 24.02 8.01 42.88**
Block 3 0.17 0.06 0.30
Error 9 1.68 0.19
Total 15 25.87
D. 40 weeks
Source of Degree of Sum of squares Mean square Fcal
variation freedom
Treatment 3 17.83 5.94 42.44
Block 3 0.42 0.14 0.99
Error 9 1.26 0.14
Total 15 12.72
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E. 44 weeks
Source of 
variation
Degree of 
freedom
Sum of squares Mean square Fcal
Treatment 3 10.83 3.61 26.34**
Block 3 0.65 0.22 1.59
Error 9 1.23 0.14
Total 15 12.72
APPENDIX III ANOVA table for average bunch weight.
Source of Degree of Sum of squares Mean square Fcal
variation freedom
Treatment 3 27.27 9.15 13.45**
Block 3 4.47 1.50 2.21
Error 9 6.08 0.68
Total 15 37.82
APPENDIX IV ANOVA table for average number of fingers per bunch
Source of Degree of Sum of squares Mean square Fcal
variation freedom
Treatment 3 33.75 11.25 2.74
Block 3 21.53 7.18 1.75
Error 9 36.92 4.10
Total 15 92.20
66
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APPENnTY v ANOVA table for length of 'middle finger•
Source of 
variation
Degree of 
freedom
Sum of squares Mean square Fcal
Treatment 3 11.57 3.85 1.58
Block 3 11.32 3.77 1.55
Error 9 21.85 2.42
Total 15 44.74
APPENDIX VI ANOVA table for weight of 'middle finger'
Source of Degree of Sum of squares Mean square Fcal
variation freedom
Treatment 3 0.0065 0.0022 1.187*
Block 3 0.0022 0.0007 0.402
Error 9 0.0163 0.0018
Total 15 0.02
APPENDIX VII ANOVA table for disease severity from week 8 - 4 4 .
A. week 8
Source of Degree of Sum of squares Mean square Fcal
variation freedom
Treatment 3 9.925 3.308 109.511*
Block 3 0.096 0.032 1.062
Error 9 0.272 0.032
Total 15
67
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IL—  week 1 2
Source of Degree of Sum of squares Mean square Fcal
variation____ freedom_________________________
Treatment 3 8.400 2.800 33.758
Block 3 0.052 0.017 0.211
Error 9 0.746 0.083
Total 15
C. week 16
Source of 
variation
Degree of 
freedom
Sum of squares Mean square Fcal
Treatment 3 9.940 3.313 92.922
Block 3 0.042 0.014 0.390
Error 9 0.321 0.036
Total__________ 15
D. week 20
Source of 
variation
Degree of 
freedom
Sum of squares Mean square Fcal
Treatment 3 12.442 4.147 67.233
Block 3 0.039 0.013 0.210
Error 9 0.555 0.062
Total 15
68
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E. week 24
Source of Degree of Sum of squares Mean square Fcal 
variation_____freedom_________________________________________
Treatment 3 13.011 4.337 221.621
Block 3 0.092 0.031 1.567
Error 9 0.176 0.20
Total 15
F. week 28
Source of Degree of Sum of squares Mean square Fcal
variation freedom
Treatment 3 17.071 5.690 500.979
Block 3 0.117 0.039 3.430
Error 9 0.102 0.011
Total 15
G. week 32
Source of Degree of Sum of squares Mean square Fcal
variation freedom
Treatment 3 10.103 3.368 271.442
Block 3 0.005 0.002 0.147
Error 9 0.113 0.012
Total 15
69
University of Ghana                              http://ugspace.ug.edu.gh
H. week 3 6
Source of 
variation
Degree of 
freedom
Sum of squares Mean square Fcal
Treatment 3 9.313 3.104 119.750
Block 3 0.092 0.031 1.186
Error 9 0.233 0.026
Total 15
I. week 40
Source of Degree of Sum of squares Mean square Fcal
variation freedom
Treatment 3 11.010 3.670 659.832
Block 3 0.004 0.001 0.253
Error 9 0.050 0.006
Total 15
J. week 44
Source of Degree of Sum of squares Mean square Fcal
variation freedom
Treatment 3 15.918 5.306 276.597
Block 3 0.066 0.022 1.145
Error 9 0.176 0.019
Total 15
70
University of Ghana                              http://ugspace.ug.edu.gh
University of Ghana                              http://ugspace.ug.edu.gh