Browsing by Author "Obeng-Ofori, D."

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Ability of the larval ectoparasitoid Habrobracon hebetor (Say, 1836) (Hymenoptera: Braconidae) to locate the rice moth Corcyra cephalonica (Stainton, 1865) (Lepidoptera: Pyralidae) in bagged and bulk stored rice [Wirtsfindung des larvalparasitoiden habrobracon hebetor (say, 1836) (Hymenoptera: Braconidae) in gesacktem und geschüttetem reis gegenüber der reismotte Corcyra cephalonica (Stainton, 1865) (lepidoptera: Pyralidae)]
(Journal of Plant Diseases and Protection, 2010-04) Adarkwah, C.; Büttner, C.; Reichmuth, C.; Obeng-Ofori, D.; Prozell, S.; Schöller, M.
The potential of using Habrobracon hebetor for the inundative biological control of Corcyra cephalonica in rice stored in jute bags and in bulk was assessed. Host-finding in the situation of bag storage was tested by preparing small jute bags measuring 18 × 16 cm filled with 5 kg of un-infested rice grains. In the first experiment, 60 larvae of C. cephalonica were released into the bag. The bag was placed in an empty climatized room with an area of 12.3 m2. Sixty H. hebetor adults (sex ratio of 1 male: 2 females) were released at a distance of 1.6 m away from the jute bag. The number of H. hebetor adults that entered the jute bag was counted daily for 8 days by opening the bag and counting the parasitoids. Only 3% of the parasitoids entered the jute bag. In a second experiment, 60 C. cephalonica larvae were placed inside a wire gauze cage within the jute bag. Ten H. hebetor adults were released into the jute bag. The bag was sealed. After 1 week the cage was removed, and the number of C. cephalonica as well as F1 generation of H. hebetor that emerged was recorded. H. hebetor was able to significantly reduce the number of C. cephalonica emerging from the bagged rice; the corrected mortality due to the parasitoid release was 92.13%. The emergence of H. hebetor progeny started on day 9 after the introduction of the parasitoids and continued until day 21. Host-finding in the situation of bulk rice was tested in glass cylinders (50 cm height, Ø = 25 cm) containing caged larvae at horizontal depths of 7 and 14 cm. H. hebetor was able to find its host C. cephalonica in both depths; significantly more F1 H. hebetor adults emerged from hosts placed 7 cm deep. The implications of these results with respect to the suitability of H. hebetor for the biological control of C. cephalonica in bagged and bulk rice are discussed. © Eugen Ulmer KG, Stuttgart.
Abundance and distribution of the Mediterranean of the fruit fly Ceratitis capitata (Diptera:Tephritidae), in Late Valencia citrus orchards in Ghana
(International Journal of Tropical Insect Science, 2009) Afreh-Nuamah, K.; Appiah, E.F.; Obeng-Ofori, D.
The abundance and distribution of Ceratitis capitata (Wiedemann) in Late Valencia citrus orchards and other alternative host crops was investigated using trimedlure-baited traps at the University of Ghana's Agricultural Research Centre in the Eastern region of Ghana. The effect of some climatic factors on the population dynamics of the pest was also studied. The population of C. capitata increased from September to October 2006 and from February to March 2007, when Late Valencia citrus fruits were ripening or ripened. The fruit fly population was the lowest from November 2006 to January 2007 when citrus fruits were in the immature green stage. Ceratitis capitata was not trapped in mango, pawpaw and pepper fields and did not emerge from fruits of these crops. Multiple regression analyses also revealed that rainfall and temperature significantly influenced the pest population. The results of this study have important implications on the decision-making process for the safe, effective monitoring and management of C. capitata in Late Valencia citrus orchards in the study area in Ghana and probably in other areas as well.
African weaver ant-produced semiochemicals impact on foraging behaviour and parasitism by the Opiine parasitoid, Fopius arisanus on Bactrocera invadens (Diptera: Tephritidae)
(Biological Control, 2014-12) Appiah, E.F.; Ekesi, S.; Afreh-Nuamah, K.; Obeng-Ofori, D.; Mohamed, S.A.
The fruit fly, Bactrocera invadens is an alien invasive pest of mango in Africa. The predatory African weaver ant, Oecophylla longinoda is being promoted for managing B. invadens and classical biological control with the Opiine parasitoid, Fopius arisanus is also underway. The current study investigated interactions between these two natural enemies. Specifically we assessed whether semiochemicals deposited by the ant on leaves and fruit affected the landing behavior of F. arisanus, its patch residence time and subsequent parasitism rates. Results showed that significantly more F. arisanus landed on 'ant-unexposed' leaves and fruits (leaves: 3.8 ± 0.5-7.7 ± 0.8; fruits: 4.1 ± 0.1-8.1 ± 1.2) compared with 'ant-exposed' leaves and fruits (leaves: 0.4 ± 0.1-2.5 ± 0.3; fruits: 0.2 ± 0.1-2.8 ± 0.7) from mango, citrus, guava and avocado. Parasitoid patch residence times were significantly longer on 'ant-unexposed' mango fruits (654.2 ± 28.4. s-1034.2 ± 112.6. s) compared to 'ant-exposed' fruits (75.2 ± 18.4. s-144.8 ± 42. s) regardless of whether eggs of B. invadens were present. In terms of percent parasitism, F. arisanus achieved significantly higher parasitism rates in B. invadens from 'ant-unexposed' mango fruits (72.8 ± 3.8) compared with 'ant-exposed' fruits (18.2 ± 1.8). Regression analysis showed a significant inverse relationship between the duration of exposure of mango fruits to ant-produced semiochemicals and the number of F. arisanus adults landing on fruits and percent parasitism. In field cages, 32% parasitism of B. invadens was achieved in mango fruits on trees without ants and 11% in mango fruits on ant-infested trees. These results suggest the potential for biotic interference between the two natural enemies if they are recommended for use within the same ecosystem. © 2014 Elsevier Inc.
Assessing the effectiveness of a local agricultural research committee in diffusing sustainable cocoa production practices: The case of capsid control in Ghana
(International Journal of Agricultural Sustainability, 2007-01) Ayenor, G.K.; Röling, N.; Van Huis, A.; Padi, B.; Obeng-Ofori, D.
The conventional method of ‘delivering’ technologies recommended by researchers to farmers through extension has proved ineffective, resulting in a persistent low (3.5% over ten years) adoption of research-based cocoa technologies. The present study was conducted in the Eastern Region of Ghana and assessed the impact of the Local Agricultural Research Committee (LARC) approach on the diffusion of capsid management knowledge and practices, developed with the LARC, to others in the community. Capsids (Sahlbergella singularis and Distantiella theobroma) were diagnosed as the most serious production constraint. LARC members engaged in intensive interactive learning and experimentation to control them. The interactive approach developed by the International Centre for Tropical Agriculture was used to link the LARC with community farmers, a majority of whom aspired to produce organic cocoa for a premium. The LARC acquired vital agro-ecological knowledge on capsid management, including skills in scouting for capsids to determine their temporal distribution and systematic experimentation with control methods, before presenting its results to the community. This article reports on a survey comparing three categories of farmers: LARC members, exposed and non-exposed community farmers, so as to assess the diffusion and impact of LARC knowledge co-production. The results show that the LARC approach significantly influenced acquisition and diffusion of knowledge and practices. © 2007 Taylor & Francis Group, LLC.
Assessment of storability of two maize cultivars in a hermetic triple layer biodegradable bag
(Acta Horticulturae, 2015-02) Ansah, F.A.; Fatunbi, A.O.; Adekunle, A.A.; Obeng-Ofori, D.; Afreh-Nuamah, K.; Anankware, J.P.; Badu, A.S.
Storage of maize is very important for food security, especially in developing countries; like Ghana. However, several abiotic and biotic factors cause considerable losses during its storage. Therefore, the work studied the effectiveness of hermetic triple layer biodegradable bags (HTLBB) and polypropylene interwoven bags (PIB) in reducing losses of stored maize. Experiments were conducted in a small holder farmer storage crib and in a laboratory. A factorial combination of HTLBB, PIB and maize cultivars, improved 'Obatanpa' and local 'Denkye' were used. The samples were stored for six months at an average temperature of 27°C and 58% RH. The moisture content, hidden infestation, weight loss, germination capacity and colour were assessed. A significant increase in the moisture content of both cultivars (12.4-15.4%) was found in HTLBB-stored samples probable due to airtight conditions and the respiratory activities of grains, while in PIB no significant differences were found (12.4-12.9%). Laboratory and field assessment of percentage germination and emergence was higher in 'Obatanpa' than in 'Denkye'. However, HTLBB-stored samples, kept 90% of germination capacity while in PIB-stored, a maximum of 60%. Weight losses were also lower in HTLBB-stored 'Obatanpa' and 'Denkye' at 7.4 and 3.8% than PIB-stored at 15.1 and 9% respectively, attributable to varietal type and hidden infestation. Colour changes were observed in both storage bags which were related to possible increase in carotenoid content during storage. As main conclusion, HTLBB has the potential to protect stored maize better than PIB without any chemical treatment; provided its moisture content is very low.
Assessment of the Damage Caused by Corcyra Cephalonica (Stainton) (Lepidoptera: Pyralidae) and Araecerus Fasciculatus (Degeer) (Coleoptera: Anthribidae) to Stored Cocoa Beans in Ghana
(University of Ghana, 1999-02) Azalekor, W.; Obeng-Ofori, D.; Wilson, D.; University of Ghana, College of Basic and Applied Sciences, School of Agriculture, Department of Animal Science
The damage caused by Corcyra cephalonic a and Araecenus fasciculatus to cocoa beans was studied at the Research Department of Quality Control Division of COCOBOD, Tema. The study included breeding of the two insects on cocoa beans to investigate the biology, fecundity and progeny production of the two insect species. The free fatty acid level of cocoa beans was also determined and the change in this level due to insect damage was calculated with respect to undamaged ones. The contaminants produced by these insects were also determined. Araecerus. fasciculatus did not breed on cocoa beans but C. cephalonica bred well on cocoa beans. Ten C. cephalonica larvae produced 608 adults after four months storage. C. cephalotiica bred better on crushed cocoa than whole cocoa beans. Developmental period of 33.8 days was recorded on crushed cocoa beans while 37.9 days were recorded on whole cocoa beans. Fecundity o f C. cephalonica was also higher on crushed cocoa beans compared to whole cocoa beans, laying 174 and 141 eggs, respectively. There was significant difference between the survival and establishment o f C. cephalonica and A. fasciculatus and hence the damage caused. C. cephalonica produced the highest quantity of contaminants of 77.2 g when alone and 67.8 g when introduced with A. fasciculatus. The highest percentage seed damage and weight loss of 46.7 and 13.3% were caused by C cephalonica when alone, respectively. The actual percentage seed damage and weight loss attributable to A. fasciculatus were 0.1 and 0.9%, respectively.. There was correlation between insect density and damage caused. The free fatty acid level of cocoa beans was increased by 0.17% and 0.13% when infested by C. cephalonica and A. fasciculatus, respectively.
Bio-rational control of red flour beetle Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in stored wheat with Calneem® oil derived from neem seeds
(Journal of Pest Science, 2010-09) Adarkwah, C.; Obeng-Ofori, D.; Büttner, C.; Reichmuth, C.; Schöller, M.
The red flour beetle, Tribolium castaneum (Herbst), is one of the most serious secondary pests that feeds on a wide range of durable stored products including cereals, cereal products and other high value produce such as cocoa beans and dried fruits. Toxicity and protectant potential of Calneem® oil derived from the seeds of the neem tree Azadirachta indica A. Juss. towards T. castaneum were evaluated in stored wheat in the laboratory using contact toxicity, grain treatment, persistency, progeny emergence and repellency assays. Calneem® contains about 0.3% azadirachtin as its major active ingredient. The Calneem® was applied at six dosages (0.1, 0.2, 0.5, 1.0, 2.0 and 3.0% v/v). The oil was emulsified with water using 0.07% soap. All dosages of Calneem® oil were toxic and highly repellent to T. castaneum with an overall repellency in the range of 52-88%. The highest dosage of 3.0% of Calneem® oil tested killed at least 90% of the beetles within 72 h on grain, and 88% mortality was obtained on filter paper. T. castaneum mortality was dose dependent. The development of eggs to adults on cracked wheat was significantly (P > 0.05) inhibited by Calneem® oil treatments. The effectiveness of Calneem® oil was significantly reduced by the length of storage after application. The results obtained suggest good potential for the practical use of Calneem® oil as grain protectant for stored product pest control. The use of plant materials such as neem oil may be a safe, cost-effective method of grain preservation against pest infestation amongst low-resource poor farmers who store small amounts of grains. © 2010 Springer-Verlag.
Biological Effects of Neem Oil and Neemazal against the Larger Grain Borer, Prostephanus Truncatus (Horn) (Coleoptera: Bostrichidae) on Stored Maize
(University of Ghana, 2001-07) Aidoo, I.E.; Obeng-Ofori, D.; Akuamoah, R.K.; Cudjoe, A.R.; University of Ghana, College of Basic and Applied Sciences, School of Biological Sciences, Department of Animal Biology and Conservation Science (DABCS)
The biological activity of neem oil and neemazal against the larger grain borer, Prostephanus truncatus (Horn) was assessed in maize grain in the laboratory. The bioassays carried out were toxicity of the products against adults and immature stages, effect of the products on progeny production, damage assessment, repellent action and persistency of the products in grain and their effect on seed viability. Neemazal was highly toxic to P. truncatus than neem oil. The highest dosage of 0.8 ml killed 100 % adults of P. truncatus after 72 h exposure but the same dosage of neem oil evoked 70 % mortality after 96 h. The products were also active against the eggs and larvae causing a significant mortality. Neemazal provided greatest protection of maize grains with no noticeable feeding holes on grains treated with 0.6 and 0.8 ml/gm. Both products were moderately repellent to P. truncatus causing less than 50 % repellency. Activity of the two products significantly declined in treated grain after 24 h of storage following treatment. Neem oil and neemazal increased water absorption by maize seeds. Furthermore, seed germination was not affected by neem oil but neemazal significantly reduced seed germination. For the control of P. truncatus in stored maize, neemazal offers greatest protection against both the immature stages and adults. The non-toxicity of neem products to man and other beneficial organisms emphasize the potential use of these products as protectants of farm gate grain storage of small holdings in rural communities in Ghana and other parts of Africa where the neem is abundant.
Biological efficacy of CalneemTM oil against the tropical warehouse moth Ephestia cautella (Lepidoptera: Pyralidae) in stored maize
(International Journal of Tropical Insect Science, 2010-12) Shehu, A.; Obeng-Ofori, D.; Yao Eziah, V.
The tropical warehouse moth Ephestia cautella (Walker) is an important storage pest of maize grain. The control of this major moth pest relies heavily on the use of synthetic insecticides. We assessed the biological efficacy of a commercial neem oil (Calneem oil) against E. cautella in the laboratory, using the common grain protectant Actellic as a positive control. Contact toxicity, repellency, effects on oviposition, development and grain damage were assessed. The assays were conducted by treating 100 g of maize grains with Calneem oil concentrations of 3, 5 and 7 ml/l; and Actellic at 2 ml/l. Calneem oil significantly (P < 0.05) reduced oviposition rate, development of eggs and immature stages, and emergence rate of E. cautella progeny in maize grains. Grains treated with Calneem oil had significantly (P < 0.05) reduced grain damage in storage, and the oil had a repellency of 53-70% compared with the negative control. Calneem oil protected maize grain against damage by E. cautella for 10 weeks, compared with 20 weeks protection by Actellic. There was no resistance development to the oil for three generations of E. cautella. The insects that survived treatment with the LC90 concentration (12.2 ml/l) of the Calneem oil laid fewer eggs, and some of their progeny were deformed. Calneem oil provided a good level of protection to maize grains against infestation by E. cautella, and may therefore be a suitable substitute for Actellic. © 2010 icipe.
Causes of low productivity of cocoa in Ghana: Farmers' perspectives and insights from research and the socio-political establishment
(NJAS - Wageningen Journal of Life Sciences, 2004-12) Dormon, E.N.A.; Van Huis, A.; Leeuwis, C.; Obeng-Ofori, D.; Sakyi-Dawson, O.
Ghana is a major producer of cocoa in the world and relies heavily on the crop for foreign exchange revenue. However, production declined since the mid-1960s, reaching its lowest level in 1983, Although production has increased consistently since the mid-1980s, it still is less than the level attained in the mid-1960s. The decline is partly a result of decreasing areas under cultivation. Another problem in cocoa production in Ghana is low yields per ha, which is attributed to the incidence of pests and diseases, a low producer price, and non-adoption of research recommendations. Based on the idea that current research and extension messages might insufficiently address farmers' actual problems and context, a diagnostic study was carried out to better understand farmers' views on the problems of cocoa production. The study was conducted in three villages in the Suhum-Kraboa-Coalter District, Eastern Region, Ghana. An action research approach was followed to gather and analyse qualitative data with the objective of stimulating collective action in subsequent research activities with the farmers. Low productivity was identified as the main problem and the causes were classified into biological and socio-economic factors. The biological factors include the incidence of pests and diseases, most of which have received extensive research attention in Ghana, and of epiphytes, which have been neglected. The socio-economic causes were indirect and include the low producer price and the lack of amenities like electricity, which leads to migration, with as a result labour shortages and high labour costs. From the study it can be concluded that the biological and socio-economic causes of low productivity are inter-related in such a manner that tackling them separately will not overcome the problem unless the socio-technical nature of the causes are recognized and tackled in a holistic way. In this context, current interventions by research and extension seem to ignore important aspects of the problematic situation. Although the study shows the relevance of using a diagnostic approach, it is argued that outcomes may be affected by various contextual factors, including stakeholder selection and the relationship between the researcher and the participants. Hence, the outcomes of a diagnostic study should be approached with care.
Comparative susceptibility of Adult Africa Invader fly, Bactrocera invadens (Diptera: Tephritidae) to some selected insecticides
(Journal of Agricultural Science, 2012) Abdullahi, G.; Sule, H.; Obeng-Ofori, D.; Afreh-Nuamah, K.; Billah, M.K.
With the recent introduction of B. invadens in Africa and its devastating role in crop production, especially mango, with currently no registered insecticides for use against this fly in Ghana, the susceptibility of the fly to four commercially available insecticidal products namely, Cydim Super, Pyrinex 48 EC, Diazol 50 EW and Deltapaz was evaluated in the laboratory. The bioassay was conducted using three (3) different doses of each insecticidal product, by dipping 4x4 cm hardboard panels into the respective doses. Susceptibility of the flies to insecticides were assessed on freshly treated panels, 3-day-old and 6-day-old treated panels in some ventilated transparent bottles of 1 litre capacity. Adult flies aged between 4-12 days were used for the bioassays. The bioassay results indicated that the adult flies were more susceptible to Diazol (Diazinon) (LC50 = 0.6 ml/L; LC90 = 1.3 ml/L) and Pyrinex (Chlorpyrifos) (LC50 = 0.8 ml/L; LC90 =1.0 ml/L), and hence gave the least LT50 and LT90 times. Least susceptibility was recorded with Deltapaz (Deltamethrin) (LC50 = 3.1 ml/L; LC90 = 5.2 ml/L). It could be concluded that the control of B. invadens can be achieved more effectively by the use Pyrinex (Chlorpyrifos) and Diazol (Diazinon). The use of Pyrinex appears to be more economical to the resource poor farmers as it had least LC90 of 1.0 ml/L compared to 1.3 ml/L for Diazol in 30 min.
Converging farmers' and scientists' perspectives on researchable constraints on organic cocoa production in Ghana: Results of a diagnostic study
(NJAS - Wageningen Journal of Life Sciences, 2004-12) Ayenor, G.K.; Röling, N.G.; Padi, B.; Van Huis, A.; Obeng-Ofori, D.; Atengdem, P.B.
A diagnostic study was conducted to identify the major constraints on organic cocoa production at Brong-Densuso and surrounding communities in the Suhum-Kraboa-Coaltar District, Eastern Region, Ghana. The study followed a technographic study that highlighted cocoa as a public crop requiring broad techno-social innovations, In the technographic study, problems identified included low yields, persistent pest management constraints and a low adoption rate of technologies developed by the Cocoa Research Institute of Ghana. The diagnostic study adopted a Participatory Learning and Action Research approach to set up and implement fieldwork with relevant stakeholders leading to problem identification, prioritization, and collective design of an action plan (research agenda). Cocoa farmers within the study area are conscious of the environmental problems associated with the use of inorganic pesticides and the high cost of using them. Hence, they produce cocoa without applying any pesticides. Quite recently, however, their association with an organic marketing company led to a search for non-chemical pest and disease control measures and for ways to certify their cocoa beans as organic. A misconception as to what species of cocoa pests constitute 'capsids' was settled between farmers and scientists using a cage experiment on capsid damage. The farmers became convinced that the Cocoa Mosquito (Helopeltis spp.) (Hemiptera: Miridae), which they had previously considered an important pest, was a capsid species that caused little or no damage to the beans inside the pods. After this clarification, damage caused by the Brown Capsid (Sahlbergella singularis; Hemiptera: Miridae) and the Black Capsid (Distantiella theobroma; Hemiptera: Miridae) emerged as the most serious production constraint, followed by Black Pod disease (caused by Phytophtora palmivora). The malfunctioning of tenure agreements and the mistrust between landlords, who are mainly absentee farmers, and their caretaker cocoa farmers pose a serious threat to pest management innovations, especially where pruning to control Black Pod disease and uprooting trees infected with Swollen Shoot disease are concerned. The key stakeholders involved in the study agreed on three innovative (organic) capsid control methods for further research: the use of sex pheromone traps, crude aqueous neem (Azadirachta indica) seed extracts, and the use of ant (Oecophylla longinoda) colonies as biological control agents, the latter being proposed by farmers, The paper reflects on the diagnostic study as a continuous process in response to a continually changing context even beyond the end of the diagnostic research phase.
Deployment of the cowpea aphid resistance gene for cowpea improvement in Ghana
(University of Ghana, 2014-07) Kusi, F.; Asante, S.K; Padi, F.K; Obeng-Ofori, D.; University of Ghana, College of Basic and Applied Sciences, School of Agriculture, Department of Crop Science
Resistance to the cowpea aphid is important component of integrated pest management of cowpea cropping systems most especially at the vegetative stage. The objective of this study was to demonstrate the effectiveness of the aphid resistance locus identified in advanced breeding line SARC 1-57-2 in reducing damage from the cowpea aphid in Ghana. Using an F2 population developed from Apagbaala x SARC 1-57-2, the resistance locus was tagged with the SSR marker CP 171F/172R with a recombination fraction of 5.91%. Based on the CP 171F/172R, recurrent marker assisted backcrossing was carried out to introduce the resistance locus into the susceptible cultivar, Zaayura. This led to the development of several BC4F3 lines that are isogenic except for the region of the resistance locus. In field tests under no insecticide protection, the BC4F3 lines carrying the dominant marker allele suffered 3% loss of biomass and 4% loss of grain yield compared with plots protected with recommended insecticides. The BC4F3 lines carrying the recessive marker allele recorded 12% loss of biomass and 33% reduction in grain yield compared with the sprayed plots. The resistance locus did not influence the number of days to flowering or maturity and no pleiotropic effects were observed in terms of plant morphology or seed characteristics. In all segregating populations analysed, the locus segregated as a single Mendelian gene. Stability of the resistance locus was conducted at 18 locations covering six important cowpea growing Regions in Ghana. The range of damage by the pest on resistant and susceptible progenies were consistent across locations, and did not support the hypothesis of existence biotypes of the insect (based on differences in feeding damage on different varieties) in Ghana. This stability in performance places a premium on the resistance locus in improving cowpea cultivars developed for different agro-climatic regions of the country for resistance to the pest. The study has demonstrated the effectiveness of an insect resistance locus in significantly reducing insect damage under typical cowpea production conditions in Ghana
Effect of temperature on immature development and longevity of two introduced opiine parasitoids on Bactrocera invadens
(Journal of Applied Entomology, 2013-09) Appiah, E.F.; Ekesi, S.; Salifu, D.; Afreh-Nuamah, K.; Obeng-Ofori, D.; Khamis, F.; Mohamed, S.A.
Temperature-dependent development, parasitism and longevity of the braconid parasitoids, Fopius arisanus Sonan and Diachasmimorpha longicaudata Ashmed on Bactorcera invadens Drew Tsuruta & White, was evaluated across five constant temperatures (15, 20, 25, 30 and 35°C). Developmental rate decreased linearly with increasing temperature for both the parasitoid species. Linear and Brière-2 nonlinear models were used to determine the lower temperature threshold at which the developmental rate (1/D) approached zero. For F. arisanus, lower thresholds to complete development estimated with the linear and nonlinear models were 10.1 and 6.9°C, respectively. The total degree-days (DD) required to complete the development estimated by the linear model for F. arisanus was 360. In D. longicaudata, the linear and nonlinear models estimated lower thresholds of 10.4 and 7.3°C, respectively, and the total DD estimated was 282. In F. arisanus, percentage parasitism differed significantly across all temperatures tested and was highest at 25°C (71.1 ± 2.5) and lowest at 15°C (46.4 ± 1.4). Parasitoid progeny sex ratio was female biased at all temperatures except at 20°C. In D. longicaudata, percentage parasitism was highest at 20°C (52.2 ± 4.0) and lowest at 15°C (27.7 ± 2.5). Parasitoid progeny sex ratio was female biased and similar for all temperatures. Adult longevity of both parasitoids was shortest at 35°C and longest at 15°C, and females lived significantly longer than males at all temperatures tested. Our findings provide some guidance for future mass rearing and field releases of the two parasitoids for the management of B. invadens in Africa. © 2013 Blackwell Verlag, GmbH.
Efficacy of Calneem derived from Ghanaian neem seeds and seed oils from two locations in Cameroon against Sitophilus zeamais (Coleoptera: Curculionidae) on maize
(International Journal of Tropical Insect Science, 2011-12) Nchiwan Nukenine, E.; Tchiegang, C.; Andrine Tagne Mekouo, A.; Haman Tofel, K.; Adarkwah, C.; Obeng-Ofori, D.; Adler, C.
Botanical insecticides are among the most promising alternatives to synthetic insecticides for stored product protection. Calneem oil from Ghana and local neem oils from two localities in northern Cameroon (Garoua and Maroua) were tested at 0 (untreated control), 2, 4, 6, 8 and 12-ml/kg, on the adult and immature stages of the maize weevil Sitophilus zeamais (Motschulsky), for mortality and reproduction inhibition. The neem oils from Cameroon were extracted using the traditional kneading method and a hydraulic press in the laboratory (refined). Maize grains were coated with the five neem seed oils (Calneem, Garoua traditional and refined, and Maroua traditional and refined, respectively) and adult mortality was recorded at 1, 3, 7 and 14 days after exposure. Within 1 day of exposure, the highest tested concentration (12-ml/kg) of Calneem, Garoua traditional, Garoua refined, Maroua traditional and Maroua refined oils caused similar weevil mortality of 86.3, 93.8, 93.8, 97.5 and 97.5%, respectively. The 24-h LC50values for the oils in the same order were 7.0, 6.0, 5.0, 5.0 and 4.8-ml/kg, respectively. The lowest (2-ml/kg) and highest (12-ml/kg) concentrations of the oils suppressed progeny production by over 80 and 98%, respectively. The oils arrested the development of the hidden eggs and immature stages in the maize grains. The results suggested that neem seed oils from different localities of northern Cameroon, irrespective of the method of extraction, were effective for the protection of stored maize against S. zeamais. The promotion of natural neem seed oils as stored grain protectants in Cameroon would boost food security, alleviate poverty and reduce environmental degradation. © 2011 ICIPE.
Efficacy of four protectants applied to stored bambarra groundnut against infestation by Callosobruchus maculatus (Fab.)
(University of Ghana, 1998-06) Dankwa, J.A.; Obeng-Ofori, D.; University of Ghana, College of Basic and Applied Sciences , School of Biological Sciences , Department of Animal Biology and Conservation Science (DABCS)
Bambara groundnuts are good nutrient sources of high protein and carbohydrate contents. The seeds suffer damage through infestation by Callosobruchus maculatus (Fab.) during storage. The efficacy of four protectants, namely actellic, steam, neem seed oil and neem kernel oil were tested on two varieties of Bambara groundnuts namely, Jabajaba and Piele Balgu. Efficacy of the different treatments was demonstrated on Bambara groundnut through the number of adult C. maculatus that emerged. Actellic, steam and neem seed oil significantly (P<0.05) reduced emergence of C. maculatus on the seeds of the varieties used. Consequently these treatments also significantly (P<0.005) reduced the number of seeds that were damaged through C. maculatus infestation. Damage of seeds of the Piele Balgu variety ranged from 1.1 (actellic treated) to 30.4 (neem kernel oil treated). In the Jabajaba variety, seed damage ranged from 1.1 (actellic treated) to 28.6 (untreated). Each of the four treatments, however, significantly (P<0.05) reduced C. maculatus infestation in the order of Actellic >Steam > Neem seed oil > Neem kernel oil. Persistence of treatment effects were tested for 90 days after treatment (due to time constraint). It was established that the seed testa of Jabajaba Bambara groundnut renders it less susceptible to C. maculatus infestation. Actellic did not lose its efficacy 90 days after treatment. Steam and neem seed oil significantly (P<0.05) reduced infestation of legumes by Callosobruchus maculatus. Germination of treated seeds showed that steam treatment had a lethal effect on the \ seeds used. Neem seed oil promoted germination whilst Actellic significantly (P<0.05) reduced the activity. Neem seed oil promoted more vegetative growth in the Piele Balgu variety than in the jabajaba variety. Protein content of treated Bambara groundnut seeds did not change significantly (P>0.05) from the untreated. Seeds of the jabajaba variety have more protein than the Piele Balgu seeds which were instead more susceptible to C. maculatus infestation. Neem seed oil offers a good protection to seeds of Bambara groundnut, does not affect the protein content and germination potential of seeds and can therefore be used as a substitute for actellic.
Efficacy of mixing vegetable oils with pirimiphos-methyl against the maize weevil, Sitophilus zeamais Motschulsky in stored maize
(Journal of Stored Products Research, 2005-05) Obeng-Ofori, D.; Amiteye, S.
Sitophilus zeamais is a major insect pest of stored maize and grain products in the tropics. The toxicity of coconut, groundnut and soybean oils applied at 1, 2, 5 and 10ml/kg and pirimiphos-methyl at 2.5, 5 and 10μl active ingredient in 2ml of water/kg of grain (116, 18 and 14 of the recommended dose), alone or in combination, to adults and immature stages of S. zeamais, the persistence of the treatments in maize grains and their effects on seed viability were evaluated in the laboratory. All the treatments caused significant mortality compared to untreated controls. Low dosages of the oils and pirimiphos-methyl when combined were highly toxic to adult S. zeamais. The mixtures completely inhibited the development of immature stages of the weevil. Only pirimiphos-methyl and the mixtures retained some activity 60 days after application. Pirimiphos-methyl can be used at reduced rates if combined with vegetable oils to control infestations of S. zeamais in stored maize. © 2004 Elsevier Ltd. All rights reserved.
Efficacy of Neem oil and Neemazal against the Larger Grain Borer, Prostephanus truncatus (Horn) in stored maize
(Journal of Ghana Science Association, 2009) Boateng, B.A.; Aidoo, I.E.; Obeng-Ofori, D.; Cudjoe, A.R.; Akuamoah, R.K.
The biological activity of neem oil and Neemazalon adult and immature stages of the larger grain borer, Prostephanus truncatus, as well as on its F1 progeny was assessed in stored maize in the laboratory. Repellency and persistency effects of the treatments in grain as well as the effect of the treatments on grain damage were also determined. Neemazal was more toxicto P. truncatus than neem oil. The highest dosage of 0.8ml/200g grain killed 100% adult P. maculatus after 72 h exposure but the same dosage of neem oil resulted in 70% mortality after 96h. The products also caused significant (p<0.05) mortality in P. truncates eggs and larvae, Neemazal provided greater protection to maize grains with no noticeable boreholes on grains' treatedwith 0.6 and 0.8ml/200g grain. All treatments repelled less that 50% P. truncatus adults. Activity of the two product significantly declined (0<0.05) in treated grain after 24 hour of storage following treatment. Neemaza loffered greater protection against both immature stages and adults of P. truncatusin stored maize.
Efficacy of the Multiple-Layer Hermetic Storage Bag for Biorational Management Of primary Beetle Pests of Stored Maize
(IDOSI Publications, 2012) Anankware, P.J.; Fatunbi, A.O.; Afreh-Nuamah, K.; Obeng-Ofori, D.; Ansah, A.F.
This paper reviews the destructive effects of Prostephanus truncatus and Sitophilus zeamais on maize grain and the effectiveness of the triple-layer hermetic bag storage system as a control measure. Maize (Zea mays L.) is the most important cereal in Ghana and is the staple food for over 90% of the population. The availability and safety of this important food crop is threatened by insect pests, rodents and fungal attacks due to inappropriate storage methods. Infestation by insect pests accounts for between 20 to 50% of post-harvest losses in maize. Pesticides and other artificial gaseous techniques are no longer acceptable due to food quality and environmental related issues. In the light of the foregoing, the hermetic storage techniques have recently been revisited as a way to control insect pest and other microbial attack in maize grain. The system creates an air tight environment to rapidly exterminate insect development and suppress micro flora activity. A recent development is the invention of the triple layer hermetic bag using biodegradable plastic materials. This is being investigated to determine its efficiency as a storage technique that prevents insect attack and yields product with good food quality and market acceptability. Quantitative figures are needed about the current distribution and losses caused by insect pests especially P. truncatus and S. zeamais. There is also the need to fill the knowledge gaps and provide adequate information needed to inform decisions for the use of the use of hermetic storage technology and its further refinement.
Estimation Of Postharvest Losses And Analysis Of Insecticide Residues In Some Selected Vegetable Crops In The Greater Accra Region Of Ghana
(University of Ghana, 2013-06) Amartey, J.N.A.; Obeng-Ofori, D.; Sarpong, D.B.; University of Ghana, College of Basic and Applied Sciences, School of Agriculture, Department of Crop Science
Small-scale farmers in the Greater Accra region of Ghana grow vegetable crops including tomato, cabbage, pepper, okra and garden eggs and apply many types of pesticides to control pests and diseases that attack these crops. This study was conducted in the Accra Metropolitan District, Adenta Municipal District, Ashaiman Municipal District, Dangme West District, Ga South Municipal District and Ga West Municipal District. The purpose of the study was to estimate the postharvest losses in the seleted vegetable crops incurred by the farmers and retail traders, determine pesticide use pattern of vegetable farmers and analyse specifically, the level of insecticide residues in okra sent to the market. The communities studied included Weija, Kojo Ashong, Kordeabe, Dawenya, Dzorwulu, Obaakruwa, Ashaiman, Atomic, Okushiabade and Onyaasanaa. A total of 100 farmers and 75 retailers were randomly selected for the studies. The various methods used for the study included questionnaire administration, physical observations and personal interviews. The vegetable farmers and traders were interviewed and both closed and open ended questionnaires were administered to them from November 2011 – March 2012 to assess the extent of postharvest loss and pesticide use pattern of the farmers. Okra samples from four farms namely Weija, Dawenya, Atomic and Ashaiman were sent to the Ghana Standard Authority for analysis of insecticide residues. It was confirmed that postharvest losses was a major problem experienced by vegetable crop farmers and traders. The losses were mostly caused by pests and diseases and poor handling. As a result farmers sprayed chemical pesticides to control them in order to meet market demands. From the study, percent estimated losses by farmers were 13% for cabbage and okra, 12% for pepper, 1% for eggplant, and 20% for tomato. About 15%, 7%, 8% and 10% were estimated lossess for cabbage, pepper and okra respectively. Loss for garden eggs was insignificant due to their ability to maintain their freshness till they were sold to consumers. Commonly applied insecticides included Auntie Ataa, Golan, Cydim Super, Attack; fungicides included Sulpur 80, Bendazim, Mangozeb and herbicides were Round up, Ejumawura and Paraquat. Only 5% of 100 farmers interviewed used neem extracts to control pests and diseases. Most farmers’ sprayed pesticides themselves but 10% employed skilled labour and the pesticide application was usually done in the mornings or evenings. Knowledge on the correct pesticide application was obtained from Ministry of Food and Agriculture staffs, pesticide dealers and colleague farmers. The farmers also attested to the fact that the chemical pesticides used were poisonous and caused various health hazards. Some compounds detected from the test conducted in the laboratory indicated the presence of Alpha-Endosulfan, Endrin, Fenvalerate, P,P’-DDE and Ethoprophos. The results generated indicated that the okra samples that were tested for insecticide residues were below EU’s Minimum Residue Levels (MRLs).