No abstract

The antifeedant activity of Neemix 4.5 EC, a commercial formulation of azadirachtin from the neem tree (Azadirachta indica A. Juss), was tested against adult Nezara viridula (L.) in the laboratory using a cowpea pod-dip method. A toxicity assay was conducted by dipping fourth-instar nymphs. Feeding by adults was significantly reduced in treated pods compared with controls, based on counts of salivary deposits on pod surfaces, inside pod walls and on seeds. The antifeedant effect of azadirachtin was significantly greater on pods treated with 5% aqueous solution than on those treated with 0.5%, indicating that the antifeedant activity was related to concentration. Bugs were initially repelled by Neemix before approaching treated pods to feed. The LC50 for nymphs was 61% (27450 ppm azadirachtin) at 2 d and ranged from 1.8 to 6.2% (810 to 2790 ppm) at 5 d post-treatment, which indicated that neem was slow acting. Sublethal treatment of nymphs disrupted molting and caused morphological defects in adults. Development time to adulthood also was prolonged, and longevity of females was reduced by neem treatments. Azadirachtin may provide an effective component of a comprehensive management program for N. viridula.

Yield trials are used in plant breeding programs to evaluate the yield potential and stability of selected lines. The objectives of this study were to evaluate yield potential, genotype × environment interactions, and stability of peanut genotypes for the savannah region of West Africa. Twenty peanut (Arachis hypogaea L.) genotypes were tested at two sites in Ghana and two sites in Burkina Faso in 2010 and 2011. The experimental design was a randomized complete block design with three replicates. Genotype, location, and genotype × environment interactions were highly significant, indicating genetic variability among genotypes across changing environments. Stability analyses showed that genotypes ICGV‐IS 96814, ICGV (FDRS)‐20 × F‐MIX 39, Gusie Balin (92099), ICGV‐IS 92093, and ICGV‐IS 92101 had broad adaptability, with above‐average yield across sites and a regression coefficient close to 1.0. Genotype ICGV‐IS 96814 produced the highest pod yield (1760 kg ha−1) across all environments and had a regression coefficient close to unity (b = 1.06). Therefore, genotype ICGV‐IS 96814 is less responsive to varied environmental and soil conditions. However, the released cultivar Nkatesari was considered equivalent in some respects because it had pod yield equal to ICGV‐IS 96814 but with a higher regression coefficient. High‐yielding cultivars, mostly from ICRISAT‐derived crosses, yielded nearly 80% more than the three farmer check cultivars TS 32–1, Doumbala, and Chinese, which had pod yields from 890 to 980 kg ha−1. The higher‐yielding cultivars had longer life cycle, greater leaf spot resistance, and higher partitioning than the farmer check cultivars.

No abstract

No abstract

A survey of 337 cotton farmers in the three northern regions of Ghana was conducted between November 2002 and March 2003 with the objectives of assessing farmers' knowledge and perceptions of cotton insect pests and examining their control practices. The survey revealed that between 69 and 86% of the farmers were illiterate. Farmers' age average 42 years and had an average of 9 years of cotton farming experience. Farmers were familiar with cotton insect pests, especially those whose feeding caused obvious symptoms in the field such as bollworms, leafrollers and cotton stainers. Farmers relied on chemical insecticides supplied by their contract cotton companies to control insect pests on their fields. Insecticides from three classes namely organochlorines (e.g. endosulfan), pyrethroids (e.g. Lambda-cyhalothrin), organophosphates (e.g. Chlorpyrifos) or their mixtures were used. An average of five applications were made during the season. Farmers indicated that the control practice was largely ineffective against the pests, and attributed the cause to the use of expired and inadequate quantities of chemicals. The study showed that only 28% of the respondents had some knowledge of alternative pest control measures. It is important to improve farmers' knowledge and management skills of cotton insect pests through participatory research and training in integrated pest management (IPM). IPM trainingthrough farmer field schools will help farmers to acquire the requisite knowledge and skills to improve their management of insect pests on their fields.

Cowpea [Vigna unguiculata (L) Walp.] is an important staple legume in the diet of many households in sub-Saharan Africa. Its production, however, is negatively impacted by many insect pests including bean pod borer, Maruca vitrata F., which can cause 20–80% yield loss. Several genetically engineered cowpea events that contain a cry1Ab gene from Bacillus thuringiensis (Bt) for resistance against M. vitrata were evaluated in Nigeria, Burkina Faso, and Ghana (West Africa), where cowpea is commonly grown. As part of the regulatory safety package, these efficacy data were developed and evaluated by in-country scientists. The Bt-cowpea lines were planted in confined field trials under Insect-proof netting and artificially infested with up to 500 M. vitrata larvae per plant during bud formation and flowering periods. Bt-cowpea lines provided nearly complete pod and seed protection and in most cases resulted in significantly increased seed yield over non-Bt control lines. An integrated pest management strategy that includes use of Bt-cowpea augmented with minimal insecticide treatment for protection against other insects is recommended to control pod borer to enhance cowpea production. The insect resistance management plan is based on the high-dose refuge strategy where non-Bt-cowpea and natural refuges are expected to provide M. vitrata susceptible to Cry1Ab protein. In addition, there will be a limited release of this product until a two-toxin cowpea pyramid is released. Other than South African genetically engineered crops, Bt-cowpea is the first genetically engineered food crop developed by the public sector and approved for release in sub-Saharan Africa.

Pod shattering (dehiscence) is a major constraint to soybean (Glycine max. (L) Merrill) production in the northernsavanna zones of Ghana, but research on improving soybean for resistance to shattering is scanty. Genetic analysis of resistance to pod shattering was undertaken on three soybean crosses involving resistant and susceptible varieties to determine broad-sense (h 2 bs ) and narrow-sense (h 2 ns ) heritability, minimum number of genes (MNG) involved cytoplasmic inheritance, and allelic relationship between shattering and non-shattering. Mean h 2 bs was 0.92 (range 0.90-0.95), and mean h 2 ns was 0.46 (range 0.40-0.53), indicating the importance of both additive and non-additive variances and that shattering resistance can be improved through breeding. Mean MNG controlling shattering resistance was 2 (range 1-3), indicating that genes for shattering resistance differed among parental lines. There was no difference between the mean of any F 1 population and it's reciprocal, indicating lack of maternal/cytoplasmic influence and that the character was under nuclear gene control. Observed F 2 ratios revealed that inheritance of resistance to pod shattering in soybean was qualitative in nature and under the 18 H. Mohammed et al. influence of either duplicate recessive or dominant and recessive epistasis, depending on the parental genotypes used in the cross.