Effects of topical application of two juvenile hormone analogues (JHAs), R-20458 (6, 7-epoxy-1(p-ethylphenoxy)-3, 7-dimethyl-2-octene) and ZR-512 (ethyl 3, 7, 11-trimetnyl-2, 4-dodecadienoate) on reproduction and longevity of mustard aphid, Lipaphis erysimi (Kalt.) were investigated. Doses of the JHAs as high as 2 μg per aphid failed to reduce the fecundity of the aphid though initial reduction in the daily reproduction was observed. Also, the doses which induced morphogenetic abnormalities at the third-instar, could not affect embryogenesis.

In two study seasons, viz. summer (March to May) and “kharlf” (August to October) 1984 at Bangalore, India, populations of Aphis craccivora Koch on cowpea increased rapidly with crop growth and their peak coincided with peak pod formation. The activity of predatory coccinellids started 1 to 3 weeks after the appearance of aphids. The peak predator population more or less coincided with the peak aphid population. Highly significant positive correlations were found between weekly aphid and predator populations in the two seasons. The prey to predator ratio reached higher values 2 weeks after the incidence of the aphid, during peak pod formation stage and at the time of harvest. Amongst the predatory coccinellids, Menochilus sexmaculatus (F.) was predominant in both seasons constituting 77–88% and 83–95% of total predator population during summer and “kharif”, respectively. The study demonstrated a prey-dependent predator growth, often lagging behind that of the prey, pressing the need for alternate control methods that can be integrated into the management strategy considering the weather factors such as rainfall.

Insect pests are major constraints in cowpea production. Breeding for insect resistance is a major objective of cowpea improvement programme at IITA. Resistance to leafhoppers and aphids has been incorporated in advanced breeding lines thus eliminating the need for other control measures. Similarly, a moderate level of resistance to thrips and cowpea storage weevil has also been incorporated thus reducing the damage due to these two pests. A moderate level of resistance to legume pod-borer and pod sucking bugs has also been identified and is being incorporated in advanced breeding lines. The long term strategy is to develop cowpea cultivars with multiple resistance to insect and diseases with superior agronomic characters and local adaptability.