Laboratory bioassay tests showed that Bacillus thuringiensis (B.t.) (Bactospeine) treatment of second instar larvae of Heliothis armigera (Hbn.) and Spodoptera litura F. increased their susceptibility to endosulfan, monocrotophos, fenvalerate and cypermethrin. The LC50 of these insecticides to both the species of larvae were lowered when treated with B.t. Comparison of susceptibility ratios showed that the increased susceptibility to insecticides was more in H. armigera than in S. litura larvae.

Studies on critical time of insecticidal protection in relation to damage by aphid, Aphis gossipii Glover and leafhopper, Amrasca biguttula biguttula Ishida on plant growth and yield of okra revealed that 21–42 days after germination, was the most critical time prior to fruiting. Application of carbofuran at the time of sowing was redundant. Effective plant protection 21–42 days after germination resulted in lowest leafhopper and aphid infestation and subsequently the highest benefit to cost ratio.

Management programmes for the use of action thresholds to initiate insecticide treatments for controlling pod-borer, Adisura atkinsoni on field bean were evaluated in comparison with standard sprays on calendar basis. Results of three field experiments revealed that management based on initial spray at peak egg laying on tender pods, followed by sprays to maintain 1.5 flat pod damage/inflorescence realised maximum benefit: cost ratio. This management also resulted in reduced insecticide usage.

The relative susceptibilities of 43 cowpea varieties to damage by Cydia ptychora (Meyrick) under chemical protection with monocrotophos, were investigated in field trials at Ile-Ife, Nigeria. The results revealed significant varietal differences, with the moderately resistant varieties ER-7, BPL-3-1 and EW/1 consistently showing relatively low damage. These varieties may be useful in planning an integrated pest management programme involving minimum insecticide treatment.