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Neem (Azadirachta indica) kernel powder (NKP) mixed 1:1 (weight basis) with some inert diluents (fine-sand, kaolin-dust, and saw-dust) were applied into the whorls of sorghum seedlings . Cost-benefit analysis shows that it was financially most beneficial to use NKP + fine-sand to control S. calamistis on sorghum in Nigerian Sudan savanna.

Post-harvest losses caused by Callosobruchus maculatus is a major constraint to cowpea production and the improper use of synthetic insecticides by most farmers have resulted in environmental, health hazards, and development of insecticide resistance in insects. This study evaluates the efficacy of solar heat treatment using double-layered black polypropylene sheets in suppressing the development of the cowpea bruchid eggs and the effect of the heat absorbed on the germination potential of cowpea seeds. Five pairs of 2 – 3-day old adult C. maculatus were allowed to oviposit for ten days on 50 g cowpea seeds in a glass jar in the laboratory before exposure to 24, 48, 72 and 96 h solar heat treatment regimes. Infested cowpea seeds but not exposed to solarization was set along with the treatments while uninfested cowpea seeds was also set along and used as part of the germinability test. The experiment was laid out in a completely randomized design and treatments were replicated four times. The results showed that there were no significant differences among the number of eggs laid by adult C. maculatus on the cowpea seeds before solar heat treatment. Solar heat treatment of the cowpea seed at 24 h achieved 100% egg mortality of C. maculatus thus preventing adult emergence. The effect of solarization on seed viability showed that there were no significant differences between the infested cowpea seeds exposed to different solar radiation regimes when compared to uninfested cowpea seeds – range; 74% – 99% germination. The results showed that 24 h solar heat exposure of cowpea seeds in double-layered black polypropylene sheets could be the thermal death point of C. maculatus eggs on the seeds in the study area.

Watermelon has been reported to be vulnerable to insect pest pressure throughout its growth stages with a resultant indiscriminate calendar-based insecticide application (of up to 25 sprays/season in the study area), with its attendant consequences. In order to recommend the crop growth period(s) to effect chemical control measures that will give better return on investment, field trials were set-up in the early- and late-cropping seasons of 2016 and 2017. Forty, 5m long x 8m wide plots were demarcated in randomized complete block design in 4 replications. Treatments were applications of 0.5% Cyper-diforce® (Cypermethrin 30g/L + Dimethoate 250g/L) at seedling, mid-vegetative, mid-flowering, mid-fruiting stages and their combinations. Unsprayed plots served as control. Pest and beneficial arthropod density, leaf injury, crop growth and yield data were collected and subjected to variance analysis and significantly different means were separated by SNK at 5% level of probability. Cost:benefit ratios of the various treatments was also computed. Findings indicate that, leaf-eating beetles had the highest impact on stand survival and yield. Insect pest density and damage generally decreased with increase in frequency of insecticide application and treatment differences were significant (p< 0.05) except in the case of A. gossypii in the late-sown crop of 2017. Plot sprayed at seedling + vegetative + fruiting stages gave the highest fruit yield and return on investment. It is therefore suggested that, for economic production of watermelon, the crop should not be sprayed during the flowering period.

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