Three neem products—an emulsifiable concentrate of neem oil (NOEC), neem kernel water extract (NKWE) and neem leaf water extract (NLWE)—were applied on field cassava for protection against damage by the grasshopper, Zonocerus variegatus (L.). Three conventional insecticides viz. lindane 0.3%, cypermethrin 0.006% and monocrotophos 0.24% were also compared. All the neem products protected cassava for varying periods. Efficacies of NOEC and NKWE were superior to insecticides. From the results, neem products recommended to check the grasshopper damage were as follows: NOEC 0.5–2% to be applied every 8 days, NOEC 3–4% to be applied every 10 days, NKWE 7–10% to be applied every 12 days, NLWE 50% to be applied every 6 days.

Observations on the growth and development of Chilo partellus (Swinhoe) larvae under laboratory and field conditions indicate sexual dimorphism as well as a general developmental polymorphism. Larvae of both sexes went through fifth, sixth or seventh instars before pupation. The mean developmental period, larval head capsule width, and the number of instars before pupation as well as pupal weight were higher in the female compared to the male larvae. These observations suggest differences in the physiological state of fifth-instar larvae in a population; some of them might be in the penultimate, while others might be in the ultimate instar.

Juvenile hormone analogues (JHAs), JHA I (6,7′-epoxy-3′,7′-dimethyl-dec-2′-enyl 6-ethyl-3-pyridyl ether), JHA II (3′,7′-dimethyl-undec-2,6′-dinyl 6-ethyl-3-pyridyl ether), MV-678 (2-methoxy-9-[4-isopropyl phenyl]-2, 6-dimethylnonane), and R-20458 (4-ethylphenyl-6, 7′-epoxy-geranyl ether) in acetone solution were applied to insect diets at 10ppm (v/v), and their effects on four species of stored products beetles observed. The larvae of the flour beetles, Tribolium confusum Jacquelin duVal, and Tribolium castaneum (Herbst), reared in media treated with JHAs I and II failed to pupate. At the end of the 6-week observation period, these larvae had not yet pupated. MV-678 and R-20458 produced ecdysial failures, lethal morphological abnormalities and larval/pupal and pupal/adult intermediates. Only a few apparently normal adult flour beetles emerged from these treatments. The lesser borer grain beetle, Rhizopertha dominica (Fabricus), completely failed to reproduce in a medium treated with JHA I. JHA II, MV-678 and R-20458 affected the reproduction of the two grain beetles, R. dominica and Sitophilus oryzae (L.), to varying extent, with MV-678 being the least potent JHA.

Laboratory studies with Megalotomus parvus (Hemiptera: Alydidae), feeding on seeds or pods of legumes, and on different parts of the soybean plant, Glycine max, demonstrated that nymphal survivorship, developmental time and body weight at adult emergence, and adult reproductive parameters, survivorship, longevity and body weight changes, exhibited differences depending on the food source utilized. In general, mature soybean seeds (R8 stage) were the most suitable food. The greatest nymph and adult survivorship and the greatest adult longevity were obtained from this food source. Body weight at certain ages and fecundity of females was also greater on mature soybean seeds than on the other foods. Immature soybean seeds for nymphs, and soybean pods for adults, were the second most suitable food, followed by green beans, Phaseolus vulgaris and immature lupin, Lupinus luteus seeds (for nymphs) and lupin pods (for adults); nymph and adult performance was drastically reduced on lupin seeds'pods and no nymphs survived to adult on soybean stems or leaves. On all foods tested, duration of the nymphal stages differed significantly, with the first stage being the shortest, and the fifth the longest. Females achieved significantly greater body weight than males on all foods, except on lupin pods. Results of these laboratory studies and those of field observations suggest that mature soybean seeds are the most important food source in the seasonal phenology of M. parvus.

A field evaluation of nine chemicals was conducted at Cotton Research Station Kibos for their efficacy against bollworm and cotton stainer species attacking cotton in Kenya. Based on the yield and percentage stained seed cotton, Decis'Triazophos, pp 321 Karate and Baythroid and Decis were the most effective insecticides in 1985 and 1986 respectively. However, there was no consistency in results of performance of insecticides tested against cotton insects in the 2 years. The apparent poor performance of most insecticides tested against cotton insects was attributed to fixed insecticide spray schedule which resulted in superfluous and often mistimed chemical applications. It is therefore necessary to establish damaging threshold(s) of major cotton pests in this country so that chemicals can be efficiently used to control them with minimum adverse effects on our environment.