Tannin extracts of two sorghum, Sorghum bicolor (L.) Moench. cultivars, BKS5 and BTX 623 were assessed for their bioactivity against the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and the angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae), in whole wheat flour pellets, and against the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in whole wheat flour at three treatment levels. The number of adult progeny was reduced and number of days to emergence increased by tannins extracted from both sorghum cultivars at all treatment levels. However, the effects were not significant in all cases. In a short-term (25 days) feeding test using S.oryzae adults, the presence of sorghum tannins from cv. BKS 5 in the pellets significantly reduced feeding by the insects.

Investigations were conducted in the greenhouse to evaluate the biological performance of Aphis fabae Scopoli when bred on two varieties of the common bean, Phaseolus vulgaris L. Mean developmental period of the aphid was 7.8 days at 26.5°C (range 15.0–32.5°C) on the bean varieties Mwezi Moja (GLP.10) and Red Haricot (GLP.3). The reproductive life of the aphid averaged 15.3 days (range 11–17 days) during which each mother aphid produced on average 55.2 and 56.2 nymphs on the two bean varieties, respectively. Nymphs (66.2%) were born during the daytime (0600–1800 hr), whereas only 33.8% of the nymphs were produced during the night (1800–0600 hr). There were two peaks of diurnal nymphal production, and more nymphs were born during the morning peak (0600–0800 hr) than during the mid-afternoon peak (1400–1600 hr). A very high rate of A. fabae population increase was observed.