Effects of the interaction of two levels of the black bean aphid, Aphis fabae Scopoli (Homoptera: Aphididae), and four stages of plant growth and development on the performance of the common bean, Phaseolus vulgaris L., under greenhouse conditions in Kenya
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Damage caused by the black bean aphid, Aphis fabae Scopoli, on the common bean, Phaseolus vulgaris L., was severest when the aphids were transferred onto bean plants during the preflowering stage. There were significant reductions in the average length of the central shoot, production of flowers, pods and seeds per plant. Seed weight per plant was also significantly reduced when aphid infestation occurred during the preflowering stage. Smaller, but significant reductions to the length of the central shoot, quantity of pods and weight of seeds produced per plant caused by A. fabae were also recorded when the aphids were transferred onto plants at anthesis. When aphid infestation occurred during the grain filling stage the damage caused was minimal and insignificant. The results obtained indicated that the preflowering stage was the vulnerable stage of bean development during which aphid attack is most harmful and, if unchecked, could lead to drastic yield losses.