Abs tract. Pigeonpea is one of the major legume crops grown in eastern Africa but has been relatively neglected in terms of research and development. The peas are a rich source of protein and the crop is nitrogen-fixing and drought tolerant. It is an ideal crop for the semi-arid areas of Africa and there is great potential for it to be more widely grown. The large number of pests and diseases which attack pigeonpea in Africa (and elsewhere) is perhaps the main constraint to increased production. The most important pest worldwide is the pod borer, Helicoverpa armigera, but the flowers and pods are attractive to a wide range of insect pests. The most important disease in eastern Africa is Fusarium wilt (Fusarium udum) and considerable effort has been devoted by ICRISAT to developing wilt-resistant pigeonpeas, adapted to cultivation in the region. This paper reviews the literature on pests and diseases of pigeonpea with special reference to eastern Africa and presents some new information on distribution and damage levels for the key pests and diseases.

A study conducted in Uganda on Callosobruchus chinensis showed that adults emerging from dry seed-infested and immature pod-infested pigeonpea diered in a number of morphological and biological characteristics in one or both sexes. Adults emerging from dry seed-infested pigeonpea were more or less uniform in a number of these characteristics; in contrast, adults emerging from green podinfested pigeonpea diered depending upon when they emerged: the dierences were greatest between those emerging during the 2nd to the 6th days from ®rst emergence, and those emerging from the 8th to the last days of emergence. In one or both sexes, these dierences were expressed in terms of elytral hue and size, body length, distance between the compound eyes, length of pygidium, body water content, pre-maturation periods, fecundity and adult longevity. We suggest that these dierences are due to polymorphism, and speci®cally the predominance of¯ight forms among late emergers from pod-infested pigeonpea. The dierences observed in the two morphs of C. chinensis and ascribed to the¯ight and ightless forms, are thought to be adaptations for survival and propagation under ®eld and storage conditions, respectively. The predominance of emerged adults of the¯ightless forms from dry seed and the¯ight forms from green pods were associated with low moisture content in dry seed and high moisture content in green pods, respectively. These observations show that bruchid control measures are needed in the ®eld as well as in storage.

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Investigations with pigeonpea (Cajanus cajan) genotypes`Apio-elina' and`PI-397566' showed that certain pod characteristics in¯uenced both infestation in the ®eld by Callosobruchus chinensis and damage caused by this pest. Compared to pods with no or sparse hair, pods with thick hairs suered greatly reduced ®eld infestation due to the barrier eect of the hairs on oviposition and larval penetration. Even on pods with no or few hairs, the pod wall appeared to oer some resistance to both larval penetration and adult emergence. High levels of infestation by C. chinensis were recorded on pigeonpea pods with no or few hairs, those with pods damaged through shattering, and those with pods that had been previously damaged by pod borers. From the results of the study, it was recommended that pigeonpea selection should include screening for high pod hair density and thicker pod wall.