Thirty-six cowpea cultivars were evaluated for their resistance to the pod-sucking bug, Clavigralla tomentosicollis Stål, in the screenhouse and in field experiments. Absolute resistance was not found in any of them, although cultivars with relatively low percentage seed damage were present. Seventeen cultivars were significantly less damaged than the susceptible check in the field experiments. Seven cultivars had less than 60% seed damage. Of these, TVu 3354, TVu 3355, TVu 3372, TVu 8525 and TVu 3199 were the least damaged. Per cent seed damage on cultivars in the field was not consistent with that in the screenhouse, because of the influence of other pod-sucking bug species and environmental factors.

Yield components such as 100 seed weight and the number of pods per plant were related to the resistance of the test cultivars to the bug attack. Cultivars with smaller seeds and more pods per plant were less damaged. The number of seeds per pod was not related to the degree of seed damage. Similarly, morphological parameters of the cultivars were not related to the degree of seed damage.

Insect pests are major yield reducers in sorghum under traditional farming practices in Africa. The use of resistant varieties in an integrated pest management scheme provides the most cost effective and practical means of sorghum insect control. Corneous grain sorghums are more weevil resistant than their softer endosperm counterparts. A wide range of sources of resistance to shootfiy, stem-borer and greenbug are known. Breeding for resistance to sorghum insects has been practised with varying degrees of success. Greenbug resistance breeding in sorghum has been successful in the U.S.A. Stem-borers are perhaps the most serious group of sorghum insects in Eastern Africa and further efforts are needed in breeding for resistance to these pests. In an effective pest resistance breeding work, the breeder and the entomologist must work as a team to make the fastest possible progress. Where several pests are of concern in an area, genotypes with multiple resistance in good agronomic backgrounds are needed.

Orseolia oryzae, the rice gall midge, is a major pest of rice in many areas of tropical Asia and is becoming an important pest in Africa. A chronological review of the progress made in various national programmes on varietal resistance, sources of resistance and breeding for resistance is given. Many resistant varieties have been identified and have been utilized in breeding programmes to develop high yielding varieties with multiple resistance to the gall midge and other insect pests and diseases. Mechanisms and inheritance of resistance in rice varieties are discussed. Rice varieties resistant in various countries and sources of resistance used in breeding programmes are listed. Biotype variations in different countries and within the countries are revealed, and a preliminary classification of gall midge biotypes based on varietal reactions is proposed.