The legume pod borer, Maruca vitrata, is an endemic insect pest that causes significant yield loss to the cowpea crop in West Africa. The application of population genetic tools is important in the management of insect pests but such data on M. vitrata is lacking. We applied a set of six microsatellite markers to assess the population structure of M. vitrata collected at five sites from Burkina Faso, Niger and Nigeria. Observed polymorphisms ranged from one (marker 3393) to eight (marker 32008) alleles per locus. Observed and expected heterozygosities ranged from 0.0 to 0.8 and 0.0 to 0.6, respectively. Three of the loci in samples from Nigeria and Burkina Faso deviated significantly from Hardy-Weinberg Equilibrium (HWE), whereas no loci deviated significantly in samples from Niger. Analysis of molecular variance (AMOVA) indicated that 67.3% level of the genetic variation was within individuals compared to 17.3% among populations. A global estimate of FST=0.1 (ENA corrected FST=0.1) was significant (P⩽0.05) and corroborated by pairwise FST values that were significant among all possible comparisons. A significant correlation was predicted between genetic divergence and geographic distance between subpopulations (R2=0.6, P=0.04), and cluster analysis by the program STRUCTURE predicted that co-ancestry of genotypes were indicative of three distinct populations. The spatial genetic variance among M. vitrata in West Africa may be due to limited gene flow, south-north seasonal movement pattern or other reproductive barriers. This information is important for the cultural, chemical and biological control strategies for managing M. vitrata.

Control of cowpea insect pests has been almost entirely achieved through the use of chemicals by progressive farmers. However, the peasant farmer has traditionally tended to rely on chance and has often been unable to obtain yields that would be profitable. This paper examines the farmer's dilemma and the jrossibility of using host plant resistance (HPR) as an adjunct to other control methods in developing a sound integrated pest management of cowpea pests. The status of HPR in cowpea is reviewed with a view to identifying the areas where progress has been made with respect to the measurement and identification of resistance to formulate an effective integrated pest control program. The difficulties in achieving this are discussed in the light of our present data bank and the diversity of cowpea pests.

The trends in flowering, podding and seed yield of four cowpea varieties planted at different times of the growing season in 1975 and 1976, were studied along with the associated pest activity. Flowering, podding and seed yield were found to decrease over the season from April to September irrespective of whether the crop was protected against insect pests or not. However, there seemed to be two peak periods of pest activity—April to July and October to December—when severe damage to the crop occurred in unprotected plots. Planting in June or July usually led to an escape from several major pests even though the cool night temperatures and incidence of overcasts at that period seem to preclude optimal reproductive performance of the crop.

The pattern of insect pest succession on the crop over the season is discussed and it is suggested that for small farm holders in Southern Nigeria, who are unlikely to apply insecticides, planting in June is advisable.