Potential impact of intercropping on major cowpea field pests in Uganda

Insect pests are perhaps the most important constraint to cowpea (Vigna unguiculata L. Walp) production. In Uganda, aphids, thrips, pod sucking bugs and pod borers are ubiquitous and very devastating, sometimes leading to total crop failure. On-farm studies were conducted at 3 sites in eastern Uganda for three consective seasons to evaluate the use of intercropping as a pest control strategy in cowpea. Two local cowpea cultivars, Ebelat (Erect) and Icirikukwai (spreading) were grown as sole crops or intercropped with a local variety of greengram (Vigna radiata ) or sorghum Sorghum bicolor cv. Seredo. Aphids and thrips populations were significantly reduced in the cowpea + sorghum intercrop but were higher in the cowpea + greengram intercrop. In contrast, pod borer and pod sucking bug infestations and their associated damage were significantly higher in the cowpea + sorghum intercrop than in the other cropping systems. These results contradict previous reports and indicate that (a) not all pests are controlled by intercropping, (b) to be effective, intercropping has to be part of a pest management system that involves other control strategies, and (c) choice of a cropping system for IPM should consider the pest profile