CORRELATION OF PERFORMANCE OF SOLE-CROP AND INTERCROP COWPEAS WITH AND WITHOUT PROTECTION FROM INSECT PESTS

Five field trials were conducted in Kenya with 12 or 16 diverse cowpea genotypes grown as sole-crops and as intercrops, simultaneously with early-maturing maize and with and without insect protection (in four of the five trials). Objectives were to (1) determine the adequacy of protected or unprotected sole-crop evaluations of genotypes for unprotected intercrop farming systems, and (2) determine if specific plant growth habits or growth durations are advantageous under intercropping. Protected sole-crop yields were not correlated with unprotected intercrop yields in any of the four experiments, but unprotected sole-crop yields were consistently positively correlated with unprotected intercrop yields, and were significant in three of five trials. Differences in field tolerance to insect pests among the lines partially accounted for these correlations. Significant or highly significant positive correlations were observed between protected sole-crop and protected intercrop yields in three of four trials. While protected sole-crop evaluations would be useful in identifying lines for a protected intercrop farming system, such procedures would fail to identify lines best suited to unprotected intercrop systems used by the majority of farmers. Early generation nurseries could be conducted using unprotected sole-crops to evaluate tolerance to pests, but final evaluations should be conducted with the unprotected intercropping system practiced by most farmers. No particular growth habit or developmental pattern appeared to be particularly advantageous under the intercropping system investigated.