Effects of watering regimes on aphid infestation and performance of selected varieties of cowpea (Vigna unguiculata L. Walp) in a humid rainforest zone of Nigeria
Department of Crop, Soil and Pest Management, Federal University of Technology, PMB 704, Akure, Nigeria
Host plant drought stress affects plant productivity (growth and reproduction) and insect performance. This study was conducted to determine whether resistance to one major cowpea insect pest (Aphis craccivora, Koch) in identified cowpea varieties holds under different soil moisture regimes in the dry season period in a humid tropical rainforest zone. This information is basic to the use of insect resistant varieties for agricultural development under marginal conditions. Treatments consisted of factorial combinations of three water application regimes by four cowpea varieties grown in drainage lysimeters installed on the field in the dry season period in Akure, rainforest zone of Nigeria. Two aphid susceptible (Ife brown and Vita 7) and two aphid resistant (IT845-2246 and IT835-728-5) varieties were compared under soil moisture regimes. Reduction in the amount of water available to the cowpea plant (soil moisture deficit stress) in the host plant affected population trends of aphids in the different growth stages of cowpea. There were significant variations among tested aphid susceptible and aphid resistant cowpea varieties on aphid survival, population density (colony size), damage levels and seed yield reductions in relation to soil moisture regimes. A significantly lower number of aphids was observed in the resistant varieties than in the susceptible varieties. Significant interactions between watering regimes and varieties were found for aphid survival rates, biomass and fruit yields in this study. The resistant varieties supported significantly lower aphid survival rates compared with susceptible varieties. Significant negative linear correlations were found for watering intervals (regimes) and aphid population, shoot biomass and seed (grain) yield. © 2005 Elsevier Ltd. All rights reserved.
aphid; drought stress; host plant; pest resistance; trend analysis; Africa; Eastern Hemisphere; Nigeria; Sub-Saharan Africa; West Africa; World; Aphididae; Aphis craccivora; Insecta; Vigna unguiculata