Population Dynamics and Damage by Pod-Sucking Bugs under Integrated Pest Management Strategies in Cowpea (<i>Vigna unguiculata</i> L. Walp.) in the Sudan Savanna of Nigeria

Abstract

Insect pests remain a major production bottleneck, particularly those that infest the crop during the post-flowering stage. Pod-sucking bug complexes can inflict severe damage on cowpea productivity if unchecked. A field trial consisting of intra-row spacings, sowing dates, and pesticides as a combination of Integrated Pest Management (IPM) was carried out on a complex of pod sucking bugs (CPSBs) population during the rainy seasons of 2015 and 2016, respectively, in Katsina. The experiment was laid out using a split-split plot design, with intra-row spacing allocated to the main plot, sowing dates to the sub-plot, and the sub-sub-plots allocated to pesticides. NKE powder was used at the rate of 5 kg ha⁻¹, mixed with 2 kg ha⁻¹ bar soap as an emulsifier. The viral suspension was diluted to a concentration of 7.57 × 10¹¹ and applied at 106 ml in 115 L of water per hectare. The synthetic insecticide containing cypermethrin (30 g L⁻¹) and dimethoate (250 g L⁻¹) was applied at 1.5 L ha⁻¹ using a CP-3 knapsack sprayer. The treatments were randomized and replicated three times. Data collected were measured on the CPSB population and final cowpea grain yield, which were subjected to analysis of variance, and means were separated using LSD at 5%. The result showed that varying cowpea sowing from 2nd July (1.29) to 13th Aug. (1.23) significantly (P≤ .05) reduced CPSBs, with its peak population occurring on cowpea sown on 23rd July (1.48), respectively, in all the sampling weeks. Use of MaviMNPV (1.30), neem (1.26), and cyper diforce (1.25) significantly reduced CPSBs population compared with the control (1.50). However, synthetic insecticidess recorded lower CPSB but were comparable to other control options. The result of the combined interaction showed that varying sowing to 23rd July and using cyper diforce produced the lowest effect (1.22) CPSB per plot. The result of the use of pesticides showed that, significantly (P≤ .05), the highest grain yield per hectare was recorded in the combine interaction of varying sowing to 13th Aug. + insecticidal spray (631.49 kg ha-1). Therefore, it is concluded that CPSB damage on cowpea is directly proportionate to their numbers. It is recommended that varying cowpea sowing and the use of pesticides will reduce CPSB populations on cowpea and, consequently, reduce cowpea damage in the study area.