CORRELATION ANALYSIS BETWEEN DAMAGE PARAMETERS AND COWPEA YIELD DUE TO POST-FLOWERING INSECT PEST IN KATSINA, SADANO-SAHELIAN ECOLOGY, NIGERIA

Abstract

Damage indices and yield potential of cowpea were compared in a field trial consisting of intra-row spacings, sowing dates, and pesticides as a combination of Integrated Pest Management (IPM) on a complex of pod-sucking bugs (CPSBs) and cowpea pod-borer populations. The trial was carried out during the rainy seasons of 2015 and 2016 in Katsina, with a sudano-sahelian ecology. The trial aims to compare the relationship between yield and CPSB damage indices. The experiment was laid out using a split-split plot design with intra-row spacings (SP₁-75 × 20 cm, SP₂-75 × 30 cm, and SP₃-75 × 40 cm) allocated to the main plot, sowing dates (SD1-2 July; SD2-23 July, and SD3-13 Aug.) to the sub-plot, and the sub-sub-plots were allocated to pesticides (neem kernel seed extract (NKE), Maruca vitrata Multi-Nucleopolyhedrosis (MaviMNPV) viral suspension, synthetic insecticide (Cyper diforce), and a control. The treatments were randomized and replicated three times. Data were measured on damage parameters caused by a complex of pod-sucking bugs (CPSBs) and legume pod borer, Maruca vitrata. The data were correlated using the Pearson Correlation Coefficient for a Two-tailed test with df = (N-2) at *P≤0.05 (r = 0.250) and **P≤0.01 (r = 0.325) using SAS software. The combined interaction results indicated that a significant and positive correlation (r>0) exists between the post-spray population of M. vitrata and the post-spray flower damage 10 WAS, respectively (0.766**). Similarly, percentage (%) M. vitrata population in cowpea pods was positively and highly related to % cowpea damage by M. vitrata 10 WAS, respectively (0.751**). Yield was, however, negatively (r<0) and weakly related to percentage cowpea damage by CPSBs at harvest (-0.420**) and % grain damage by M. vitrata in 300 g (-0.265*). It is therefore recommended that, for successful, high-yield cowpea in the study area and similar ecologies, synchronized sowing and the application of control measures should be initiated early, before the critical cowpea reproductive phase, to reduce infestation and improve yield.