Optimum chilli density inter-planted with maize in relation to aphid population and incidence of virus diseases on chilli

The study was conducted to determine the most effective chilli density inter-planted with maize to reduce the population of the aphid, Aphis gossypii and incidence of virus diseases on chilli. The treatments were MCMCMCM, MCCMCCM, MCCCCCM and CCCCCCC (M, Maize; C, Chilli). Results showed that the number of alate aphids caught per day and number of apterous aphid per plant was significantly different among treatments (P less than 0.05). The number of apterous aphid per plant was found to be higher in plots where higher number of chilli plants were inter-planted with maize. However, there were no significant differences (P greater than 0.05) in the number of apterous aphid in treatments of MCMCMCM and MCCMCCM or in treatment of MCCCCCM and CCCCCCC. The number of apterous aphids per plant and counts of alate aphids per treatment were significantly (P less than 0.05) more abundant in the monoculture plots than in other treatments. The number of apterous aphids was also found to be significantly different (P = 0.001) at different level of strata. The numbers were higher in lower than in upper stratum. Results showed that there was a significant correlation (r = 0.96, P less than 0.05) between percent virus diseases and treatments, days after transplanting (DAT) and numbers of apterous and alate aphids. Incidence of virus diseases was only correlated with treatments and DAT after subjected to a stepwise elimination regression analysis. This suggests that the incidence of virus diseases were influenced by the number of chilli plants inter-planted with maize and duration of chilli plants exposed in the field. The cumulative percent of cucumber mosaic virus (CMV) incidence was significantly lower (P = 0.001) than chilli veinal mottle virus (CVMV) in all the treatments. However, there was no significant difference (P greater than 0.05) in the percent of CVMV incidence among the treatments. It was found that percent virus disease incidence significantly correlated (r = 0.45) with the rainfall. Result of this study suggests that the chilli-maize inter- cropping system of MCCMCCM could reduce the population of aphid and hence incidence of virus diseases on chilli.