Effects of plant height, maturity and climatic factors on the population of whitefly (Bemisia tabaci) on chilli (Capsicum annuum L.)

The effects of plant height, plant maturity and climatic factors namely, sunshine duration (h/d), wind speed (km/h), rainfall amount (mm/d) and relative humidity (%) on the population abundance of whitefly (WF), Bemisia tabaci on chilli were determined. The adult WF preferred leaves at the upper stratum than at the middle and lower strata (p 0 .05). The number of adult WF per plant was significantly higher (p 0.05) at 77 days after transplanting (DAT) than other sampling dates, while the immature WF (larvae and pupae) were significantly higher (p 0.05) at 112 DAT compared to other sampling dates. The lowest numbers of adult and immature WF stages were recorded at 7 DAT. There was a positive correlation (r = 0.757, F =17.69, df = 1 14, p = 0.001) between number of adult WF and immature stages per plant at each sampling date. Positive correlation was also obtained between numbers of adult (r = 0.747, F = 17.69, df = 1 14, p = 0.001) and immature WF per plant and plant height (r = 0.965, F = 186.78, df = 1 14, p = 0.0001). The number of adult (r = 0.743, F = 17.29, df = 1 14, p = 0.001) and immature (r = 0.964, F = 184.42, df = 1 14, p = 0.0001) WF per plant had a strong and positive correlation with the plant maturity. Whereas sunshine duration, wind speed, rainfall amount and relative humidity had no correlation with the abundance of adult and immature WF throughout the cropping period. The results suggested that control of WF should be taken immediately after the transplanting of chilli.