HOST PREFERENCE AND MANAGEMENT OF WHITEFLY, BEMISIS TABACI GENN. ON OKRA

Abstract

An experiment was conducted in the field of Sher-e-Bangla Agricultural University, Dhaka during March to July. 2007 to explore the resistance source(s) among four okra varieties/genotypes against whitefly. Lk',nisia tabaci Genn. as well as to evaluate the effectiveness of some selected management practices in controlling whitefly as well as Okra wi/ow vein cleari'zg mosaic virus (OLYVCMV) on okra. Out of four okra varieties. Hybrid Dherosh performed as highly resistant in respect of incidence of adult whitefly ()6.34 adults/S plants), OkYVCMV infected leaves (1.20%) and plants (9.60%). The two varieties RU Dherosh 1 (28.93 adults/S plants. 4.39% leaf infection and 15.20% plant infection, respectively) and BARI Dherosh 1(31.33 adults/S plants. 5.69% leaf infection and 21.40% plant infection, respectively) pertbrmed as resistant and the variety Choice Dherosh rated as highly susceptible host (67.60 adults/5 plants. 16.96% leaf infection and 74.40% plant infection, respectively). The incidence of adult whitefly was highly significant and positively correlated to the incidence of both OLYVCMV infected leaves and plants of okra. The resistant variety Hybrid Dherosh produced maximum number of fruit per plant (14.33) and single fruit weight (16.97 gm) as well as the highest yield (7210.3 kg/ha) as compared with the highly susceptible variety Choice Dherosh. which produced minimum number of fruit per plant (8.40) and single fruit weight (12.17 gm) as well as the lowest yield (3380.60 kg/ha). The incidence of OkYVCMV infected plants was negatively correlated to the yield of okra varieties. Among five different management practices applied against whitefly on okra. T1 (spraying of Admire 200 SI.. [Imidacloprid] 2I' 0.2 mI/titer of water at 7 days interval) performed as best in reducing 79.63% adult whitefly incidence. 76.65% OkY\'CMV infected leaves and 87.59% plant infection over control. Spraying of Admire 200 SI, 2i 0.2 mI/liter of water also performed as best in increasing 109.65% yield over control as well as other yield attributes such as height of plant, number of branch per plant, number of fruit per plant. Considering the economic analysis of the different management practices, 14 (spraying of neem oil @J 3% at 7 days interval) considered as the most profitable treatment in respect of BCR (9.23), which was ceo-friendly also. But in terms of national demand. Ti (spraying of Admire 200 5Th (5 0.2 mI/liter of water at 7 days interval) was the most effective treatment, which enhanced to produce maximum yield (7048.83 kg/ha) and contributed reasonable 8CR (4.59).