Abstract
Field studies on the effect of bio-pesticides against Amrasca devastans and Bemisia tabaci on okra were carried out at the University of Karachi. Seeds of Abelmoschus esculentus L. (Okra) were planted on March 2011 in a randomized complete block design with 4 replications. Treatment applied were T1 (Neem Powder Azadirachta indica), T2 (Heeng, Asafotida), T3 (Tobacco Nicotiana tabacum extract), T4 (Detergent, as the least toxic compound for comparison) and T5 (untreated control). The pretreatment observations were recorded at 24 h before spray, whereas, post-treatment observations were carried out after 24, 48, 72 hrs and at one week intervals. The crop was sprayed twice during the experimental period. The results revealed that bio-pesticides reduced the population of B. tabaci and A. devastans up to one week interval. Maximum reductions in population of both the insects were recorded during both sprays. The means showed that Tobacco Nicotiana tabacum extract reduced population of B. tabaci up to 0.29 per leaf, (92.62%) followed by Neem powder Azadirachta indica 0.33 (91.50%) Heeng Asafoetida 1.83 (50.93%) and detergent 1.85 (53.16%) and A. devastans up to 0.04 (99.57%), 0.14 (98.18%) 3.17 (59.89 %) and 3.18 (59.64%) respectively. Similarly, in second spray the population of B. tabaci was reduced up to 1.87 (89.39%). 2.74 (84.04%), 5.88 (65.89 %) and 6.44 (63.49%) percent by Azadirachta indica power, Nicotiana tabacum extract, Asafoetida and Detergent, respectively. The population of A. devastans was reduced by these agents up to 0.33 (96.09%), 0.39 (95.41%), 3.37 (9.08%) and 3.40 (62.34%) respectively. Analysis of variance showed significant difference in the effectiveness of the biopesticides. However, LSD showed non-significant difference between 72 h in Azadirachta indica powder and Nicotiana tabacum extract, Asafoetida and Detergent. It is concluded that the bio-pesticides from Azadirachta indica, Nicotiana tabacum and Asafoetida are safer, easy and cheap.
