Effect of Thai neem extracts from KU-pilot plant and neem oil for the control of whitefly (Bemisia tabaci) on tomato
1999
Kwanchai Sombatsiri (Kasetsart Univ., Bangkok (Thailand). Faculty of Agriculture. Dept. of Entomology)
Efficacy test of Thai neem extracts in different forms; neem seed extract (NSE), neem fruit extract (NFE), the mixture of NSE+NFE and neem oil (NO) from KU Pilot plant on whitefly (Bemisia tabaci) was conducted in laboratory and field condition. The results were : Contact poision study : the mixture of NSE+NFE (aza 0.295 percent) and No showed the highest efficacy on egg mortality resulting in lower LC50 = 0.2 and 0.27 percent, respectively. The lower efficacy was NFE (aza 0.09 percent) and NSE (aza 0.5 percent) by LC50 = 0.68 and 0.82 percent, respectively. In the same result the mixture of NSE+NFE and NO caused high larval mortality showing LC50 = 0.25 and 0.1 percent, respectively. The lower efficacy was NFE and NSE by LC50 = 0.72 and 1.02 percent, respectively. For the next testing on adult, NSE+NFE, NO and NSE caused the similarily effective by LC50 = 0.15, 0.18 and 0.16 percent, respectively, followed by NFE with LC50 = 0.52 percent Stomach poison study : All four neem formulations showed the high efficacy causing death rate of whitefly adult between 80-100 percent Antioviposition effect : NSE, NSE+NFE and neem oil caused the almost similarity in being the oviposition deterrence of the whitefly. The average number of egg-laying in all test material was 4.5, 5.0, 6.5 and 10.0 comparing with untreated control as 17.8, respectively. For field experiment, it has been found that NSE, NSE+NFE and neem oil could reduce the amount of whitefly adult as that of synthetic insecticide, carbosulfan with no statistical difference.
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