Journal of Taiwan Agricultural Research

Author:Edward Y. Cheng, Ching-Hua Kao* and Yu-Bing Hwang

Abstract:

    Abamectin is the first microbial insecticide extracted from Streptomyces avermitilis and has been registered for diamondback moth control. Not long after abamectin was registered, the generic products of abamectin started to market, and the low-cost, un-refined generic products soon out-competed the registered abamectin by a volume of more than 9 to 1. This forced abamectin being withdrawn from its registration in 2001. Currently, the generic products have occupied the whole market without detailed chemical composition and toxicological information. In this study, we had collected 23 samples of generic products for components/composition analysis and compared those data with the standard abamectin on five aspects: (1) total avermectin content, (2) the B1 composition, (3) the ratios of B1a/B1b, (4) contents of avermectins, and (5) the avermectin composition spectrum. The results indicated the total avermectins of generic products is 2 to 6 times of the registered abamectin, but the generic products contained only two-thirds of registered B1. More than 81% of total avermectins in generic products are unregistered components i.e., A1a, A1b, A2a and B2a. The toxic components of generic products varied greatly from sample to sample. Only the averaged ratio of B1a/B1b is the same as abamectin, however, this ratio was also sample-dependent, which varied from 90:10 to 100:0. The biggest problem of generic products is the amount of their toxic impurity content is about 5.37%, that is 134 times higher than the legal limit. The result confirmed that the generic products are crude, low-cost and unrefined pesticides, which lack toxicological information and post possible health hazard of unregistered toxic residues on vegetables. The generic products of abamectin induced high resistance in the diamondback moth within five years and the resistance ratio had reached 2500- to 5000-fold in 2001. These generic products also cause significant problem for pesticide registration, regulation and application, which should be reevaluated and corrected.

Key words:Abamectin, Generic product, Impurities, Analysis, Pesticide regulation

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