Gy. Zhao et al., MECHANISMS ASSOCIATED WITH DIAZINON RESISTANCE IN WESTERN FLOWER THRIPS, Pesticide biochemistry and physiology, 49(1), 1994, pp. 13-23
Mechanisms of resistance were examined using UMC and KCM western flowe
r thrips, Frankliniella occidentalis (Pergande), that differed in thei
r susceptibility to diazinon by 14.2 times, with the latter strain bei
ng more tolerant. Diazinon penetration, metabolism, and excretion were
faster in KCM than in UMC thrips. Metabolism of diazinon in both stra
ins was mainly oxidative, and major metabolites cochromatographed with
diazoxon, 2-isopropyl-4-methyl-6-hydroxypyrimidine, and '-hydroxy-2'-
propyl)-4-methyl-6-hydroxypyrimidine. Carboxylesterase activity in KCM
thrips was significantly lower than that in UMC thrips and was 9.6 an
d 20.4 times less sensitive to diazoxon and eserine, respectively. Ace
tylcholinesterase (AChE) activity in KCM and UMC thrips was similar, b
ut that in KCM thrips was 9.6 times less sensitive to diazoxon. Butyry
lcholinesterase (BuChE) activity in the two strains was similar and wa
s appreciably higher than AChE activity. BuChE activity in KCM thrips
was 170 times less sensitive to diazoxon than that in UMC thrips. No i
nterstrain difference in glutathione S-transferase activity was observ
ed with 1-chloro-2,4-dinitrobenzene as substrate. Diazinon resistance
in western flower thrips was due chiefly to rapid metabolism and insen
sitive AChE. The role of BuChE, if any, in diazinon resistance is not
currently known; however, by serving as an alternate phosphorylation s
ite, it could reduce the level of organophosphate at the AChE target i
n both strains. (C) 1994 Academic Press, Inc.