K. D. Wing, Matthew D. Sacher, Yasushi Kagaya
Sep 12, 2000
Citations
13
Influential Citations
257
Citations
Quality indicators
Journal
Crop Protection
Abstract
Abstract DPX-MP062 (indoxacarb) is a novel oxadiazine insecticide which has good field activity against a number of pest Lepidoptera, as well as certain Homoptera and Coleoptera. Indoxacarb (discovered and developed by E.I. DuPont and Co.) is a 75%S : 25%R mixture of enantiomers at the chiral bicyclic carbon; DPX-JW062 is the corresponding racemic compound. Several species of lepidopteran larvae can rapidly metabolize 14 C-JW062 to 14 C-DCJW (for N-decarbomethoxyllated JW062) after ingestion, and more slowly after topical treatment; this conversion is correlated with the appearance of neurotoxic symptoms. Several sucking insects are also capable of absorbing and bioactivating indoxacarb after either dermal or oral administration, but do so much more slowly than the Lepidoptera. DCJW is a highly potent, voltage-dependent blocker of Na + -dependent compound action potentials when tested in a Manduca sexta larval abdominal motoneuron preparation; DPX-JW062 was much less potent in this regard. When larvae were poisoned in vivo, onset of paralysis and block of central nervous system action potentials was more rapid with DCJW than with DPX-JW062; onset of neurotoxic symptoms leads to a rapid and irreversible halt in feeding. The S-enantiomer of DCJW is active both in the motoneuron preparation in vitro and in lepidopteran larvae in vivo; however S-DPX-JW062 is active in vivo only, while the R-enantiomers of DCJW and DPX-MP062 are inactive in both. Thus, activation of the parent oxadiazines to the S-enantiomers of the N -decarbomethoxyllated metabolites, which are powerful sodium channel blockers, is the toxic mechanism of action in Lepidoptera and apparently for other pest insects as well; however, the rate of bioactivation is a critical factor in determining the speed and ultimate toxicity of this compound in different insect species. Indoxacarb's inherent activity against Lepidoptera is comparable to the most potent insecticides ever commercialized.