Glucosinolate breakdown products as insect fumigants and their effect on carbon dioxide emission of insects

BACKGROUND: Glucosinolate breakdown products are volatile, therefore good candidates for insect fumigants. However, although they are insecticidal, the mode of action of such natural products is not clear. We studied the insecticidal effect of these compounds as fumigants, and monitored the production of carbon dioxide by the insects as a probe to the understanding of their mode of action. RESULTS: The fumigation 24-h LC(50) against the house fly (Musca domestica L.) of allyl thiocyanate, allyl isothiocyanate, allyl cyanide, and l-cyano-2-hydroxy-3-butene was 0.1, 0.13, 3.66, and 6.2 μg cm(-3), respectively; they were 0.55, 1.57, 2.8, and > 19.60 μg cm(-3), respectively, against the lesser grain borer (Rhyzopertha dominica Fabricius). The fumigation toxicity of some of the glucosinolate products was very close to or better than that of the commercial insect fumigants such as chloropicrin (LC(50): 0.08 and 1.3 μg cm(-3) against M. domestica and R. dominica, respectively) and dichlorovos (LC(50): < 0.02 and 0.29 μg cm(-3) against M. domestica and R. dominica, respectively) in our laboratory tests. Significantly increased CO(2) expiration was found in insects exposed to the vapor of allyl isothiocyanate, allyl thiocyanate and allyl isocyanate. Allyl isothiocyanate was also found to increase the CO(2) expiration of the American cockroach (Periplaneta americana L.). CONCLUSIONS: Glucosinolate breakdown products have potential as biodegradable and safe insect fumigants. They may act on the insect respiratory system in their mode of action.