Sterol demethylation inhibitor fungicides as disruptors of insect development and inducers of glutathione S-transferase activities in Mamestra brassicae.

To study physiological and biochemical effects of demethylation inhibitor (DMI) fungicides on non-target insects, larvae of the cabbage moth, Mamestra brassicae L., were exposed orally to propiconazole, (R,S)-1-[2-(2,4-diclophenyl)-4-propyl-1,3-dioolan-2-ylmetyl]-1H-1,2,4-triazole (100, 200 and 600 mg L(-1)) and fenpropimorph, (+/-)-cis-4-[3-(4-tert-butylphenyl)-2-methylpropyl] 2,6-dimethylmorpholinc (10, 100, 200 and 600 mg L(-1)) in a semi-synthetic diet. Ten mg L(-1) of fenpropimorph reduced larval weight and induced in vitro glutathione S-transferase activity. Reduced larval and pupal growth rate, reduced survival, prolonged developmental time, and altered patterns of larval survival and adult emergence were found for one or both fungicides in at least one of the concentrations tested. The results suggest, that although the use of agricultural fungicides is generally regarded as of minor ecotoxicological consequence for insects, feeding on DMI-treated crops may influence insect fitness, and may also leave them susceptible to pesticide treatments or to residues of pesticides and other pollutants in their food. Standard methods to detect such effects should be developed for use in the environmental risk assessment of these products.