Abstract: The cytotoxicities of 19 kinds of fungicides against Spodoptera litura (SL) cells were studied by using MTT method. The results showed that thiram, diniconazole, hexaconazole, flusilazone, benalaxyl, difenoconazole, tebuconazole and myclobutanil possessed high toxicity against SL cells. The LC₅₀ values of myclobutanil, diniconazole, hexaconazole and tebuconazole, which belong to triazoles fungicides, at 48 h after treatment were 21.94 μg/mL, 23.80 μg/mL, 33.16 μg/mL and 47.63 μg/mL, respectively. Effect of myclobutanil on the protein content and the leakage rate of lactate dehydrogenase (LDH) of SL cells were studied by using colorimetric method of Coomassie brilliant blue G₂₅₀. The reduced rates of protein content of SL cells treated with myclobutanil at concentration of 20 μg/mL for 12 h, 24 h, 48 h and 72 h were 8.55%, 25.95%, 42.95% and 67.05%, respectively. The leakage rates of LDH of SL cells treated with myclobutanil at concentration of 20 μg/mL for 24 h and 48 h were 30.66% and 32.05%, respectively. Triazoles fungicides could decrease the larvae weight of S. litura obviously. The reduced rates of blood corpuscles of the 4th-instar larvae of S. litura treated with myclobutanil at dose of 0.5 μg/larva, 1.0 μg/larva and 2.0 μg/larva by the inject method for 72 h were 12.31%, 25.96% and 25.73%, respectively. The LD₅₀ values of myclobutanil injected into S. litura larvae at 48 h and 72 h after treatment were 1.59 μg/larva and 1.53 μg/larva, respectively. The results suggest that it possesses good research potential that looking for new leading compounds for insecticides from fungicides with vitro cultured cells as object.

Key words: Spodoptera litura, fungicide, myclobutanil, SL cell line, cytotoxicity