Abstract:

【Objective】 In this paper, the relationship of the resistance of the common cutworm, Spodoptera litura Fabricius, to lambda-cyhalothrin and cuticular penetration of lambda-cyhalothrin was studied. 【Method】 Topical application, leaf-dipping and leaf-sandwich methods were used to determine the resistance levels of Spodoptera litura to lambda-cyhalothrin and cuticular penetration of 14C-lambda-cyhalothrin was carried out. 【Result】 The results indicate that the sequence of resistance levels of the 3rd instar larvae was topical application (2765.4 fold) ＞leaf-dipping method (365.1 fold) ＞leaf-sandwich method (34.0 fold) and the sequence of resistance levels of the 5th instar larvae was also topical application (2271.3 fold) ＞leaf-dipping method (257.2 fold) ＞leaf-sandwich method (20.2 fold). The resistance levels of the 3rd instar larvae were 81.3 and 10.7 times higher obtained by topical application (contact toxicity) and leaf-dipping method (contact toxicity and stomach toxicity) than that by leaf-sandwich method (stomach toxicity). Compared in the same way, the resistance levels of the 5th instar larvae were 112.4 and 12.7 times higher. Therefore, the resistant population of Spodoptera litura has a resistance level obtained by way of contact toxicity at least 81.3 times than that of stomach toxicity. After 0.5 h and 1.0 h treatments, the results indicate that there was no significant difference of cuticular penetration of 14C-lambda-cyhalothrin between the resistant and susceptible populations. After 2 h treatment, the rate of cuticular penetration of the resistant population became a little slower than that of the susceptible population. After 8h treatment, the rate of cuticular penetration in 3rd and 5th instar larvae of the resistant population was about 0.77 and 0.67 folds of that in the susceptible population. 【Conclusion】 Delayed cuticular penetration is responsible for the resistance of Spodoptera litura to lambda-cyhalothrin.

Key words: Spodoptera litura')">Spodoptera litura, insecticide resistance, lambda-cyhalothrin, cuticular penetration