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Field resistance of Spodoptera litura (Fab.) to conventional insecticides in India

B, Kiran Gandhi, Patil, R.H., Y, Srujana
Crop protection 2016 v.88 pp. 103-108
Spodoptera litura, at-risk population, chlorpyrifos, insecticide resistance, lambda-cyhalothrin, larvae, lethal concentration 50, pesticide application, soybeans, India
The present study was carried out to evaluate conventional insecticide resistance in populations of Spodoptera litura (Fab.) from seven different soybean-growing districts (Dharwad. Belgaum, Pune, Parbani, Adilabad, Hyderabad and Indore) of India. Experimental results revealed among the three chemical insecticides bioassayed, quinolphos 25 EC registered the highest LC50 value (29.7 mg a.i./L) followed by chlorpyrifos 20 EC (18.3 mg a.i./L) while the lowest LC50 value was found for lambda-cyhalothrin 5 EC (1.3 mg a.i./L) in a susceptible population of S. litura larvae. Evaluation of the seven different populations of S. litura from India showed that populations from Adilabad and Pune exhibited elevated LC50 values for chlorpyrifos [(1622.0 mg a.i./L) and (1137.0 mg a.i./L)], quinolphos [(1892.0 mg a.i./L) and (1744.0 mg a.i./L)] and lambda-cyhalothrin [(56.4 mg a.i./L) and (41.6 mg a.i./L)], respectively. Seven different S. litura populations collected varied in their resistance ratio (RR) for three conventional insecticides used in this study. For chlorpyrifos RR values ranged from 3 to 88 fold, for quinolphos RR values ranged from 3 to 63 fold and for lambda-cyhalothrin RR values ranged from 2 to 42 fold in the seven different S. litura populations compared to the susceptible population. Based on the raised LC50 values, the resistance is quite concerning for organophosphates (chlorpyrifos and quinolphos). The present study is a warning bell suggesting the cautious use of organophosphates and lambda-cyhalothrin in soybean.