Spacio-temporal dynamics of insecticide resistance in leafhoppers Amrasca biguttula biguttula (Ishida) (Homoptera: Cicadellidae) in cotton
Phulse VB and Udikeri SS
In the present study, insecticide resistance acquired by leafhoppers Amrasca biguttula biguttula in cotton was assessed through bioassay for populations of Hanumanamatti, Dharwad and Annigeri in Karnataka. Among different insecticides a high degree of resistance was shown against neonicotinoids compared to organophosphates.Similarly resistance was relatively in Hanumanamatti population than Dharwad and less in Annigeri. The highest resistance of 0.25 ml/l as LC50 was observed against Imidacloprid 17.8 SL in Hanumanamatti population which is equal to recommended dosage. The LC50 for thiomethoxam was 0.27 ml /l which is higher than its recommended dosage. Leafhoppers responded better to selected organophosphates particularly to acephate with LC50 of 0.53 g / l. The resistance noticed against fipronil was least. At Dharwad and Annigeri locations LC50 values varied from (0.45 to 0.53 ml/l) and (0.42 to 0.49 ml/l) with seasonal mean LC50 values of 0.47 and 0.45 ml/l compared to recommended dosages 1.0 ml/l with respect to fipronil compared to LC50 0.46 to 0.56 ml/l in LC50 Hanumanamatti population across season.