Laboratory evaluation for pyrethroid resistance management against Spodoptera litura (Fab.)

Abstract

The study was undertaken to know the level of insecticide resistance in S. litura to selected pyrethroid insecticides and the role of herbal oils in mixture with pyrethroid insecticides against S. litura. Lambda cyhalothrin 5 EC was the most toxic compound against 3rd instar (F1) larvae of S. litura followed by cypermethrin 10 EC and fenvalerate 20 EC at lethal concentrations. Lambda cyhalothrin 5 EC + karanj oil @ 2% was found the most toxic mixture against 3rd instar (F1) larvae of S. litura than other pyrethroid-herbal oil mixtures tested. The F1 population of S. litura larvae were found more resistant (2.70 fold) to fenvalerate 20 EC followed by cypermethrin 10 EC (2.28 fold) and lambda cyhalothrin 5 EC (1.46 fold) over laboratory reared susceptible (F7) population of S. litura. Pyrethroid-herbal oil mixtures developed comparatively lower degree of resistance in F1 populations of S. litura when compared to relative resistance recorded for insecticides alone. The lowest relative resistance at LC50 level (i.e. 0.90 fold) was observed in case of lamda cyhalothrin 5 EC + karanj oil @ 2% mixture while highest (i.e. 2.50 fold) was in case of fenvalerate 20 EC + sesame oil @ 2%. Karanj oil used in mixture with pyrethroids was most effective on suppression of resistance in S. litura followed by neem oil and sesame oil. Among the treatments, maximum suppression of resistance (i.e. 46.67%) was observed in fenvalerate 20 EC + karanj oil @ 2% and minimum (i.e. 6.58%) in cypermethrin 10 EC + sesame oil @ 2%.