Efficacy of different biorational insecticides against Aphis nerii Boyer de Fonscolombe (Hemiptera. Aphididae) on Gymnema sylvestre (R.Br) under laboratory and field conditions

Gymnema sylvestre, a perennial woody climber popular for its antidiabetic property and its leaves are widely recommended to use in the traditional system of medicine. The oleander aphid, Aphis nerii is a major pest of G. sylvestre from October to March in central India. The present study was carried out to evaluate the efficacy of different biorational insecticides like Azadiractin 1% EC (10,000 ppm), aqueous leaf extract (5%) of Kalmegh or the Creat, King of Bitters (Andrographis paniculata) and Indian bael or Golden apple (Aegle marmelos), insect growth regulator (Buprofezin 25% SC), commercial entomopathogenic formulations like Beauveria bassiana (2 ×10⁹ spores/ml), Metarhizium anisopliae (2 × 10⁹ spores/ml), Lecanicillium muscarium (Verticillium lecanii; 2 × 10⁹ spores/ml) on A. nerii under laboratory and field condition during 2019 and 2020. It was discovered that the leaf spray method was superior to the leaf dipping method. In the leaf spray method, hundred percent mortality of A. nerii was recorded with the application of azadirachtin post 72 HAT and efficacy of B. bassiana, M. anisopliae and L. muscarium were statistically in the same group during both year of study. However, in the leaf dip method, hundred percent mortality of A. nerii was recorded with the treatment of azadirachtin post 96 HAR. In both bioassay methods, the lowest population reduction and mortality were observed in bael followed by kalmegh plant extract under laboratory conditions. On the tenth days of treatment, azadirachtin showed hundred percent reduction in the aphid population with hundred percent efficacy. The entomopathogenic fungi like M. anisopliae (85.4%, 87.8%) and B. bassiana (78.3%, 83.8%) were equally effective in reducing A. nerii population with the efficacy of (87.4%, 90.4%) and (81.2%, 87.2%) under field condition during 2019 and 2020 respectively.