Seasonal abundance of Oleander aphid, Aphis nerii Boyer de Fonscolombe and its predator on Gymnema sylvestre (R.Br) in relation to weather parameters from India

India has a rich source of biodiversity of medicinal plants, which serves as a source of livelihood for a large Indian population. For the past several decades, most of the research works on medicinal plants have been focused on isolating their active ingredient and preparing a suitable commercial formulation while completely neglecting their conservation. Very few studies have been done to understand the factors, especially biotic ones that limit the yield of medicinal plants. Therefore, the present study aims at studying the nature of the damage, severity of the injury, and population dynamics of Aphis nerii and its natural enemy ( Cheilomenes sexmaculata ) on madhunashini, Gymnema sylvestre at ICAR-Directorate of Medicinal and Aromatic Plants Research, Anand (Gujarat) India along with the study of weather parameters affecting pest population during two years from 2018–20. The percent incidence and severity of A. nerii ranged from 0 to 100 percent and 0 to 4, respectively. The peak population (275.56 and 293.31/10 cm twig) was recorded at the 6 th SMW (Standard Meteorological Week) in both the observed years. The occurrence of C . sexmaculata started during the first fortnight of November, and peak population was recorded during the 6 th SMW. During the study period, the aphid population was negatively correlated with all the density-independent factors. The different concentrations of neem oil (10000 ppm) like 0.25, 0.50, and 0.75 percent were used to test the efficacy during the peak insect activity period. Our study suggests that neem oil spray (10000 ppm) @ 0.75 percent could effectively manage the aphid population in field conditions.