Population dynamics of major insect pest of green gram (Vigna radiata L.) and bio-pesticidal management of spotted pod borer [(Maruca vitrata) Fabricius]

Abstract

The present study entitled “Population Dynamics of Major Insect Pests of Green Gram (Vigna radiata L.) and Bio-pesticidal management of Spotted Pod Borer [(Maruca vitrata) Fabricius]” was conducted during the Kharif season of 2024 at the Organic Research Farm, Karguan ji, Department of Entomology, Institute of Agricultural Sciences, Bundelkhand University, Jhansi (U.P.). The investigation aimed to study the seasonal population dynamics of major insect pests of green gram, evaluate the efficacy of different bio-pesticides against the spotted pod borer (Maruca vitrata), and determine the economic feasibility of bio-based pest control methods. The experiment was laid out in a Randomized Block Design (RBD) with eight treatments and one untreated control; each replicated three times. Treatments included Neem oil (5%), Garlic bulb extract (5%), Bacillus thuringiensis (2 kg/ha), Castor oil (5%), Panchagavya (0.01%), Neem Seed Kernel Extract (NSKE 5%), Karanj oil (2%), and Beauveria bassiana (2 kg/ha), while the control received only water spray. Observations were recorded on the incidence and population buildup of major pests such as Maruca vitrata, Helicoverpa armigera, and Bemisia tabaci in relation to meteorological factors like temperature, rainfall, and relative humidity. The results revealed that the population of major insect pests varied significantly with climatic conditions, showing peak infestation during periods of high humidity (70-90%) and moderate temperatures (30-34 °C). Among all treatments, Neem oil (5%) and Bacillus thuringiensis (2 kg/ha) were found most effective in minimizing larval population and pod damage of Maruca vitrata, followed by NSKE (5%) and Beauveria bassiana (2 kg/ha). These treatments also resulted in higher grain yield and better seed quality compared to the control. The untreated plots recorded the maximum pest infestation and lowest yield. Economic analysis indicated that neem-based bio-pesticides and microbial formulations were not only effective but also profitable, with the highest benefit-cost ratio (B:C) ranging from 2.6 to 2.8, demonstrating their economic viability and suitability for eco-friendly pest management. The correlation studies between pest population and weather parameters revealed that M. vitrata showed a positive relationship with relative humidity and moderate temperatures, while heavy rainfall had a suppressive effect on pest activity. The study concluded that integrating bio-pesticides such as neem oil, Bacillus thuringiensis, and Beauveria bassiana provides a sustainable, eco-safe, and residue-free alternative to synthetic insecticides for the effective management of spotted pod borer and other major pests of green gram. The adoption of these bio-rational practices within Integrated Pest Management (IPM) frameworks can significantly reduce chemical pesticide dependence, improve environmental safety, and enhance the economic returns of pulse growers, particularly under the dry sub-humid agro-climatic conditions of Bundelkhand region.