Optimising Semi-Synthetic Diet for Sustained Laboratory Rearing of Maruca Vitrata and Studying Biological Performance Using Age-Stage, Two-Sex Life Table Analysis

Abstract

The legume spotted pod borer (Maruca vitrata) is a major pest of leguminous crops worldwide. A reliable, cost-effective semi-synthetic diet is essential for mass rearing under controlled conditions to support laboratory bioassays, plant resistance screening, biocontrol and toxicological studies. In this study, the biological performance of M. vitrata was evaluated on four semi-synthetic diets using the age-stage, two-sex life table approach. Key life table parameters such as survival rate (l_x), fecundity (m_x), reproductive value (V_xj) and life expectancy (e_xj) were recorded. Among the diets tested, diet-I significantly outperformed the other compositions, supporting higher fecundity (201.20 ± 20.46), a net reproductive rate (R₀ = 110.00) and an intrinsic rate of increase (r), indicating an enhanced population growth potential. Females reared on diet-I exhibited an earlier peak in reproduction and a higher cumulative output. Additionally, the effect of larval rearing density on development was assessed to optimise large-scale rearing. While increased densities resulted in marginally longer larval durations and reduced percentage survival, optimal outcomes were maintained at densities of up to 100 larvae/container. The cost of producing 1000 mL of diet-I was estimated at US Dollars ($) 5.46. Further, the diet-I supported long-term viability and continuous rearing over 10generations, with life history parameters showing minimal decline. Egg production/female ranged from 145.92 to 164.58, larval percentage survival remained above 78% and the average number of females/cohorts was stable (25.75 ± 1.97). The development analysis and validation demonstrated diet-I as the most effective and economically viable formulation for mass rearing of M. vitrata, offering a standardised protocol for future research and pest management studies.