Optimizing temperature and humidity dynamics in laboratory mass rearing of Trichogramma egg parasitoids on the host Galleria mellonella

Considering the global challenge of artificial multiplication of biocontrol agents in managing agricultural pests, our study attempted to develop an amenable, cost-effective multiplication technique for two indigenously identified parasitoids, Trichogramma chilonis and Trichogramma evanescens, on locally available host wax moth (Galleria mellonella) eggs in varied temperatures (15, 20, 25, 30, and 35°C) and humidity regimes (55, 65, and 75%), following a completely randomised design with three repetitions. According to the three-way ANOVA, the individual and combined effects of two factors, temperature and humidity, differed significantly for most of the studied variables, except for the factor of parasitoids. Maximum adult emergence was achieved at 25°C with 65% relative humidity for both species, T. chilonis and T. evanescens. A combination of 25°C with 65% RH turned out to be the optimal abiotic conditions for most of the variables, such as parasitoid longevity, fecundity, egg mortality, and male–female ratio. Notably, no statistical variation was recorded between 25°C and 30°C alongside 65% and 75% RH. Correlation analysis demonstrated that temperature had a significant positive relation with all variables, while cubic regression indicated that increased temperature up to a certain point accelerated the adult emergence rate and egg parasitising rate, explaining 76.3% and 71.6% variability, respectively. Principal component analysis identified fecundity and oviposition period as key variables accounting for the maximum variance. Additionally, a three-variable contour depicted a significant positive relation between egg emergence rate and egg parasitising rate (0.84**). Thus, the research findings paved the way for parasitoid mass rearing at low investment, facilitating sustainable, eco-efficient management of lepidopteran agricultural pests.