Rearing protocol of Euschistus heros (F.)(Heteroptera: Pentatomidae) using soybean grains with different crude protein contents

The neotropical brown stink bug, Euschistus heros (F.) (Hemiptera: Pentatomidae), is one of the main soybean pests in South America, causing significant yield and quality losses. Current management relies heavily on synthetic insecticides, which pose environmental and health risks, while sustainable alternatives such as biological control are limited by the availability of parasitoids. The large-scale production of egg parasitoids requires continuous stink bug colonies, which are traditionally maintained on fresh green bean pods—an approach hindered by seasonality, perishability, and high labor costs. This study aimed to evaluate the feasibility of rearing E. heros exclusively on dry soybean grains, with emphasis on the effects of different crude protein contents on insect development and reproduction. Two experiments were conducted: the first compared nymphal performance on soybean, peanut, and common bean seeds; the second assessed biological parameters of insects fed on eight soybean lines differing in protein content (29.6–41.3%). Results demonstrated that dry soybean and peanut seeds supported nymphal survival and development, while all nymphs fed on common bean died within three days. Across soybean lines, protein content did not significantly influence developmental time (~ 22 days), survival (46.4–78.6%), adult mass, longevity, fecundity, or sex ratio. Females developed slightly faster and were heavier than males, consistent with sexual dimorphism in stink bugs. The findings confirm that dry soybean grains, regardless of protein levels, are a viable year-round diet for E. heros , offering a practical, low-maintenance, and cost-effective alternative to fresh diets. This protocol enhances the scalability of parasitoid production programs, supporting integrated pest management strategies in soybean systems.