Strain-dependent resistance of yellow mealworm (Coleoptera: Tenebrionidae) to bacterial infection with and without probiotic supplementation

Tenebrio molitor L. (Coleoptera: Tenebrionidae) larvae are increasingly farmed worldwide as a sustainable source of edible animal protein, but pathogen outbreaks can severely reduce productivity and revenue. As with other forms of agriculture, identifying and rearing naturally disease-resistant strains could reduce such losses. Here, we compared the resistance of 10 mealworm strains to infection with the entomopathogenic bacterium Serratia marcescens Bizio and further assessed the effects of 2 commercial probiotics on the resistance and performance of 3 strains previously known to have wet food differential responses. Our results revealed clear strain-dependent differences in yellow mealworm growth, survival, and biomass in response to bacterial infection. While probiotic supplementation did not reduce mortality, it had variable and strain-specific effects on larval growth and yield, both when infected and under healthy conditions. These findings demonstrate that bacterial resistance in T. molitor is influenced by genetic background and highlight the need for strain selection in commercial farming. Probiotic use may provide benefits in certain strains, but outcomes are inconsistent, underscoring the importance of tailoring rearing practices to strain-specific responses.