Rethinking Lesser Mealworm Management: New Evidence from Two Entomopathogenic Nematodes

Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) is a common pest in poultry farms, causing significant economic damage, spreading easily and quickly. The species is resilient, adaptable, and capable of thriving in a variety of environments, and both larvae and adults can hide in hard-to-reach places; thus, control becomes highly challenging. Moreover, the species has developed resistance to commonly used insecticides, increasing the need to adopt integrated pest management strategies. Hence, this study examined the mortality dynamics of A. diaperinus larvae exposed to the entomopathogenic nematodes (EPNs) Heterorhabditis downesi Stock, Griffin & Burnell 2002 (Rhabditida: Heterorhabditidae) and Steinernema kraussei (Steiner, 1923) (Rhabditida: Steinernematidae) across a range of temperatures, dose rates, and exposure intervals. The patterns of larval mortality closely followed the classical EPN infection timeline: limited mortality during the first hours, a pronounced increase between day 2 and 4, and high cumulative mortality after day 8. Steinernema kraussei produced moderate early mortality, increasing by day 8, across all tested temperatures, reflecting its relatively slower but effective infection progression. In contrast, H. downesi induced higher early mortality at moderate temperatures and stronger dose-dependent responses. Temperature significantly modulated infection in both species, with reduced performance at 35 °C, particularly for H. downesi, although high-dose treatments achieved substantial mortality. The significant temperature × dose × time interactions align with established EPN biology and previous research on both species and, overall, the results confirm that they both possess strong pathogenic potential against A. diaperinus, while their performance characteristics support their suitability as biological control agents for poultry facilities.