SUSCEPTIBILITY OF THE LESSER MEALWORM, ALPHITOBIUS DIAPERINUS (COLEOPTERA: TENEBRIONIDAE) TO THE ENTOMOGENOUS NEMATODES STEINERNEMA FELTIAE, S. GLASERI (STEINERNEMATIDAE) AND HETERORHABDITIS HELIOTHIDIS (HETERORHABDITIDAE)

Abstract

The infectivity of Steinernema feltiae, S. glaseri and Heterorhabditis heliothidis for early-stage larvae, late-stage larvae, pupae and adults of the lesser mealworm were evaluated under different habitat conditions. When confined in petri dishes with nematode-treated filter paper, all beetle stages were highly susceptible to parasitism by S. feltiae, with LD50 values ranging from 9 to 56 nematodes per host Early-stage larvae (LD50 = 26) and pupae (LD50 = 36) were more susceptible than late-stage larvae (LD50 = 1,791) and adults (LD50 = 724) to H. heliothidis. Only adult beetles (LD50 = 714) were susceptible to S. glaseri. Late-stage beetle larvae were more susceptible to S. feltiae in rearing medium (LD50 = 24), broiler litter (LD50 = 2 58) and poultry manure (LD50 = 212) than to H. heliothidis, which caused less than 50% mortality at all dose rates in these substrates. Adults were less susceptible than larvae in these substrates, and mortality only exceeded 50% in litter treated with S. feltiae (LD50 = 971). Late-stage larvae were highly susceptible to both S. feltiae and H. heliothidis in sandy loam and clay soils, with LD50's ranging from 1 to 14 nematodes per larva. Pupal mortality was higher in sandy loam (S. feltiae LD50 = 46, H. heliothidis LD50 = 444) than in clay soil (S. feltiae LD50 = 95, H. heliothidis LD50 = 5,796).