Control of Plodia interpunctella (Lepidoptera: Pyralidae), a pest in Bombus terrestris (Hymenoptera: Apidae) colonies

The bumble bee Bombus terrestris L. is an important pollinator of commercial crops. Mass-rearing of bumble bees under controlled conditions is susceptible to pest outbreaks such as the Indian meal moth, Plodia interpunctella L. This study showed that pollen collected from pollen traps at honey bee colonies can be contaminated with eggs of the Indian meal moth and that the eggs can hatch under bumble bee rearing conditions. Storage of pollen at −60 °C for more than 3 weeks can prevent an infestation of P. interpunctella in bumble bee colonies via pollen. Storage at −20 °C is less effective. Although P. interpunctella larvae slightly prefer pollen as their food source, they also feed on bumble bee pupae, especially when little pollen is present in a bumble bee colony. Spraying with the microbial insect pathogen Bacillus thuringiensis Aizawai at a concentration of 1 g/L water can control P. interpunctella (99.8% mortality) without harm to the bumble bee colonies. Higher concentrations have a negative impact on bumble bee colonies. Other B. thuringiensis strains, Kurstaki and Kurstaki Plus, are less effective.