Impact of a Microbial Pest Control Product Containing Bacillus thuringiensis on Brood Development and Gut Microbiota of Apis mellifera Worker Honey Bees

Abstract

To avoid potential adverse side effects of chemical plant protection products, microbial pest control products (MPCP) are commonly applied as biological alternatives. This study aimed to evaluate the biosafety of a MPCP with the active organism Bacillus thuringiensis ssp. aizawai (strain: ABTS-1857). An in-hive feeding experiment was performed under field-realistic conditions to examine the effect of B. thuringiensis (B. t.) on brood development and the bacterial abundance of the core gut microbiome (Bifidobacterium asteroids, Gilliamella apicola, the group of Lactobacillus and Snodgrasella alvi) in Apis mellifera worker bees. We detected a higher brood termination rate and a non-successful development into worker bees of treated colonies compared to those of the controls. For the gut microbiome, all tested core members showed a significantly lower normalized abundance in bees of the treated colonies than in those of the controls; thus, a general response of the gut microbiome may be assumed. Consequently, colony exposure to B. t. strain ABTS-1857 had a negative effect on brood development under field-realistic conditions and caused dysbiosis of the gut microbiome. Further studies with B. t.–based products, after field-realistic application in bee attractive crops, are needed to evaluate the potential risk of these MPCPs on honey bees.

Exposure of honey bees to mixtures of microbial biopesticides and their effects on bee survival under laboratory conditions

“…Research investigating the effect of microbial biopesticides on honey bee health is still developing (Borges et al 2021 ; Erler et al 2022 ), particularly their interaction with the gut microbiome (Steinigeweg et al 2023 ). In the present study, we reported for the first time how microbial combinations can affect honey bee survival under laboratory conditions.…”

“…aizawai is an effective entomopathogen against lepidopteran larvae. However, its semi-specificity was indicated recently depending on the reported cross-effects across insect taxa and orders (e.g., Babin et al 2020 ; Nawrot-Esposito et al 2020 ; Steinigeweg et al 2021 , 2023 ; Tudoran et al 2020 ; van Frankenhuyzen 2017 ). This shows that target-specificity is not always as strong as expected.…”

Nutritive and immunological benefits derived from the honey bee gut microbiome are threatened by anthropogenic stressors

“…Recent evidence suggests that honey bees contaminated with typical agricultural pesticides are also at risk (Motta et al 2020;Steinigeweg et al 2023;Traynor et al 2016). A study investigating pesticide residues on migrated honey bee hives found 171 different pesticide residues present in the wax, bee bread and adult workers (Traynor et al 2016).…”

The microbial status of bee families Apis melifera during the winter period

“…These diseases are dangerous and affect both adult bees and their brood (Salmonellosis, Collibacilosis, Viral septicemia, American and European foulbrood, Aspergyllosis, etc.). For this reason, the health of the bee families and the efficiency of their activity depends on the veterinary sanitary measures undertaken by the beekeeper in close contact with veterinarians (3,4,5,6).…”