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- Title
Bacillus thuringiensis ssp. aizawai – Observations on honey bees and distribution in colony matrices under field conditions.
- Authors
Erler, Silvio; Steinigeweg, Charlotte; Beims, Hannes; Eckert, Jakob H.; Janke, Martina; Wirtz, Ina P.; Richter, Dania; Pistorius, Jens; Alkassab, Abdulrahim T.
- Abstract
Microbial pest control products are commonly applied worldwide as alternatives to avoid potential adverse effects of chemical plant protection products. Here, we aimed to evaluate the biosafety of a commercial product containing Bacillus thuringiensis ssp. aizawai (strain ABTS-1857) using four different approaches: 1) laboratory chronic exposure to evaluate the survival of adult and larval bee, 2) in-hive feeding under field conditions to examine the effect of B. t. on brood development and the core gut microbiome of adult bees, 3) semi-field colony-feeding to determine contamination levels of B. t. spores in various matrices, and 4) a field trial with spray application in a bee-attractive crop to estimate potential environmental accumulation and exposure of honey bee colonies. Adult bee and larval survival were negatively affected after chronic exposure depending on the tested concentrations; however, pollen feeding to adults promote survival of treated bees and delay the effects. Under colony conditions, treated colonies showed a higher brood termination rate and a significantly lower normalized abundance of the core gut microbiome in worker bees. B. t. spores were detectable in all matrices at different concentrations, decreasing over time under semi-field conditions. High spore levels were present in honey sacs and pollen pellets immediately after application. No spore reduction was seen in stored matrices like nectar and bee bread. In conclusion, the pest control product containing B. t. strain ABTS-1857 showed a negative effect on exposed bees under laboratory as well as field conditions, for instance on colony development and caused dysbiosis of the gut microbiome. However, further field-realistic exposure studies in bee attractive crops are needed to evaluate the potential risk of such products on honey bees.
- Subjects
HONEYBEES; BACILLUS thuringiensis; BEE colonies; PROPOLIS; LABORATORY infections; GUT microbiome; BEEHIVES
- Publication
Julius-Kühn-Archiv, 2023, Issue 474, p134
- ISSN
1868-9892
- Publication type
Article