Assessment of the impacts of microbial plant protection products containing Bacillus thuringiensis on the survival of adults and larvae of the honeybee (Apis mellifera)

Abstract

This study was aimed at evaluating the effect of a microbial pest-controlling product (MPCP) with the active substance Bacillus thuringiensis ssp. aizawai (strain: ABTS-1857) on adults and larvae of honeybees. To determine the contamination levels of Bt spores in different matrices, a colony-feeding study under semi-field conditions was performed. Furthermore, two chronic adult trials and a chronic larval study were conducted under laboratory conditions to test the effects of different concentrations of the plant protection product (PPP) on the development and mortality. Possible modifications of the chronic oral toxicity test were assessed by additional pollen feeding. Our results showed that Bt spores were detected in all matrices over the entire test duration in different concentrations, decreasing over time. The survival of adult bees and larvae was negatively affected in laboratory conditions after a chronic exposure to the MPCP depending on the tested concentrations. Moreover, the earliest sign of bee mortality, resulting from exposure to ABTS-1857, was recorded only after 96 h at the highest tested concentration. Pollen feeding to adults significantly increased the survival of the treated bees. In conclusion, the PPP with the Bt strain ABTS-1857 showed an effect on the mortality of adults and larvae under laboratory conditions. Further studies with Bt-based PPPs under realistic field conditions are necessary to evaluate the potential risk of those MPCPs on honeybees.

Drosophila suzukii Susceptibility to the Oral Administration of Bacillus thuringiensis, Xenorhabdus nematophila and Its Secondary Metabolites

“…Some reviews summarize the potential of isolated Xn or Bt in the biological control of vectors and insect species harmful to agriculture [ 18 , 44 , 45 , 46 , 47 ]. However, the efficacy of these pathogens, when used in single, does not always provide satisfactory results; in addition, their efficacy often requires high concentrations of the pathogen, which can interfere with the life cycle and affect other beneficial organisms present in the environment [ 48 , 49 ]. The reduction of the administered concentrations and the improvement of the rapidity of action, could be achieved by combining different bioinsecticides, thus by exploiting the possible synergistic or additive potential of the applied pathogens [ 9 , 50 , 51 , 52 ].…”

Determination, distribution, and environmental fate of Bacillus thuringiensis spores in various honeybee matrices after field application as plant protection product

“…Colonies were identified as Bt by qPCR, amplifying a partial sequence of the CryIAa gene (Ogunjimi et al 2000;Steinigeweg et al 2021). Accordingly, a random colony was resuspended in 50-µL ddH 2 O, followed by bacterial lysis at 95 °C for 15 min.…”

“…Several reports regarding direct and indirect cross-effects of Bt formulations and their toxins across insect taxa and orders recently indicated the semi-specificity of Bt (van Frankenhuyzen 2017; Redmond et al 2020;Coyle et al 2000;Babin et al 2020;Nawrot-Esposito et al 2020;Tudoran et al 2020). Lepidopterantargeted formulation, containing Bta ABTS 1857, has demonstrated increasing mortality of adult and larvae of honeybees after chronic exposure under laboratory conditions (Steinigeweg et al 2021).…”

“…With no information about the realistic exposure yet available, the viability and environmental fate of Bt spores in the collected matrices, i.e., nectar and pollen, after application in different bee-attractive crops have to be investigated. Recently, we considered the distribution of Bt spores within the colony in several matrices after an artificial in-hive feeding experiment, resulting in the presence of Bt in all matrices at different concentrations over 2-3 weeks (Steinigeweg et al, 2021).…”

Varroa destructor from the Laboratory to the Field: Control, Biocontrol and IPM Perspectives—A Review

“…They reported that, after being treated with Bt for 24 h, V. destructor trembled, regurgitated, with intestinal inflammation (dysentery) and eventually died [ 211 , 212 , 213 ]. Short-term experiment showed no lethal effects among A. mellifera adults or larvae and possibly reduced vertical displacement [ 213 , 214 ] whereas chronic exposure to Bt induced precocious mortality for adults and larvae bees [ 215 ]. A lack of field studies does not allow to consider Bt as a resolutive method against the mite.…”