Insecticidal Cry, or Bt, proteins are produced by the soil-endemic bacterium, Bacillus thuringiensis and some genetically modified crops. Their environmental fate depends on interactions with soil. Little is known about the toxicity of adsorbed proteins and the change in toxicity over time. We incubated Cry1Ac and Cry2A in contrasting soils subjected to different treatments to inhibit microbial activity. The toxin was chemically extracted and immunoassayed. Manduca sexta was the target insect for biotests. Extractable toxin decreased during incubation for up to four weeks. Toxicity of Cry1Ac was maintained in the adsorbed state, but lost after 2 weeks incubation at 25 °C. The decline in extractable protein and toxicity were much slower at 4 °C with no significant effect of soil sterilization. The major driving force for decline may be time-dependent fixation of adsorbed protein, leading to a decrease in the extraction yield in vitro, paralleled by decreasing solubilisation in the larval gut. (Résumé d'auteur)

The intensification of agriculture has promoted the simplification and specialization of agroecosystems, resulting in negative impacts such as decreasing landscape heterogeneity and increasing use of plant protection products (PPP), with the acceleration of PPP transfers to environmental compartments and loss in biodiversity. In this context, the present work reviews the various levers for action promoting the prevention and management of these transfers in the environment and the available modelling tools. Two main categories of levers were identified: (1) better control of the application, including the reduction of doses and of PPP dispersion during application thanks to appropriate equipment and settings, PPP formulations and consideration of meteorological conditions; (2) reduction of post-application transfers at plot scales (soil cover, low tillage, organic matter management, remediation etc. and at landscape scales using either dry (grassed strips, forest, hedgerows and ditches) or wet (ponds, mangroves and stormwater basins) buffer zones. The management of PPP residues leftover in the spray tanks (biobeds) also represents a lever for limiting point-source PPP pollution. Numerous models have been developed to simulate the transfers of PPPs at plot scales. They are scarce for landscape scales. A few are used for regulatory risk assessment. These models could still be improved, for example, if current agricultural practices (e.g. agro-ecological practices and biopesticides), and their effect on PPP transfers were better described. If operated alone, none of the levers guarantee a zero risk of PPP transfer. However, if levers are applied in a combined manner, PPP transfers could be more easily limited (agricultural practices, landscape organization etc.).

The present study was undertaken to assess the impact of a candidate mosquito larvicide, spinosad (8, 17 and 33 μg L−1) on a field population of Daphnia magna under natural variations of water temperature and salinity, using Bti (0.16 and 0.50 μL L−1) as the reference larvicide. Microcosms (125 L) were placed in a shallow temporary marsh where D. magna was naturally present. The peak of salinity observed during the 21-day observation period may have been partly responsible for the decrease of daphnid population density in all the microcosms. It is also probably responsible for the absence of recovery in the microcosms treated with spinosad which caused a sharp decrease of D. magna abundance within the first two days following treatment whereas Bti had no effect. These results suggest that it may be difficult for a field population of daphnids to cope simultaneously with natural (water salinity and temperature) and anthropogenic (larvicides) stressors. Significant interaction between salinity and spinosad exposure impairs the recovery of a natural population of Daphnia magna

International audience | Biocontrol strategies are viewed as an environment friendly alternative to the use of conventional synthetic pesticides to control pests or weeds in agrosystems and are expected to supersede the use of pesticides. Nevertheless, biocontrol solutions are not devoid of drawbacks. As encountered with conventional pesticides, one can expect side-effects of biopesticides on non-targeted organisms and/or ecosystem processes. The "bio-" prefix in the word "biopesticides" does it necessarily guarantee their environment safe profile? In this context, we call to mind the researchers of the network ECOTOX (French network of ecotoxicology; https://www6.inra.fr/ecotox) in the framework of a roundtable entitled "Biocontrol & Ecotoxicology" on the following questions: who is experienced in ecotoxicology in relation with biocontrol in its own research? To what extend would it be useful to introduce ecotoxicology in biocontrol? What is the fate of biopesticides in the environment? What role could we cast to ecotoxicology in biocontrol regulations? We report here a synthesis of the discussions engaged during the roundtable.