In contrast to targeted spray applications, where bees are exposed in the treated crop, exposure of bees to dusts is caused by dusts in the seed bag and dusts abraded from the seeds which are emitted into the environment during loading of sowers and during sowing and drift into neighbouring flowering crops. The contamination of nectar and pollen in adjacent field crops and contact exposure to dusts on the treated plants are the most important routes of exposure of bees to dusts. To achieve a realistic pesticide exposure to bees foraging on flowers from bee attractive plants located next to fields sown with pesticide-treated seeds, specific requirements in terms of study design, test item application, and field experiment establishment need to be met.
As no commercial machinery for a targeted dust application on flowering crops is available, it is not possible to administer precisely target doses of AI/ha on flowering crops. Most field trials are conducted by sowing treated seeds and measuring drift into neighbouring areas. To achieve meaningful results, appropriate establishment of trials with sowing and drift of dusts into adjacent crops must be accomplished and one must generate proof of achieving the targeted exposure to bees. While the development of appropriate methods for dust trials continues, experimental designs that allow assessing pesticide effects on bee colonies have been effective and are described in this section.