A device for pneumatic precision drills reducing the drift of the abrasion dust from dressed seed

The effect of drift of dust containing insecticide active ingredients (a.i.) derived from dressed seed and observed mortality or sub-lethal effects on honey bees (. Apis mellifera L.) has been recently investigated. Pneumatic precision drills used in maize sowing were considered among the main causes of the phenomenon. To reduce dust spread, the drills have subsequently been equipped with air deflectors that redirect the vacuum fan air outlet towards the ground, resulting in an unsatisfactory 50% reduction of a.i. concentration, with continuing sub-lethal effects on honey bees. We developed an effective prototype device for pneumatic drills, which uses partial recirculation and filtration of the air. Static tests (simulating sowing of maize seed treated with imidacloprid) were carried out to evaluate the prototype's efficiency and to provide information on the main characteristics of dust particles. Gravimetric and chemical analyses of samples showed, respectively, reductions of 98% of the total dust and of 97%. of the a.i which resulted from the application of the prototype. Particles with diameter >5?m were nearly completely eliminated. For particles with diameters <4?m, a lower reduction was observed, the effect of which, anyway, was counterbalanced by the lower overall mass of fine particles.