The role of field dust in pesticide drift when pesticide-treated maize seeds are planted with vacuum-type planters.

BACKGROUND: Neonicotinoid-contaminated dust escaping pneumatic seeders causes exposure to non-target organisms such as pollinators. Two sources of dust have been reported: abrasion by talc which is added as seed lubricant during planting, and seed-to-seed abrasion occurring during seed handling, distribution and planting. We report a third important source that warrants remediation. Here, soil dust stirred up by planters was found to enter the vacuum air intake near seed metering devices.

RESULTS: The mean quantity of dust collected from the exhaust of a commercial pneumatic planter over a number of field sites and situations was 46 g ha-1 , ranging from 5.8 to 184.2 g ha-1 . While the clothianidin concentration in exhaust dust declined with increasing quantity of dust, total clothianidin recovered increased linearly within the study parameters. Up to 2.4 g ha-1 of clothianidin was recovered from planter exhaust, representing approximately 12.6% of the active ingredient applied to seed. A similar pattern occurred in the laboratory on a single standing planter unit using diatomaceous earth as surrogate field dust.

CONCLUSION: Field dust in pneumatic metering systems contributes significantly to clothianidin contamination in planter exhaust by seed abrasion. Adding diatomaceous earth as surrogate field dust to the Heubach seed dust protocol accounted for field dust abrasion and distinguished anti-abrasive properties of seed treatments. © 2017 Society of Chemical Industry.