Last week NAAA submitted comments to the EPA on their proposed interim decision regarding the reregistration of Glyphosate to ensure its continued safe use via aerial application. The EPA is required by FIFRA to review the registrations for all crop protection products every 15 years. An Interim decision was used by the EPA instead of a full re-registration of Glyphosate because Endangered Species Act and pollinator protection assessments still need to be completed before full reregistration can occur.

NAAA agreed with some of the proposed requirements for aerial application in the interim decision. The drift mitigation language showed EPA has been listening to previous comments from NAAA. Prior proposed interim decisions for other products had capped wind speeds for aerial applications at 10 mph. The proposed drift mitigations strategies for Glyphosate increased the limit on wind speed to 15 mph. The only additional requirement for applying in wind speeds of 11 to 15 mph is that boom length be reduced to a maximum 65 percent of wingspan for fixed wing aircraft and a maximum of 75 percent of rotor diameter for helicopters. For applications at wind speeds at 10 mph or lower, maximum boom length would be 75 percent of wingspan for fixed wing aircraft or 90 percent of rotor diameter for helicopters.

Additional drift mitigation language included not making applications during an inversion and a half swath displacement would be required on the downwind edge of fields. NAAA suggested a medium droplet size, based on the American Society of Agricultural and Biological Engineers (ASABE) Standard S572.1 for droplet size classification, for aerial applications of Glyphosate. Maximum aircraft height would be limited to 10 feet unless safety required a greater height.

One item NAAA objected to in the proposed interim decision for glyphosate was the lower maximum single application rate for aerial applications compared to ground applications. This lower maximum single use rate would mean aerial applicators could not apply as much Glyphosate per acre as a ground applicator could in a single application. NAAA pointed out that this restriction was based on risk assessments completed using erroneous assumptions in the AgDRIFT Tier 1 model used to estimate drift from aerial applications. While the proposed maximum single use rate for aerial application was higher than commonly used single use rates, NAAA pointed out that higher use rates may be required for weed populations that begin developing resistance to Glyphosate. Restricting the maximum single use rate for aerial application compared to ground would eliminate the option to use aerial application to control resistant weeds, which could prove disastrous to growers if wet conditions prohibited the use of a ground sprayer.

NAAA recommended that aerial applications get the same maximum single use rate as ground applications. If additional drift mitigation strategies are needed in order to apply the higher single use rates using aerial application, NAAA suggested that boom length be reduced to a maximum 65 percent of wingspan for fixed wing aircraft and a maximum of 75 percent of rotor diameter for helicopters no matter what the wind speed. A coarse droplet size requirement for the higher single use rates of Glyphosate would also be acceptable.