NAAA Battles for Aerial Applications of New Insecticide—Isocycloseram—on All Crops and in All States

NAAA submitted comments this week on a proposal to register isocycloseram, a new insecticide with a novel mode of action. NAAA first became involved with the registration of isocycloseram late in 2024, when the registrant, Syngenta, reached out for NAAA’s assistance. During the registration process between Syngenta and EPA, EPA had indicated they intended to ban aerial application of isocycloseram for all crops except for cotton, and even then, only in specific locations. NAAA submitted a letter to EPA on behalf of Syngenta to support their efforts to get aerial application on the label for all crops.

The proposed registration approval for isocycloseram, released in May, was an improvement over the initial ban proposed by EPA, but still severely and unfairly restricts aerial applications. EPA proposed to approve aerial applications of isocycloseram for only corn, soybean, potatoes, and cotton. However, for corn and soybean, aerial applications would only be allowed in a limited number of states. To make matters worse, the top producing corn and soybean states were not on the list, meaning aerial applications of isocycloseram would not be allowed on corn and soybean in the states where they would likely be needed the most. For corn, aerial application of isocycloseram would only be allowed in CO, KS, NE, OK, and TX; for soybean, aerial applications would only be allowed in AL, AR, GA, LA, MS, MO, NC, OK, SC, TN, and TX.

As an additional setback, EPA proposed buffer zones for aerial applications next to aquatic areas that were not wind-directional. This would result in the areas being completely off limits for aerial applications of isocycloseram. This goes against numerous registration review decisions and EPA’s endangered species strategies, which all recognize drift only moves downwind and buffer zones are only needed when the wind is blowing towards the sensitive area. Furthermore, because the registration for isocycloseram began before EPA changed its policy to use the Tier 3 AgDRIFT model, the risk assessments for isocycloseram were conducted using the inaccurate Tier 1 AgDRIFT model.

NAAA comments on isocycloseram focused on pointing out how important aerial application is for corn and soybean production in many states beyond the limited list from EPA. NAAA also questioned why drift mitigations from the recently released insecticide strategy, and used for the proposed registration of isocycloseram, would be sufficient for protecting endangered species in some states but not in others. And NAAA once again pointed out that drift cannot move upwind, so using a permanent buffer zone to protect aquatic areas offers no additional protection than a wind directional buffer zone. NAAA also pointed out that EPA should re-conduct their ecological risk assessments using the Tier 3 AgDRIFT model.

NAAA will continue to follow the registration process for isocycloseram and fight for aerial application to be allowed on all crops and in all states.