Any time a turfgrass pest has the ability to evolve, there is always a chance it will develop resistance to control products and create problems. One example is the annual bluegrass weevil (ABW), which has been a problem throughout the Northeast for decades and continues to expand its range into more states. As we know, controlling this pest is challenging because there are different life stages with multiple generations each year and control products need to be timed appropriately, which is not easy when scouting for a 1/8-inch adult or tiny larva. For many years, control products were limited and we know insecticide resistance is a real concern, which makes the release of any new control product a very good thing.
Recently, the novel active ingredient isocycloseram (Atexzo) was released by Syngenta and is the first ABW insecticide in a new class of chemistry (Insecticide Resistance Action Committee (IRAC) Group 30). With the threat of potential resistance, having a novel active ingredient for turf in a new IRAC group makes isocycloseram an important new tool in ABW control programs. Having a product with a new mode of action is greatly helpful in not only delaying resistance, but it is also labeled for use on adults as well as all larval stages and field trials have demonstrated its effectiveness on both life stages, which allows for longer windows of application. Research conducted in Pennsylvania demonstrated that isocycloseram effectively controlled early larval stages (first through third instars) of ABW when applied at the rate of 0.089 to 0.134 pounds of active ingredient per acre (De Luca & Dant, 2025).
As with managing all turfgrass pests, a good program for controlling ABW includes scouting, monitoring population levels and applying any control products according to manufacturers’ labeled recommendations. Rotating modes of action should be a priority when feasible and keeping tried-and-true curative products on the shelf is always good practice. With all chemical control programs, effectiveness is directly related to growing the strongest turf you can. If the turf is weak, then you often can’t spray your way out of problems.
Reference
De Luca, M., & Dant, L. (2025). Control of early larval instars of annual bluegrass weevil in turfgrass with isocycloseram, a new isoxazoline insecticide. International Turfgrass Society Research Journal, 15, 1071–1074. https://doi.org/10.1002/its2.70064
Northeast Region Agronomists:
Darin Bevard, senior director, Championship Agronomy – dbevard@usga.org
Elliott L. Dowling, regional director, East Region – edowling@usga.org
Brian Gietka, agronomist – bgietka@usga.org