After the spring thaw, many turf managers in the mid-Atlantic and northeastern states must begin the watch for the return of annual bluegrass weevils (ABW). These insects overwinter as adults in wooded areas and begin migrating toward turf areas where their offspring will feed on Poa annua, their preferred food source.
Keeping tabs on the migration and subsequent life cycle benchmarks is essential to timing a control strategy, which typically consists of multiple insecticide applications. A 2014 survey found that affected courses made an average of 3.9 insecticide applications per year targeting this pest.
Adulticide applications are recommended as the peak of their migration to turf areas. State extension, consultants, and manufacturer online sources can provide some regional guidance on timing, based on various scouting methods, growing degree day (GDD) modeling, or indicator plant phenology. Adults are on a mission to mate and do not cause significant damage. Although small, they may be observed as they migrate across the turf canopy from roughs or wooded areas. Some that reach greens end up in mower catch baskets, and pitfall traps along likely migration routes as well as soap flushes can be useful to keep tabs on movement. A paint screen sock duct-taped loosely over the end of a leaf blower converted to vacuum mode can also give a quick assessment of adults present. Forsythia that are half gold/half green are often referred to as a common indicator of peak migration, which is when adulticides are typically applied. Current adulticides include pyrethroids such as Quali-Pro Bifenthrin Golf & Nursery 7.9F or Quali-Pro Chlorpyrifos 4E.
Larval ABW Stages
Treatments shift away from adulticides once egg laying begins, which often coincides with dogwood and Eastern redbud trees in full bloom. Once eggs that were laid in the grass sheaths hatch, the larvae burrow into the stems and begin feeding. From this point forward, scouting becomes a little more involved. Submerging plugs in salt-saturated water after breaking up will float all life stages to the surface. Targeting the early larval stages is typically done with systemic-type products since they are inside of the stems. For now, industry standards for this stage are typically anthranilic diamides. Once rhododendrons are in full bloom, late-stage ABW larvae leave stems and begin feeding on crowns, which usually results in the most noticeable damage to the turf shortly thereafter. Since they are outside of the plant again, a number of contact-type products are players for this timing. Surviving larvae pupate and emerging “teneral” adults are orange-brown and can result in another round of insects and damage into the summer months, often with overlapping growth stages making selection and timing of effective control products more difficult.
Resistance and More Choices
The survey noted above and continuing industry feedback and monitoring indicate that the range of ABW is expanding and resistance to control options, especially adulticides, is on the rise. Limited choices for adult and early larval stage timings and staggered summer “escape” populations have created the need for more control options to avoid further complications with this pest.
Wouldn’t a new class of effective chemistry sound like a good idea? What if it were effective on multiple growth stages and less timing-sensitive? Remember the name, “Suprado,” and stay tuned to Quali-Pro for news and updates about this exciting product, new to the turfgrass industry, coming soon!
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Ian Rodriguez Technical Service Manager Quali-Pro