Annual Bluegrass Weevil, Listronotus maculicollis (formerly Hyperodes)
IPM Steps to Reduce Annual Bluegrass Weevils
1. Sample for Pest
Confirm the presence of annual bluegrass weevils before you treat.
Where to find it while inspecting: Look for this tiny black weevil in bluegrass or bluegrass mixed turf. Damage will show up as thinning spots. Listronotus aka ABW (annual bluegrass weevil) walks from leaf litter in fields in the spring to turfgrass. The best scouting method is soapy flush, which will produce different insects including the ABW. FLOTATION METHOD OF SCOUTING. Soften the soil a little by pouring some water out of a watering can. Insert one end of the can into the ground at least two or three inches, leaving at least four inches above the ground. Fill the can with water from a garden hose (with moderate pressure) and wait about five minutes. Insects will float to the surface of the water, where you can count them.
2. Proper ID
Are they annual bluegrass weevils?
Size and Appearance: ABW adults are ~1/8" long (half the size of billbugs and about the same size as another small black turf pest, Black Turfgrass Ataenius). Larvae are legless with an obvious brown head capsule and develop from 1/25" to 1/6" just before pupation.
3. Learn the Pest Biology
What is the life cycle of annual bluegrass weevils?
Life Cycle: Adults overwinter in longer grass close to mowed turf. In spring they walk back into shorter turf and females lay eggs; throughout the season 2–3 generations may occur, meaning multiple stages are found at any given time. Last season adults go to overwintering sites.
Preferred Food Sources: Turfgrass stems, primarily.
Preferred Habitat: Close-mown turf, primarily annual bluegrass, is first choice. Adults overwinter nearby in longer, unmown grasses. Larvae stay in thatch or enter into grass stem.
4. Determine Threshold
How many annual bluegrass weevils are too many?
Threshold: 20–80 depending on condition of grass and temperatures. Stressed summer grasses will fail much faster than spring grasses. In high priority sites such as golf courses, 10 may be the threshold number. It can be difficult to scout for ABW. In areas of turfgrass damage, you may want to use a soapy water flush to determine populations.
5. Choose Tactics
Creating a healthy soil condition and understanding turfgrass’s needs is the first step in reducing turf pests. What can I do to treat, reduce, or prevent annual bluegrass weevils?
Best Management Practices: Reduce the amount of bluegrass in turf where ABW has traditionally been a problem by overseeding year after year with non-bluegrass seed. Entomopathogenic nematodes (Steinernema carpocapsae) have been known to cut back ABW infestations when applied early in the season.
Treatment Methods: In extreme cases where it has been determined ABW is the culprit, insecticide treatments may be necessary. Contact a certified pest applicator and follow all regulations in your district and state.
Was the tactic successful? Record the date pests were first noted, and the tactic you used, and its success. Use one of our RECORD KEEPING tools.
For More Information:
When a pesticide application is necessary, all necessary and required precautions are taken to minimize risk to people and the environment and to minimize risk of pesticide resistance or pest resurgence. Pesticide use in your school may be prohibited or regulated by local policies or state and federal regulations. Risk reduction methods can include, but are not limited to, spot-treatment, the use of gel or paste bait formulations placed in inaccessible locations, injection into a crack or crevice, and other methods that reduce potential exposure.