Annual Bluegrass Weevil

NEW PEST ALERT: Annual bluegrass weevil has been found in Wisconsin

In late June we were contacted about a potential annual bluegrass weevil (ABW) infestation at a golf course in central Wisconsin. The insects were confirmed as annual bluegrass weevil on July 1st after specimens were sent to both PJ Liesch at the University of Wisconsin Insect Diagnostic Lab and Dr. Ben McGraw at Penn State University. We believe the annual bluegrass weevil was transported to central Wisconsin on bentgrass sod purchased from the eastern part of the country and installed 7 years ago.

What is annual bluegrass weevil?

Annual bluegrass weevils are small, black beetles that can cause significant damage to annual bluegrass in the eastern part of the country. The damage to turf is caused by larvae that hatch from eggs in the spring. Initially, larvae feed from within the turfgrass stem. Older larvae become too large to fit within the stem of the plant and exit the plant to feed on the crown, causing severe damage.

What does damage from annual bluegrass weevil look like?

ABW larvae cause annual bluegrass to die in small, yellow or brown spots (Figure 1). Since the damage is to the crown, stand recovery is often very slow. As the infestation spreads and becomes more severe, the small spots can enlarge and affect large stands of annual bluegrass. There are reports of ABW damage on other golf course turfgrass species (e.g. creeping bentgrass), but the primary concern is on annual bluegrass.

Figure 1. Annual bluegrass weevil damage at a course in Wisconsin.

Should I be concerned at my course?

Not immediately. To date ABW has only been detected at one course in central Wisconsin, and ABW adults do not spread rapidly to surrounding areas. Prior to this case, the furthest west case of ABW in the Midwest was in Louisville, KY. However, ABW spread is difficult to stop entirely, and it’s likely that ABW infestations will slowly spread to surrounding areas.

How do I know if I have ABW?

Preventative control measures should not be implemented until ABW has been confirmed at your course. Scout for the adults in annual bluegrass stands beginning in mid-April to early May when GDD reaches 25 to 50 (base 50F, March 1st start) or when Forsythia is in full bloom. ABW adults are small (approximately 1/8” long), black, and have a curved snout (Figure 2). They resemble billbugs but are considerably smaller. ABW larvae are white with a red head and don’t have any legs (Figure 3). Wisconsin residents may submit physical specimens or email pictures to PJ Liesch at the University of Wisconsin Insect Diagnostic Lab ( Residents from outside Wisconsin can contact Dr. Ben McGraw ( at Penn State for more information about submitting adult specimens for identification.

Figure 2. Adult annual bluegrass weevil collected from a golf course in Wisconsin. Photo credit to PJ Liesch.

Figure 3. Annual bluegrass weevil larvae from a golf course in Wisconsin.

Additional Resources:

For questions about ABW ID in Wisconsin please contact PJ. Liesch at the UW Insect Diagnostic Lab. For questions about ABW management or ID outside of Wisconsin please contact Dr. Ben McGraw at Penn State University.


Thank you.

Paul Koch, PhD                                                                                                   Associate Professor                                                                                  Department of Plant Pathology                                                            University of Wisconsin – Madison

Ben McGraw, PhD                                                                                            Associate Professor                                                                                   Department of Plant Science                                                                               Penn State University

P.J. Liesch                                                                                                                      Insect Diagnostic Lab Manager                                                            Department of Entomology                                                                     University of Wisconsin – Madison