Annual Bluegrass Weevil

Annual bluegrass weevil (ABW) is a serious pest of short-cut, coolseason turfgrasses, particularly annual bluegrass and creeping bentgrass, in the Mid-Atlantic and northeastern U.S. Because adult and larval populations vary throughout the season within a location, scouting is essential for selecting the proper insecticide and timing. Current recommendations for sampling ABW larvae involve breaking apart soil/turf plugs in a saltwater solution and counting the number of larvae that float to the surface (salt float). Noticing small larvae and sifting through the plant and soil debris pose challenges to this method. Use of heat extraction has been explored recently as an alternative to the salt float method.

Our research objective was to compare these two methods using soil plugs collected from two different golf courses in Virginia with an established ABW population. The heat extraction technique utilizes a heat lamp to dry the soil plug in a Berlese- Tullgren funnel and forces the larvae downward through the soil and into a catch jar in order to escape the heat. In 2020, larvae from matched pair plant canopy cores were extracted using either the salt float method or the Berlese-Tullgren funnel method. Results showed that the two extraction methods were 80% correlated with regards to the number of ABW larvae recorded, and there was no significant difference between the methods in extracted larvae. Our research demonstrates that both methods are comparable for extracting ABW larvae. The method used for ABW larvae scouting and sampling can be determined by the turfgrass manager’s time, experience, and their personal preference.