Annual Bluegrass Weevils

Diagnosis and Decision Making for Sustainable Annual Bluegrass Weevil Management 2 Overview The annual bluegrass weevil (ABW), Listronotus maculicollis , is native to the Northeastern United States. ABW can have two to three generations per year and causes significant damage to golf courses in Northeastern and some Southeastern states. ABW adults overwinter in leaf litter, tall grasses, and other areas with dense organic matter that provide a buffer from harsh winter conditions. On a typical golf course, overwintering habitats include roughs, grassy native areas, forest edges, and tree and shrub lines. In spring — as early as March in upstate New York —ABW adults emerge from their overwintering areas and move toward golf turf playing areas to begin reproduction. This is when the ABW management season begins. For many reasons, management of ABW presents incredible challenges. First, the small size (about 1/8 inch in length) and cryptic nature of ABW adults make monitoring difficult. Second, as the life stages progress and ABW transitions through the egg and larval stages, observing ABW becomes increasingly difficult because most stages occur within the turfgrass stem. Complicating things further, as larvae mature, they emerge from the turf crown into the surrounding soil and proceed to feed on the crown and roots of the plant. Following the last larval development stage, larvae pupate below ground and the next adult generation emerges. This generation of ABW is more widely distributed on the golf course, and thus more difficult to find and diagnose than the previous generation. Finally, ABW development is highly asynchronous, meaning that the life stages of different individuals overlap, resulting in the presence of more than one life stage at a single time. Collectively, these factors make ABW a difficult insect to monitor and manage in an economically and environmentally sustainable way. However, by using proper scouting methods along with a well-informed decision-making process, you can improve the effectiveness and efficiency of ABW management at your facility. Traditionally, ABW management has focused primarily on scouting for and treating adults. However, to enhance control and to manage insecticide resistance in ABW, managers are encouraged to broaden their monitoring and management efforts to include ABW larvae in addition to adults. This publication provides the information needed to establish a successful ABW monitoring and management program. Overwintering Adults Spring offers the best chance for controlling ABW adults before egg laying. The primary goals for adult scouting are to determine: • Timing and location of ABW emerging from overwintering sites —when and where on each course. Recording these location helps to narrow scouting efforts later in the season and future seasons. • Pattern of ABW adult movement following emergence toward short-mown turf. • Timing of peak activity of ABW adults, meaning the point at which the majority of ABW adults are found at or within the playing surface (fairway, tee, green) edge. In the Northeast, scouting for adults should begin as close to March 1 as feasible, though some colder areas may not have adult activity until late March or early April. It is also beneficial to install a degree day monitor on site where possible to help make your scouting efforts as efficient as possible.* In Northeastern states, ABW emergence should begin soon following snow melt or soil thaw and often corresponds with the full bloom stage of forsythia. The primary areas to scout for ABW include ones with historical ABW presence/ damage and their overwintering habitat of accumulated leaf litter and clippings such as turf adjacent to native areas/forest edges and shrub lines. Once begun, adult scouting should continue weekly until peak activity is observed at the nearest playing surface, noted, and these areas monitored later for larvae. This stage generally coincides with the phenological stage of half green/ half gold on forsythia and occurs at roughly 110 –120 growing degree days (GDD) – base 50 beginning March 1. Scouting Procedures– Adults General Practice Early in the season, sample in turf directly adjacent to known or likely overwintering sites to pick up on the emergence of overwintered adults. As spring progresses and once adults are found, begin sampling progressively away from overwintering sites, toward the closest short-mown playing surfaces (fairways, tees, greens) to track the movement of adults to these areas (Figure 1). *Where helpful, degree day indicators associated with distinct ABW development stages have been included in this document.