Annual Bluegrass Weevils

Diagnosis and Decision Making for Sustainable Annual Bluegrass Weevil Management 6 Decision Making and Management– Adults When deciding whether to treat adult ABW with pesticides, use scouting data to try to limit applications to only those areas where ABW are detected. Also keep in mind that poor timing and overuse of pyrethroids can result in insecticide resistance in ABW. If the decision is made to use a pesticide, be sure to time it carefully with peak adult activity at the playing surface. One week following pesticide applications, conduct follow-up vacuum sampling to gauge the effectiveness of the treatment and to make informed decisions about the need for later larval scouting. 1st Generation Larvae Shortly after adults reach peak activity at the playing surface edge, they begin laying eggs within the turfgrass stem. This occurs ~175 GDD (base 50) , generally corresponds with the full bloom stage of flowering dogwood and is an important timeframe for the monitoring and/or management of ABW larvae. Preventive management of larvae. In many cases where ABW has proven problematic in previous seasons, it is wise to follow an adulticide application with a preventive application of a systemic pesticide such as products containing the active ingredient chlorantraniliprole, or imidacloprid in locations such as Long Island, NY, where chlorantraniliprole and other anthranilic diamides are prohibited. This application should correspond with peak ABW egg laying to allow time for the systemic products to be taken up by the plant so they are active upon egg hatch. Unfortunately, there are no easy scouting indicators for monitoring eggs, but managers can rely on their records of areas where ABW adults were detected along with both degree day and phenological indicators as noted above. Curative management of larvae. Shortly after egg laying is also when larval monitoring begins, and in most Northeastern states, this typically occurs in May. The goal of larval monitoring is to identify the time frame when most larvae transition from third to fourth instar and exit the crown of the plant, entering the surrounding soil and becoming vulnerable to many insecticides. This generally coincides with peak bloom for Catawba rhododendron (Rhododendron catawbiense) and ~350 GDD (base 50) . Larval sampling to monitor for this stage should occur weekly in areas where high adult activity was previously detected. Scouting Procedures– Larvae Soil Collection. Using a turf plugger, collect soil cores just inside the fairway edge in areas where high adult activity was detected. Collect one soil core every 2-3 feet across the area under investigation (Figure 8A). Backfill soil plug holes, remove cores from plugger (Figure 8B), bag and label. Cores should be processed as soon as possible and not be allowed to dry out. Hand Sorting ABW larvae can be detected by hand sorting turf plants and soil plugs in the field. This method can be very effective in identifying when larvae begin to emerge from the turfgrass crown and inhabit the surrounding soil. However, it can also be labor- and time-intensive. Salt flotation This method generates the same high-quality data as hand sorting but allows for sampling from a greater area. Additionally, much of the method happens passively, meaning that larvae can be extracted while working on other tasks. The method also permits extracting young larvae from inside the turf plant as well as mature larvae inhabiting soil. Materials • Table salt • Tap water (lukewarm) • 16 oz. deli cups or similar container • Turf plugger • Divot mix for filling plug holes Method • Make a salt solution using a ratio of 4 cups of table salt to 1 gallon of lukewarmwater. The solution can be made the day before to ensure that the salt dissolves completely. Figure 8. Turf plug collection for monitoring of ABW larvae. A – Pattern of plug collection along fairway edge. B – Removal of soil from turf plugger.