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Management Updates: Jul 8, 2020

Annual Bluegrass Weevils, White Grubs, Billbugs
July 8, 2020

Time for the New Summer ABW Generations in Southern New England

The spring generation of ABW has completed its development and the adults of that generation are at the peak of their activity now. It is still possible to see some pupae and larvae in some locations, however the vast majority of ABW are adults now, mating and laying eggs. GDD accumulation is about 1000 for Southern New England.

Even though this spring was unusual and caused a prolonged adult activity period, overall larval development was relatively synchronous with clear peaks and relatively narrow distribution of different larval instars and pupae at any given sampling. This probably occurred as a result of the sudden and intense onset of hot temperatures after the extended cold spell. For the most part, if standard recommended management programs were followed, ABW larvae were reasonably manageable this spring. However, hot and dry conditions stressed Poa annua at the time when the most intense ABW feeding occurs, exacerbating damage.

It is usually harder to find a perfect timing for the application to manage summer activity. It is important to monitor larval development and density to prepare for a larvicide application, if needed. By the end of this week or early next week, small larvae will be predominant in many locations. However, first and second instars are hard to detect in samples using available methods. In approximately 1.5–2 weeks, larger larvae will most likely start feeding outside of the stem and will be easier to notice. Please be advised that these are general guidelines and predictions, based on trends observed in the region. To pinpoint exact timing it is recommended to look at the samples from your location or refer to the WeevilTrak sites relevant to your location.

White Grubs

Adults of oriental and Asiatic garden beetles are at the peak of their flight, and Japanese beetle adult activity is increasing. Adult oriental and Asiatic garden beetles are flying at night (~8:30-10:00 PM) and are attracted to light(oriental beetles also sometimes fly during the day)Japanese beetle adults are active during the day and can be observed on many ornamental plants. Adult flight is a good indication for scheduling neonicotinoid preventive applications, targeting young larvae that will be hatching from eggs. Ideally all applications should be completed by the end of July. It is too late to apply chlorantraniliprole (AceleprynTM) for grubs. The window of opportunity for chlorantraniliprole was earlier, until June 15. Another diamide, cyantraniliprole (FerenceTM) can be applied at the same time as neonicotinoids. Golf course superintendents can target both grubs and ABW larvae if a cyantraniliprole application is made a bit later (in about 1.5-2 weeks).

Please note: Neonicotinoids can be toxic to pollinators including honeybees and wild bees. Cyantraniliprole is highly toxic to bees, even though it belongs to the same chemical class (anthranilic diamides) as chlorantaniliprole, which has low bee toxicity. Several measures could be taken to reduce exposure of foraging bees to insecticides: (1) avoiding application on flowering plants, (2) mowing before the application to reduce flowers which attract pollinators, (2) watering in products after application, (3) using granular formulations, (4) avoiding spraying during high winds to minimize drift, (5) and considering spraying in the evening or early in the morning when bees are not foraging. For more information on this topic, see our Neonicotinoid Turf Insecticides and Pollinators fact sheet.

It is important to know which white grub species are present and active at your location. For most locations in southern New England, oriental beetle grubs are the most dominant. However, species composition varies and can be affected by the specific location and the surrounding landscapes. If you noticed many Asiatic garden beetle (AGB) adults flying in your area, neonicotinoid application will most likely not to be effective against this species. Fortunately, AGB is smaller than other grub species and turf can tolerate higher densities (up to 20 per sq. ft.). In addition, AGB frequently occurs in lower maintenance turf, so they rarely cause damage requiring curative application. Monitoring turf quality and grub abundance will determine the need for the curative applications.


It is time to watch for billbug damage. If you notice damage in an area with known or suspected billbug infestation, perform a “tug” test: pull the damaged grass, if it easily breaks off and you see uneven/chewed up ends with sawdust-like larval frass, billbugs are possible culprits. Ideally, soil samples should also be taken and examined for larval activity. Most of the larvae can be found in the thatch zone. Remember that billbug damage often resembles summer dormancy, so lawns that have been struggling in the recent high temperatures and dry conditions may appear to be dormant, but in fact there may be billbug larvae feeding in the area. If that is the case, the turf may not recover when cooler temperatures prevail in September.


Submitted by: Dr. Olga Kostromytska and Dr. Pat Vittum