The Three P's of ABW Control
By: Brad Shaver, Ph.D.
Over the past few years there have been an increasing number of reports about annual bluegrass weevil (Listronotus maculicollis) damage to turfgrass. Discovered in 1931, this native beetle was historically only a concern in the northeastern United States. However, severe infestations have now been reported as far north as Canada, as far west as Ohio and as far south as North Carolina. Annual bluegrass weevil (ABW) is primarily a pest to closely-mowed annual bluegrass but it has been found causing damage to creeping bentgrass and perennial ryegrass adjacent to infested annual bluegrass. ABW is an increasingly important turfgrass pest because of its ability to cause devastating injury, and difficulty in achieving satisfactory control.
ABW are active from spring through fall. The adults are the overwintering stage and usually hibernate in the periphery of a golf hole in the top 1-2” of the soil profile. The most common overwintering locations are native areas, rough areas, under tree litter, and around the base of trees. Adults emerge during the spring of the year and make their way towards more closely mowed turf areas. The first eggs are laid shortly after feeding begins in the spring. ABW females chew through the leaf sheath and deposit eggs between the sheath and stem. Egg hatch occurs 4-5 days after oviposition (egg laying). The larvae pass through five instar stages. Young ABW larvae remain within the stem of the turfgrass plant for larval stages 1-3, where they feed on the stem of the plant. This initial damage is often mistaken for disease, drought or traffic damage. As the larvae grow and develop, they become too big to live within the leave stems and move into the soil for larval stages 4-5. The fourth and fifth instar stages cause the most damage of all stages, feeding on the crowns and surface roots of the turfgrass plant. In these stages, a single individual can damage up to 20 stems. A mature fifth instar will eventually become a prepupa and pupa before reaching the adult stage. Young adults (callows) are brown and eventually turn dark gray or black.
ABW can have up to three generations per year meaning that damage can occur throughout the growing season. Visually, damage from ABW is similar to and often confused with anthracnose. ABW causes yellow and brown patches, initially appearing along the perimeters of close-cut turf. Affected stems are easily removed from the plant with a gentle pull. Close inspection of the stem may reveal excrement left behind from ABW larvae. To learn more about ABW biology click here and here.
“Scout, Scout, Scout!!” – Mike Rincon, Fredericksburg, VA.
Having multiple generations per year makes controlling ABW more difficult compared to other pests such as white grubs, which have only one generation per year. Effective management programs monitor for ABW throughout the season. “Scout, scout, scout!!” says Mike Rincon, a Helena sales representative and branch manager of the Fredericksburg, VA location. Mike tells his customers that scouting is critical for satisfactory results. Indeed, achieving ABW control comes down to three important factors: proper timing, proper product selection, and proper product placement.
Timing
Begin scouting for ABW adults in the spring of the year. ABW activity often occurs in areas where previous damage occurred. Begin monitoring in areas where overwintering sites are fairly close to low cut turf. Monitor along edges of these areas, the edges of close-mowed turf and everything in between. Document movement towards tees, fairways and collars where mating, and eventually egg-laying occur. In the spring, look for adults crawling on the surface and in clipping baskets. Check for adults and larvae as the season progresses. Monitoring techniques such as soap flushes, pitfall traps and submerging plugs in salt water are useful for detecting adults and larvae. More information on these techniques can be found here. ABW adults are very small (3-4 mm long) so look closely! Another scouting technique is to use a vacuum. Yes, you read that correctly. The vacuum has a filter inside that catches ABW adults and older larvae. Mike, along with the two other salesmen working out of the Fredericksburg, VA location, Jeff Snyder and Tommy Adams, use the vacuum technique regularly throughout the season to help customers monitor for ABW.
It is important to keep good records and monitor the movement of ABW throughout the season, and from one year to the next. One way to do this is with INSPEX™ management services from Helena Chemical. INSPEX™ services provide customized graphical reports that help you visualize your entire course and map areas of ABW outbreak and damage. Click here to find out more about INSPEX™ management services.
Another good source of information about ABW is WeevilTrak™ by Syngenta. This free service offers real time updates and growing degree day information from across the northeastern US and information from university researchers and golf course superintendents. Click here to find out more about WeevilTrak™.
Product and Placement
Deciding what product to use is the second critical step to achieving effective ABW control. Different products are available depending on what stage ABW you are targeting. Systemic larvacides target larval stages 1-3 while they are inside the plant. Contact larvacides target and control larval stages 4-5 which live outside of the plant and may provide some control of earlier stages. Several adulticides are also available. Remember to rotate modes of action as much as possible to delay or prevent resistance from developing.
Product placement is the third and final step for effective ABW control. Be sure to read the label and talk to your sales representative to find out if the product should be applied to the leaves, the crown, or watered into the soil. Spray adjuvants are designed to help you get the most out of every application, and can be important when the applicator is forced to use less than ideal water volumes. You can read more about Helena adjuvants here.
Managing ABW is difficult but effective control can be achieved if you remember these tips: “Scout, Scout, Scout!!”, proper timing, proper product, and proper placement.
References
Dosckocil, J. 2009. Annual bluegrass weevil. North Carolina State University Cooperative Extension Insect Note 146. http://www.ces.ncsu.edu/depts/ent/notes/O&T/lawn/note146/note146.html
Peck, D.C., Diaz, M.D., and Seto, M. 2007. Annual bluegrass weevil. Integrated Pest Management Fact Sheet, Cornell University. http://www.nysipm.cornell.edu/factsheets/turfgrass/abw.pdf
Vittum, P.J., Villani M. G., and Tashiro H., 1999. Turfgrass Insects of the United States and Canada, 2nd ed. Cornell University Press, NY. 422pp.