Golfdom, February 2019

Super Science THE ABCS OF ABW Mowing down weevils By Ben McGraw Ph D M any turfgrass managers in northeastern North America would rather forget the 2018 growing season Record breaking rainfall throughout the region affected most aspects of turfgrass management including insect pest control The annual bluegrass weevil ABW Listronotus maculicollis is one insect pest that flourished in the wet weather and was particularly difficult to control with our standard arsenal of insecticides The weevil is challenging to manage even in a normal year given that early larval instars are hidden within the plant These cryptic stages are difficult to detect and nearly impossible to control with most if not all insecticides This creates a need to manage the pest either preventively targeting Research provided and funded by USGA adults prior to egg laying or curatively as larvae emerge from the plant to feed externally on the crown Both chemical management strategies have their advantages and disadvantages with each requiring precision timing Though many superintendents find it desirable to reduce populations preventively only two chemical classes provide even moderate control of adults The fear of creating a pyrethroid resistant or possibly a multipleinsecticide resistant population one that is less sensitive to nonpyrethroid compounds as well has many choosing to solely target larvae Curative controls are more selective than broadspectrum adulticides yet are relatively more expensive and require a detailed monitoring program to determine population structure Even with this information spring 2018 curative applications required dodging heavy rainfall and saturated soils We observed numerous product failures including time tested standards in this years field trials where applications were made in advance of heavy greater than 1 inch or prolonged rainfall Clearly relying solely on chemical insecticides to reduce ABW populations is a weak strategy and a more integrated control approach is needed to manage the ABW in the future MECHANICAL REMOVAL OF ADULTS Over the last four years members of the Turfgrass Entomology Laboratory at The Pennsylvania State University have been investigating the impact that cultural controls specifically mowing nitrogen fertilization and irrigation have on reducing ABW populations or damage severity The project was initiated after reviewing superintendent responses to a 2016 ABW management survey It is uncommon to observe damage to putting surfaces maintained at or below 0125 inch though adjacent collars 025 inch and higher may be severely affected Superintendents reported much greater ABW incidence in collars than greens Additionally the percentage of greens experiencing turf loss increased linearly with increases in height of cut suggesting that mowing 34 Golfdom February 2019 Golfdom com PHOTO BY BEN MCGRAW FIGURE 1 Time lapse photography was used to capture annual bluegrass weevil ABW surface movement in growth chamber studies Weevils were marked with a UV pen and placed in groups of five on a Poa annua plug The black light illuminated the mark during dark periods