Golf Course Management

JUL 2016

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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07.16 GOLF COURSE MANAGEMENT 85 CUTTING EDGE Teresa Carson Improving a predictive model for billbug management Billbugs (S eno orus species) have been identifed as the most problematic insect pest of turf in the Intermountain West. Most infor - mation about billbug phenology comes from a degree-day model developed in the eastern U.S. and based on bluegrass billbug popula - tions. We conducted a feld study to examine seasonal activity of billbugs in turfgrass to im - prove our understanding of billbug biology and management in the Intermountain West. We found a complex of three billbug species: bluegrass billbug (S. parvulus), hunting bill - bug (S. venatus vestitus) and Rocky Mountain billbug (S. cicatristriatus). Species composition and density of adult populations varied among sites, and differences in elevation, annual pre - cipitation, management, and average annual high and low temperatures could be contrib - uting factors. The frst occurrence of adult billbugs in Utah was calculated to be several weeks earlier (0 to 15 DD 10 ) than predicted by the current model (155 to 195 DD 10 ). Popula- tions of the damaging larval stages were high- est two weeks after adult peaks. Adjusting the current model to have an early biofx (Jan. 13 vs. March 1) and lower temperature threshold (3 C vs. 10 C) appears to improve the model ft for our region. Our proposed model pre - dicts frst occurrence of billbugs at 38 DD 3 ; 30% adult emergence at 548 DD 3 ; and peak adult activity at 754 DD 3 . Data from multiple seasons is being assessed to further develop the proposed degree-day model and optimize timing of management for billbugs in our re - gion. We are using this information to test the effcacy of biological and chemical control tac - tics on billbug suppression. — Ricardo Ramirez, Ph.D. (ricardo.ramirez@usu.edu), and Madeleine Dupuy, Utah State University, Logan, Utah ABW invades North Carolina The annual bluegrass weevil (ABW) has, in recent years, become a challenging cool- season turfgrass pest in western North Caro - lina. All previous research on developing an effective management approach to ABW had been conducted in the northeastern U.S., but in 2015, sites on golf courses in the North Carolina mountains were sampled each week from March until September. When com - pared with data previously collected from the northeastern U.S., degree-day accumulation milestones were not consistent with the emer - gence of different life stages of ABW in North Carolina. The frst overwintering adults were recovered from soapy water fushes in late April 2015, but peak adult emergence did not occur until the second week of May. This was followed by a larger frst-generation peak in early June, and a large second-generation peak in the frst week of July. ABW damage also oc - curred later in the growing season compared with the northeastern U.S., and was most se - vere in the frst week of August. Insecticide trials were conducted to evaluate the products currently recommended in North Carolina. Results from these trials were inconsistent with product effcacy, varying considerably by sampling date. Newer chemistries generally had a greater impact on weevil populations, but control was consistently below 80%. More research is needed to evaluate control products and application timing for this pest in North Carolina. Our 2015 research has confrmed that ABW biology and timing is affected by the difference in climate and en - vironmental conditions in North Carolina, and that the approaches used to manage ABW in the Northeast cannot be applied with the same success in the Southeast. — Terri Billeisen, Ph.D. (tlhoctor@ncsu.edu), and Rick Brandenburg, Ph.D., North Carolina State University, Raleigh, N.C. Teresa Carson (tcarson@gcsaa.org) is GCM's science editor. Photo courtesy of Ricardo Ramirez Photos by Matt Bertone

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