Golfdom, February 2015

the need for multiple applications to avoid damage Combined approaCh In the past ABW was successfully managed with one insecticide application However whether because of increased stress placed on the turf by modern cultural practices or because of pesticide insensitivity many courses require multiple insecticide applications in spring In areas with high ABW pressure a sequential application adulticide fol lowed by larvicide may be required A summary of university trials conducted over 20 years has indicated that adulticides lead to greater numerical reductions than larvicides Koppenhöfer et al 2012 However even with a properly timed adulticide against a pyrethroid susceptible population the range of control may vary between 60 percent and 90 percent Terefore in dense populations the survivors may be capable of producing enough larvae to cause damage Te combined approach allows for increasing the safety net in control though it may be rendered useless by a poorly timed application It should be stressed that the larvicide application of the combination approach may not be warranted and should only be applied if sampling reveals that the larval population has exceeded thresholds Damage appears for a multitude of reasons including drought stress trafc and turfgrass species In a study of mixed annual bluegrass creeping bentgrass fairways we found that pure Poa annua plots were 10 to 15 times more susceptible to damage than creeping bentgrass McGraw and Koppenhöfer 2009b Courses that are predominately Poa annua may beneft from sequential applications to keep larval densities lower than currently recommended thresholds What to take home Tere are strong arguments for all three management phi lo sophies Before formulating your ABW management plan please realize that 100 percent control of a population is not feasible Even the best products applied at the best possible times wont control every insect Successful control should be defined as maintaining weevi l densities that do not cause man vs abw visible damage with the fewest applications possible Ide a l l y di f fe rent approaches are needed for diferent areas based on past history of damage stress and turfgrass species In areas where some damage may be tolerated a single preventive or curative application is enough when scouting has determined that weevils are present in damaging numbers No two ABW populations are identical and because of the stresses imposed on the turf and chemical use history diferent populations will not respond the same to similar controls Taking the time to scout populations and understand the biological basis for timing products will lead to higher levels of control with fewer wasted applications Ben McGraw Ph D is an associate professor of turfgrass entomology at The Pennsylvania State University He can be reached at bam53@ psu edu References Koppenhöfer A M S R Alm R S Cowles B A McGraw S Swier and P J Vittum 2012 Controlling annual bluegrass weevil Optimal insecticide timing and rates Golf Course Management March 2012 98 104 McGraw B A and A M Koppenhöfer 2009a Population dynamics and interactions between endemic entomopathogenic nematodes and annual bluegrass weevil populations in golf course turfgrass Applied Soil Ecology 41 77 89 McGraw B A and A M Koppenhöfer 2009b Development of binomial sequential sampling plans for forecasting Listronotus maculicollis Coleoptera Curculionidae larvae based on the relationship to adult counts and turfgrass damage Journal of Economic Entomology 102 3 1325 1335 McGraw B A and A M Koppenhöfer 2010 Spatial distribution of colonizing Listronotus maculicollis populations implications for targeted management and host preference Journal of Applied Entomology 134 275 284 Ramoutar D S R Alm and R S Cowles 2009 Pyrethroid resistance in populations of Listronotus maculicollis Coleoptera Curculionidae from southern New England golf courses J Econ Entomol 102 388 392 fiGure 5 First generation larval feeding damage may often be severe on the edges of rough short mown borders Damage expression is influenced by many factors including larval density turfgrass species and plant stress February 2015 Golfdom 49 Golfdom com