Converting a pest into a beneficial: Using the annual bluegrass weevil to suppress annual bluegrass in creeping bentgrass fairways

Using the golf course pest, annual bluegrass weevil (ABW), to control the weed, annual bluegrass, can reduce chemical applications. Previous research determined that ABW provides effective annual bluegrass control but was more effective with reduced annual bluegrass cover. We conducted two field experiments to study the impact of annual bluegrass cover on the effectiveness of ABW to control annual bluegrass without unacceptable losses in turf quality. In Experiment 1, we evaluated the effect of three insecticide programs (untreated, threshold-based, and preventive) at four percentages of initial annual bluegrass cover (0%, 10%, 25%, and 50%) on annual bluegrass cover and turf quality. In Experiment 2, using only the threshold-based program, we evaluated the effect of the same percentages of initial annual bluegrass cover on the reduction of annual bluegrass cover and turf quality. Annual bluegrass cover declined over the season, more intensely with high initial annual bluegrass cover and in spring when weevil damage was most severe. During the spring, high annual bluegrass cover led to limited and transient declines in turf quality. In Experiment 1, untreated and threshold-based programs reduced annual bluegrass cover in the second year, indicating that ABW provided control of annual bluegrass. In Experiment 2, only plots with high initial annual bluegrass cover received enough ABW damage to warrant threshold-based applications. The threshold-based insecticide program can reduce annual bluegrass cover with limited reduction in turf quality and is viable for annual bluegrass control with an initial annual bluegrass cover of at least up to 30%.