Spatial analysis of the association between the annual bluegrass weevil and susceptible golf course turf

The annual bluegrass weevil (Listronotus maculicollis) (ABW) is a destructive pest of close-cut turf in golf courses of the Northeast. The insect causes die-off of its host plant, Poa annua L., in summer along the perimeter of fairways and putting greens, degrading playability and aesthetic quality. Larval stages that feed on stems and crowns of the host plant have been determined as the root cause of injury expression; however, previous studies have not supported consistent association between larval density and injury severity. In order to better correlate injury expression to larval presence, we investigated the spatial associations among insect density (adult and larva), host plant density and habitat variables (soil moisture, soil nutrients, thatch depth, etc.). Spatially-explicit data from a golf course fairway over 2 yr were analyzed by SADIE (Spatial Analysis by Distance IndicEs). Injury expression was significantly associated with larval density, thatch depth, and soil nitrate concentration, while injury expression was significantly dissociated with host plant density. The results show injury expression due to larval feeding becomes more severe under conditions of deep thatch and high soil nitrate concentration. While no cultural control tactics are currently used for ABW injury suppression, we propose that agronomic practices affecting thatch accumulation and nutrient balance should be explored for ABW management on golf course turf.