Billbug species composition on Missouri zoysiagrass golf course fairways

In recent years, billbug (Sphenophorus spp.) damage on zoysiagrass (Zoysia japonica Steud.) golf course fairways in Missouri and surrounding states has become an emerging problem. There are at least nine billbug species that attack turfgrass plants in the United States. Among them, bluegrass billbug (S. parvulus Gyllenhal) and hunting billbug (S. venatus vestitus Chittenden) are considered the most widely distributed species. Despite our belief that bluegrass billbug mainly attacks Kentucky bluegrass (Poa pratensis L.) and hunting billbug prefers warm-season turf including zoysiagrass, recent reports including experiment conducted at the University of Missouri revealed a mixed population of bluegrass and hunting billbugs that infest zoysiagrass turf. Therefore, the objective of this research was to monitor the phenology of billbugs on zoysiagrass fairways, in order to develop recommendations for optimum insecticide selection and proper application timing. Two experimental sites were established on zoysiagrass fairways at Country Club of Missouri (CCMO) and Columbia Country Club (CCC) in Columbia, MO. On each fairway, a total of 40 pitfall traps were installed at 3 meters apart on the ground below the soil surface. Adult billbugs were collected from these traps every week starting in April, and their counts and identification to species were recorded in the laboratory. Our results found a distinct difference in billbug species composition from these two fairways. Despite the same turf species and cultivar (‘Meyer’) on the fairways, specimens collected from CCMO were dominated by hunting billbugs, but samples collected from CCC indicated a mixed population of hunting and bluegrass billbugs. The dynamics of the billbug population from CCC varied from 50:50 to 100:0 for hunting and bluegrass billbugs, respectively, from spring to late summer in 2015. It is yet to be determined the cause of such a disparity in billbug composition at these two fairways.