Billbug Species Composition and Life Cycle on Missouri Zoysiagrass Fairways.

Billbug (Sphenophorus spp.) damage on zoysiagrass (Zoysia japonica Steud.) golf course fairways is becoming an emerging issue in Missouri and surrounding states. Among all billbug species, it is believed that hunting billbug (S. venatus vestitus Chittenden) is the main species that attacks warm-season turfgrass species including zoysiagrass. At the University of Missouri, we revealed a mixed population of bluegrass (S. parvulus Gyllenhal) and hunting billbugs that co-exist on zoysiagrass turf. The objective of this research was to characterize the phenology of billbugs on zoysiagrass fairways, in order to optimize selection of an effective insecticide as well as application timing. Beginning in April 2015, 40 pitfall traps were installed 3 meters apart on each of two zoysiagrass fairways, the 7^th fairway of Columbia Country Club (CCC) and the 17^th fairway of Country Club of Missouri (CCMO), in Columbia, Missouri. Pitfall traps were installed below ground, allowing a permanent collections over two growing seasons. Pitfall traps were monitored weekly during this experiment, and collected specimens were identified in the laboratory. Results indicated a distinct difference in billbug species composition at the two sites. Despite the same turf species and cultivar (‘Meyer’) on the two fairways, billbugs collected from CCC revealed a mixed population of both bluegrass and hunting billbugs, where the dynamics of population composition varied between 50:50 and 100:0 for hunting and bluegrass billbugs, respectively. In comparison, hunting billbugs dominated the specimens collected from CCMO throughout the year. It is to be determined why such a disparity in species composition exists. Our results also demonstrated two adult peak activities for hunting billbugs in spring and early fall, suggesting hunting billbugs likely go through 1.5 or 2 generations per year. These findings indicate that two insecticide applications might be necessary where hunting billbugs are the dominate species.