Biology, Ecology, and Management of White Grubs in North Carolina Turfgrass

Larval scarabs (Coleoptera: Scarabaeidae) known as white grubs, are an increasingly important pest of turfgrass in North Carolina. This research was conducted to gain knowledge of white grub ecology and develop a cost effective management program incorporating conventional insecticides and "non-traditional" control strategies for North Carolina turfgrass managers.;A 3-year statewide pheromone and blacklight trapping study was conducted to identify the seasonal activity, relative abundance, and distribution of key damaging species. The Japanese beetle, Popillia japonica, was present at all 9 trapping sites. Peak flight generally occurred 22 Jun -- 21 Jul. The oriental beetle, Anomala orientalis, was localized to Buncombe Co. in western North Carolina with activity peaking 22 Jun -- 7 Jul annually. Masked chafers (Cyclocephala spp.) represented 87.5 to 96.6% of species in blacklight traps in western trapping sites. Cyclocephala spp. flight peaked between 1 -- 21 Jul. Species of Phyllophaga were dominant in central North Carolina representing 33 -- 45% of species collected and exhibited peak flight in late July. The rice beetle, Dyscinetus morator made up 74 -- 84% of species at coastal sites and were active Jun to Jul. Anomala marginata, A. flavipennis, Pelidnota punctata, Tomarus gibbosus, Euetheola humilis rugiceps, Maladera castanea, and species of Polyphylla were routinely trapped. This study documents the occurrence of multiple species of injurious white grubs at most sites throughout North Carolina.;Small arena choice and no-choice tests and large cage choice tests were conducted to determine if P. japonica oviposition differed between tall fescue and bermudagrass. In three series of small arena choice tests, 82.5% of all eggs were laid in tall fescue cores. During the first small arena no-choice test, tall fescue cores received significantly more eggs than bermudagrass. A follow up no-choice test failed to detect similar variation. No preference for either species of turfgrass was detected in cage choice tests conducted with large numbers of beetles. Under moderate pest density in mixed turfgrass stands, tall fescue will likely receive more eggs from ovipositing P. japonica. The biological drive of females under no-choice conditions as well as high population pressure in the field however may override host plant criteria utilized by female beetles.;Commercial milky spore powder, SurroundRTM WP, and SulFer 95 were tested in multi-year field and greenhouse trials, as well as small arena and large cage oviposition assays as alternative management strategies. Milky spore failed to significantly reduce grubs in multi-year field trials and greenhouse experiments. SurroundRTM WP did not decrease grub numbers in field plots in 2007 but provided significant control in 2008. SurroundRTM WP was unsuccessful in deterring P. japonica oviposition in small arena and large cage experiments. Efficacy of SulFer 95 applied prior to and throughout adult beetle flight also varied significantly in field trials between years. Sulfer 95 did not impact female P. japonica oviposition in 2-way small arena and large cage choice tests. This study suggests that the efficacy of these products as alternative control measures is highly dependent on environmental conditions and interactions within the turfgrass environment which are not clearly understood.;High and low rates as well as multiple application timings of the neonicotinoid insecticides Arena 0.5G (clothianidin), Meridian 0.33G (thiamethoxam), Merit 0.5G (imidacloprid), as well as the combination product Allectus 0.36G (imidacloprid + bifenthrin) were evaluated for white grub control in multiple field trials during 2007 and 2008. Arena 0.5G and Meridian 0.33G provided significant control of white grub infestations in both years regardless of rate or application timing. Allectus 0.36G treatments significantly reduced grub numbers below control plots in 2007. Significant differences did exist between treatments, with late applications providing the least control. Allectus 0.36G treatments in 2008 reduced grub numbers significantly compared to control plots with no observed treatment differences. Merit 0.5G significantly decreased grub numbers in treated plots with the exception of late applications made in 2007.