Dosage response mortality of Japanese beetle, masked chafer, and June beetle (Coleoptera: Scarabaeidae) adults when exposed to experimental and commercially available granules containing Metarhizium brunneum

Authors: Behle, Robert; Goett, Erica

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2016
Publication Date: 5/2/2016
Citation: Behle, R.W., Goett, E.J. 2016. Dosage response mortality of Japanese beetle, masked chafer, and June beetle (Coleoptera: Scarabaeidae) adults when exposed to experimental and commercially available granules containing Metarhizium brunneum. Journal of Economic Entomology. 103(3):1109-1115. doi: 10.1093/jee/tow080.

Interpretive Summary: Scarab beetles are the adult stage white grubs, an important pest complex of turfgrass. Experimental and commercial biopesticide formulations containing the beneficial fungus Metarhizium brunneum were shown to cause infection of the adult beetles, representing an added benefit of pest control for treatments applied to target white grubs. Infection of the adults may reduce the numbers of eggs laid in the soil and reduce damage by the subsequent generation of grubs. These fungal based biopesticides are intended for application to the urban turf environment where there is a relatively high potential hazard for human exposure and ground water contamination by the miss application of chemical pesticides. These results will support commercial development of cost effective production of insect pathogens as biopesticides, expand the use of biological control as a replacement for chemical insecticides, and reduce the chemical pesticide load in the environment.

Technical Abstract: Adult beetles of three different white grub species, Japanese beetle, Popillia japonica, June beetle, Phyllophaga spp., and masked chafer, Cyclocephala spp. were exposed to experimental and commercially available granules containing Metarhizium brunneum (Petch) strain F52, to determine susceptibility of the beetles to this entomopathogenic fungus. Experimental granules contained microsclerotia produced by liquid fermentation, which produce fresh conidia when granules re-hydrate, were compared with commercial product (Met 52 ® granular bioinsectide), containing conidia produced by solid-substrate fermentation. When placed in cups containing moist potting mix treated with granules, all three species showed a positive dosage response to the fungus. LC50 values for field collected adults were 1.9 x 10**7 conidia cup**-1 for P. japonica, 7.1 x 10**6 conidia cup**-1 for Phyllophaga and 3.2 x 10**6 conidia cup**-1 for Cyclocephala. Adult beetles exposed to Met 52 granules had higher LC50 values: 5.9 x 10**7 conidia cup**-1 for Popillia japonica, 5.1 x 10**7 conidia cup**-1 for Phyllophaga and 7.6 x 10**6 conidia cup**-1 for Cyclocephala. The experimental granules containing microsclerotia show promise as a viable commercial control agent. They can be produced using lower cost fermentation methods and applied in at lower dosages (90 g for 1000 ft**2 as opposed to 454 g per 1000 ft**2 for Met 52). If granules are applied to control white grubs, adult beetles of P. japonica, Phyllophaga spp. and Cyclocephala spp. are susceptible to infection by the fungus and may become infected as they enter the soil to lay eggs.