Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2015
Publication Date: 7/2/2015
Citation: Behle, R.W., Richmond, D.S., Jackson, M.A., Dunlap, C.A. 2015. Evaluation of Metarhizium brunneum F52 (Hypocreales: Clavicipitaceae) for control of Japanese beetle larvae in turfgrass. Journal of Economic Entomology. 108(4):1587-1595. doi: http://dx.doi.org/10.1093/jee/tov176.
Interpretive Summary: The Japanese beetle, an important pest of turfgrass, was controlled by applications of experimental biopesticide formulations of the beneficial fungus Metarhizium brunneum. Production of biopesticides tends to be expensive and limits commercialization efforts. Advances in fermentation production of this fungus make it more economical to produce fungal structures for specifically targeting soil inhabiting insect pests. We first determined the insecticidal activity of the fungus against Japanese beetle larvae in the laboratory, and then demonstrated levels of control that were as good as commercial biopesticides and some chemical insecticide applications when targeting larger larvae later in the fall. 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: Experimental and commercial preparations of Metarhizium brunneum strain F52 were evaluated for control of Japanese beetle Popillia japonica Newman (Coleoptera: Scarbaeidae) larvae (white grubs) in the laboratory and under field conditions. Experimental preparations consisted of granule and liquid formulations made using in vitro produced microsclerotia, which are intended to produce infective conidial spores after application. These formulations were compared against the commercial insecticides imidacloprid and trichlorfon, and granular and liquid commercial formulations of M. brunneum F52 (Met 52) containing only conidia. Field collected white grubs were susceptible to infection in a dosage dependent relationship when exposed to potting soil treated with experimental microsclerotia granules in the laboratory. The LC50 for field-collected larvae was 14.2 mg of granules per cup (approx. 15 g granules m**-2). Field plots treated with M. brunneum F52 after September 10 (targeting 2nd and 3rd instar white grubs) had significantly lower white grub densities compared with untreated plots, providing 38.6 - 69.2% control. Levels of control attained by later applications of M. brunneum F52 sometimes equaled levels of control provided with the chemical insecticides. Treatments made prior to August 21 provided 14.3 - 69.3% control although white grub densities resulting from these treatments were often not significantly lower than those in untreated control plots. By comparison, chemical insecticide treatments provide 68 to 100% grub control, often providing better control when applied earlier in the season. In conclusion, P. japonica larvae are susceptible to infection by M. brunneum, and grub densities were reduced most consistently by fall applications targeting later instars.