Full TGIF Record # 19488
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Publication Type:
Author(s):Clark, John D.; Potter, Daniel A.
Title:Competition between and relative feeding impact of masked chafer and Japanese beetle grubs: Confounding effects of a parasite
Source:Kentucky Turfgrass Research. 1986, p. 34-35.
Publishing Information:Lexington, KY: University of Kentucky, College of Agriculture, Cooperative Extension Service
Series:Progress Report 303
Keywords:TIC Keywords: Cyclocephala lurida; Cyclocephala borealis; Field tests; Popillia japonica; Parasites; Vespidae; Insect predators; Biological control; Laboratory tests; Grubs; Injuries; Competitive ability
Abstract/Contents:1986 study which compared relative feeding impact and competitive ability of Japanese beetle and masked chafer (Cyclocephala spp.) grubs. Ninety-six metal hoops, each enclosing 1 sq. ft., were driven 5 inches into the ground. Hoops were infested with either 0, 4, 8, 16, 32, or 64 late second or third instar grubs of one species or the other, or with equal numbers of both species so that the combined densities were as above. When the experiment started (late Aug.) the turf was mowed to a uniform height. Clippings were harvested after 5 and 10 weeks, oven dried, and weighed as a measure of yield. Hoops were removed at the end of the experiment and surviving grubs were counted and weighed. In a laboratory experiment, the relative aggressiveness of the two species was determined by the number of times that grubs of each species bit conspecifics or grubs of the other species. Japanese beetles were found to be much more aggressive than masked chafer grubs in the laboratory trials. Competition between the grubs could not be determined in the field experiment due to a high rate of parasitism within the hoops. A parasitic wasp (tentatively identified as Scolyiidae) selectively killed more than 90% of the masked chafer grubs in some hoops. This appears to be the first demonstration of a grub population being reduced below damaging levels by an insect parasite. The biology of this parasite will be investigated more fully in 1987. Japanese beetle grubs ap peared to be the more damaging of the two species, reducing grass yields by about 33% at densities of 40-50 grubs/sq.ft. Masked chafer grubs caused little measurable damage at similar densities. Economic injury thresholds for white grubs appear to be much higher than the usual rule-of-thumb estimate of 6-8 grubs/sq.ft.
ASA/CSSA/SSSA Citation (Crop Science-Like - may be incomplete):
Clark, J. D., and D. A. Potter. 1986. Competition between and relative feeding impact of masked chafer and Japanese beetle grubs: Confounding effects of a parasite. KY. Turfgrass Res. p. 34-35.
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