Tolerance of Cool-Season Turf grasses to Feeding by Japanese Beetle and Southern Masked Chafer (Coleoptera: Scarabaeidae) Grubs

Abstract

Response of Kentucky bluegrass, Poa pratensis L.; tall fescue,Festuca arundinacea Schreber; hard fescue, F ovina L. var. duriuscula; perennial rye grass, Lolium perenne L.; and creeping bent grass, Agrostis palustris (Hudson), to herbivory by root-feeding by grubs of Japanese beetle, Popillia japonica Newman, and southern masked chafer, Cyclocephala lunda Bland, was evaluated in greenhouse trials. Potted turf grasses were infested with initial densities equivalent to 73 or 146 grubs per 0.1 m2 in spring and fall trials, and effects on plant growth and grub survival were determined. All turf grasses tolerated significant damage to roots without loss of foliage yield. In fact, feeding by grubs stimulated increased growth of foliage in some grasses. With comparable densities of grubs, loss of roots tended to be proportionately less in creeping bent grass than in other grass species. Survival of grubs was similar in all turf grasses, and between low and high grub densities. P. japonica caused greater loss of roots than C. lurida in the spring trial, but the reverse was true in the fall. Root loss per grub decreased with increasing larval density, suggesting food limitation even though root systems were not completely devoured. Implications of these findings for tolerance and recovery of grub-damaged turf grasses are discussed.