Influence of Feeding by Grubs of the Southern Masked Chafer on Quality and Yield of Kentucky Bluegrass12

Abstract

Grubs of Cyclocephala immaculata (Olivier) are serious pests of turfgrass in home lawns, golf courses, parks, and other urban areas. To measure the impact of larval feeding on Kentucky bluegrass turf, sunken enclosures were infested with 3rd instars of the southern masked chafer at densities of 0 to 48 grubs per 0.1 m2. On the basis of visual ratings and clipping weights, initial densities of 24 to 48 grubs per 0.1 2 caused significant reductions in quality and yield after only 2 weeks, and reduced growth by up to 65% after 6 weeks of feeding. Regular irrigation or adequate rainfall masked differences between infested and uninfested plots. Apparently, in many situations, the economic threshold for masked chafer grubs is considerably higher than the usual rule-of-thumb estimate of six to eight grubs per 0.1 m2.