Reports of Injury Caused by Annual White Grubs

May 28, 1999
This year we have received several reports of injury to seedling corn plants caused by annual white grubs, including Japanese beetle grubs. Although in the past we have stated that annual white grubs cause little injury to corn seedlings, the events this year and last year suggest that we need to reconsider. Our previous statements were based on research conducted at Iowa State University. However, recent studies conducted at Purdue University reveal that annual white grubs, under some circumstances, can cause noticeable injury to corn seedlings. In the past, when corn was planted during May, for the most part, annual white grubs had almost completed their feeding by the time the seedlings had any size. However, now that planting begins in some areas of Illinois in late March and early April, corn seedlings are exposed for a longer period of time to annual white grubs that become active early in the spring.

If you encounter a white grub problem in a field, it's still a good idea to check out the types of grubs causing the injury. Refer to issue no. 2 (April 2, 1999) of the Bulletin for illustrations of the rear ends (rasters) of true white grubs, annual white grubs (grubs of the southern masked chafer), and Japanese beetle grubs. The arrangement of hairs on the raster will help you distinguish among the three types of grubs. If you have midsized true white grubs (3-year life cycle), you can anticipate grubs in the field again next year.--Kevin Steffey

Author: Kevin Steffey