TURF SCIENCE


Late-Season Grub Control

Act now to discourage grub predators from tearing up clients' lawns
By Ken Kukorowski


Whenever you defend your turf - and in this case literally defend your turf - it's often wise to first size up or understand your adversary.

White grubs (the larvae of a particular group of Scarabaeidae beetles) are still the number one turf pest in the United States. While we sometimes think that the predominant grub pest today is the Japanese beetle, there are at least eight other species of similar scarab beetles (grubs) we need to worry about.


The larvae of the Japanese beetle are one of several species of white grubs. These white, Cshaped larvae feed on the roots of grasses and attract turf-damaging predators.
PHOTO BY JOHN A. WEIDHASS, VIRGINIA POLYTECHNIC INSTITUTE AND STATE UNIVERSITY, .

These various species of grubs share many similarities. They all have a characteristic white C-shaped larval body; all start their life cycles at various times mid-summer, and most emerge as adults about 10 months later; and all feed in the ground on turf roots, as well as on organic matter in the soil. The damage they cause from root pruning is magnified when the weather gets hot and dry and the remaining root system cannot keep up with transpiration demands. Except for the feeding that Japanese beetle adults do, most other scarab beetle adults cause little to no feeding damage. Female scarab adults lay their eggs in places where they feel the eggs have the best chance for survival, so well-maintained turf is a prime oviposition spot.

Grub control used to be complicated before the early preventative control insecticides like imidacloprid (Merit), clothianidin (Arena) and chlorantraniliprole (Acelepryn) made their impact on the market. These grub active insecticides can be applied to turfgrass within a very wide application time window (usually April or May through August) and their residual properties provide control of the early stage grubs quickly, but definitely before the grubs grow in size and become voracious root feeders.

But, with all the tasks that need attention in April through August, what happens if you forget your preventative grub treatment? Obviously, if your turf attracts grubs, they will feed on the luscious roots, pruning them, and with just a little stress, the turf will die. Worse still, as these grubs grow in size, predators like raccoons, skunks and birds will feed on them, often "rototilling" your managed turf to uncover the grubs. This turf damage will require considerable money and effort to restore.

There are curative grub control products that can be applied to the turf at this time (late August through October) that will control the grubs in as little time as one to three days. Without active grub feeding in turf, most predators do not detect grubs in the turf and they look elsewhere for their meals. Curative grub control products work much faster on existing grubs and provide little-to-no residual insecticide control.

One leading product is Dylox, which contains trichlorfon. Once watered into the turf, it begins working immediately to kill grubs. At this time, the grubs are usually third instar (the maximum size for the first summer before winter resting), which is the hardest stage to control, but trichlorfon often reduces the population by 70 percent (sometimes more than 70 percent).

This dramatic reduction eases the root pruning, and thins the food population for predators, causing them to look elsewhere for food. As the predators leave your turf, the damage they cause also departs, leaving you to begin your late fall, early winter turf maintenance program.

Ken Kukorowski is senior research scientist specializing in insecticides, and head of research and development (R&D) for the Environmental Science division of Bayer CropScience LP. Prior to joining Bayer, he accumulated more than 20 years of industry experience specializing in R&D and technical development, with a focus on insecticides. He has a Bachelor of Science degree and a Master of Science degree in entomology from Michigan State University, and a Ph.D. in entomology from the University of Wisconsin-Madison.