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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

White Grub Management in the Spring

This article was published originally on 3/10/2000

The prolonged dry weather last fall lead to an abundance of white grub problems around the state. Many homeowners are contemplating what to do this spring to repair the damage and prevent its reoccurrence.

First, insecticide treatment in the spring is almost never warranted. While paying to apply (or have applied) more insecticide has a certain emotional appeal, it is unnecessary under most circumstances and terribly inefficient under the best circumstances. Grubs are full-grown in the spring. They don't die easily and control percentages are usually low. Simultaneously, grass growth is vigorous and damage symptoms from feeding by overwintered grubs are masked (un-apparent).

What to do

Repair areas of thin, damaged turf. Re-seed or re-sod the damaged areas after soil temperatures warm. Then follow a program of moderate fertility, mow at appropriate heights and intervals, and other proper steps to insure a healthy lawn. Consider white grub prevention with insecticides in mid to late summer.

There are 3 choices for grub management in the home lawn, depending on your tolerance for damage, comfort with pesticides and willingness to spend the cash.

  1. The Golf Course Approach: Treat every part of the lawn, every year because you might have white grubs and heavy use of high-price insecticide is preferable to ANY white grub damage. The available insecticides for preventive treatment are Merit, Grub-Ex and Mach 2. These must be applied before early August to prevent damage. A compromise modification of the Golf-Course Approach is to treat only those areas of previous damage. The risk obviously is that grubs may not repeat in exactly the same location as in the past.
  2. Wait-And-See Approach. Watch the lawn carefully during August - September for early signs of damage (wilting, turning brown). Apply the insecticide only where needed and when needed. The risk of the wait-and-see approach is that you might still lose some sod. If summer rainfall or irrigation keeps the grass growing and vigorous through July and August symptoms of white grub damage will be concealed and may not appear until after it is too late for effective treatment (late September through late October). Unfortunately, raccoons and skunks are much better at locating grub populations than we are and the first hint of a grub problem in your turf is likely to be that your lawn was "plowed" by varmints overnight.
  3. The Do-Nothing Approach. Count up how many years you DID NOT have grub damage. Divide the cost of replaced sod by that number of years. If the yearly-averaged cost of sod is less than the price of insecticide, do nothing and take your lumps in the occasional year when damage occurs. This approach is much easier to use if your attitude is "it's just grass, anyway."

White grub management decisions are difficult and frustrating. There is no one right answer for everyone.



This article originally appeared in the March 10, 2000 issue, p. 21.

Year of Publication: 
2000
Issue: 
IC-483(4) -- March 10, 2000