Tuesday, May 26, 2015
White Grub Control Alternatives
Monitoring, one of the keystones of IPM is not practical for white grubs under most circumstances. Inspection for grubs requires cutting and lifting flaps of turf and looking for grubs below the thatch level. This is difficult, time consuming and potentially damaging. Research has indicated that the number of samples necessary is too large to be practical.
Studies at Cornell University have shown that over 70 percent of all grub control treatments were applied needlessly because there were no grubs in the lawn. Many homeowners are frightened into applying grub controls because of advertisements on TV, in plant centers, or because of horror stories they have heard about grub damage. Most grub treatments are not only expensive but hard to justify from an environmental standpoint.
There are 3 approaches to 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 grub prevention are imidacloprid (Merit®, Grub-Ex®) and halofenozide (Mach 2®, Grub-B-Gon®). 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. Grubs tend to return to the same areas in successive years, so it is logical to treat the areas where you had grubs last year or the year before.
#2. Wait-And-See Approach. Watch the lawn carefully during August - September for early signs of damage (wilting, turning brown). Apply a curative insecticide such as trichlorfon (Dylox, Bayer Advanced 24-Hour Grub Control) only where needed and when needed. The risk is that you might still lose some sod, especially if summer rainfall or irrigation keeps the grass growing and vigorous through July and August. Damage symptoms 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 follow 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.