But chlorantraniliprole takes 60 to 90 days to become effective, so the best time to apply this product is from late April through early June, in a single application.
This is a little different from the timing for imidacloprid, the other choice for homeowners. Applying this product too soon is a waste, since you’ll have to reapply it. The best time to make your single application of imidacloprid is in June or July. New research is showing it can be applied into August as well.
There is a third product on the shelves with the active ingredient trichlorfon, sold as 24 Hour Grub Control. This is much more toxic than the other two options and kills grubs for only a 24-hour window of time. If you choose this product, wait until you find young grubs in your lawn in late summer, and make the application then. If grubs are not present, it will be a waste.
None of these products is effective on the large grubs you are finding right now. Those are the older larvae from last year’s hatch, and they are just about to pupate and become adult beetles. At this late stage, they are very resistant to insecticides. You are better off reseeding bare areas in your lawn now and treating with the less-toxic products to control the next generation as it hatches out in late summer.
Grubs are a complicated problem. For a free, updated fact sheet about white grubs and your control options, contact our office at 561-7450 or email Jolene Wallace at email@example.com.
PESTICIDE DISCLAIMER: Every effort has been made to provide correct, complete and up-to-date pesticide recommendations. Nevertheless, changes in pesticide regulations occur constantly, and human errors are still possible. These recommendations are not a substitute for pesticide labeling. Please read the label before applying any pesticide, and follow the directions exactly.
Amy Ivy is executive director of Cornell Cooperative Extension, Clinton County. Office phone numbers: Clinton County, 561-7450; Essex County, 962-4810; Franklin County, 483-7403. Website: www.cce.cornell.edu/ecgardening. Email questions to askMG@cornell.edu.