HomeWHENWhen To Put Down Grubex

When To Put Down Grubex

Be sure the problem is grubs. Before doing anything, it is important to make sure the problem is grubs. In the last 10 years, the amount of European chafer damage to home lawns in southern Michigan has steadily decreased to the point where it is unusual now to find populations high enough to damage turf. However, as European chafers and Japanese beetles have spread northward, lawns and other low maintenance turf areas in much of the Lower Peninsula north of Lansing and in the eastern half of the Upper Peninsula are seeing more damage. The outbreak phase where turf damage is common may last five to 10 years.

If you see a dead patch, use a shovel to dig up a few Frisbee-size samples of turf around the bare spot to a depth of 2 inches and look for 0.75-inch long, C-shaped white grubs. These are most likely the larvae of European chafers if they are found in lawns without an irrigation system. European chafers can devastate a lawn with little warning because the adult beetles fly at dusk when they emerge in June and early July, and can easily be overlooked because their evening flight to mate and lay eggs occurs after sunset. European chafers are generally found in drier turf and their population levels will fluctuate depending upon how wet or dry the weather was the previous summer.

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European chafer grubs may be found in all locations in Michigan’s Lower Peninsula and in much of the Upper Peninsula. Regionally, European chafers are a much bigger problem than they used to be. In 2002, they were only found in New York, Pennsylvania, Massachusetts, Delaware, New Jersey, Connecticut, New Hampshire, Vermont, Maryland, Southern Michigan, and eastern Ohio. Now it has spread throughout Ohio, Michigan (all of the Lower and half of the Upper Peninsula), northern Indiana and into eastern Illinois. It was also reported in Wisconsin in 2013. In Canada, it is a problem in Ontario and Vancouver, so Washington State is on the lookout for it also.

Japanese beetle grubs also feed on turf roots in home lawns, but they are not usually as much of a problem on home lawns as European chafers can be. Japanese beetles and European chafers lay most of their eggs in July, but Japanese beetles continue laying eggs into August. Japanese beetles like to lay their eggs on irrigated turf like golf courses, athletic fields and highly maintained lawns. They can be abundant in non-irrigated home lawns if we receive frequent rain in July, but are scarce in lawns that are very dry in July and early August. We don’t seem to be getting as many calls about lawns damaged by Japanese beetle grubs in the southern half of the Lower Peninsula, south of Lansing, but we are getting more calls from the northern Lower Peninsula as Japanese beetles continue to spread northward. Wisconsin, Minnesota and Iowa have now joined the club of Midwest states with lots of Japanese beetles, and they have been found in isolated locations as far west as Colorado.

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Grubs in turf
Grubs found in turfgrass. Photo by Kevin Frank, MSU.
  • Check the bag or bottle to determine what active ingredient the product contains.
  • Do not use products containing ONLY lambda-cyhalothrin, gamma-cyhalothrin, bifenthrin, deltamethrin, cyfluthrin or permethrin for any phase of grub control.
  • Do not use preventive compounds such as clothianidin, thiamethoxam or imidacloprid now. Use them in June or July to control grubs that would be damaging turf in the fall. Applying them now will allow some of the chemical to leach through the turf or break down to the point that not enough insecticide will be there in July to control grubs.
  • The preventive compound chlorantraniliprole should ideally be applied in April or May to control grubs that would be damaging turf in the fall as it will take longer for the material to move to where the grubs will be feeding in July.
  • To kill grubs in the spring or fall, use carbaryl or trichlorfon.
  • Always wear rubber gloves and rubber boots when applying insecticides to turfgrass.
  • Make sure to irrigate the lawn with at least 0.5 inches of water* and allow the grass to dry before allowing anyone or pets into the treated area. Irrigation is essential for the chemical to be most effective.
  • Store insecticide products in a locked cabinet not accessible to children.
  • Proper fertilization is important to prevent and allow the lawn to recover from grub damage.
  • Mow lawns immediately before applying an insecticide for grubs to remove weed flowers and protect bees.

Make a regular practice of mowing your yard with the mower on the highest setting (3.5-4 inches).

*What is 0.5 inches of irrigation? A half-inch of irrigation is when lawn sprinklers are run until a container like a coffee mug, or several mugs, fills to a level 0.5 inches up from the bottom of the cup.

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Below is a short list of products now being sold for grub control as of May 22, 2020, in stores checked in the Mid-Michigan area. An online search indicates there are other products that will be available at other stores. Check the active ingredients.

Available preventive products

  • Scotts Grub-Ex – Granularchlorantraniliprole 0.08% Apply between April 1 and May 30 (no later than July 15) for best results.
  • Bayer Advanced Season-Long Grub Control (or Bayer Advanced Merit) – Granularimidacloprid 0.25%Apply between June 1 and July 15 for best results.
  • Bayer Advanced Season-Long Grub Control and Turf Revitalizer – Granularimidacloprid 0.25% and a low fertilizer rate (6-0-1) Apply between June 1 and July 15 for best results.
  • Premium Grub Control (Do not confuse with “Premium Insect Control”)imidacloprid 0.2% – Granular Apply between June 1 and July 15 for best results.
  • Bayer Advanced Complete Insect Killer Liquid attach-to-hose-bottlecyfluthrin 0.36% and imidacloprid 0.72% Apply between June 1 and July 15 for best results.
  • Bayer Advanced Complete Insect Killer Granules – Granularcyfluthrin 0.05% and imidacloprid 0.15% Apply between June 1 and July 15 for best results.

Available curative products

  • Sevin Lawn Insect Granules – Granularcarbaryl 2.0% Apply in September or October to active grubs.
  • Bayer Advanced 24 hr Grub Killer Plus – Granulartrichlorfon 9.3% Apply in spring or fall to active grubs.

Products that will NOT kill grubs

  • Spectracide Triazicide Insect Killer for Lawns – Granulargamma-cyhalothrin 0.05% This product will not kill grubs at any rate. This product was tested by MSU for grub control in 2006 and gave identical results as the untreated plots.

This material is based upon work supported by the USDA and the National Institute of Food and Agriculture award number(s) 2014-70006-22498.

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