Grubs in the Lawn  

In Michigan, the most destructive white grubs found in lawns and gardens are the larvae of Japanese Beetles and the European Chafer. White grubs have C-shaped bodies approximately 3/4 inch - 1 1/2 inches in length.  They live in the soil and feed on plant roots which weakens and may eventually kill plants. 

              Adult Japanese Beetle                                   Adult European Chafer (Common June Bug)

Does your lawn have grubs?  Here are the symptoms...

Small, dried out and dying patches of grass, which may peel back like a carpet, indicate a possible grub problem. The presence of skunks or moles is not always a sign of a grub problem as these animals also eat other soil organisms such as worms.

A simple test to tell...

The ideal time to look for grubs is mid April to early May, and mid to late August. Cut through three sides of a 1-square-foot flap of sod. Roll the flap back to look underneath. Loosen soil to a depth of 2” to 4”. Count the grubs. Return flap to position and water well for 1 - 2 weeks to allow grass to re-root. To be sure you have a problem, repeat this in a few locations.  If you do not water your lawn frequently, five or more grubs per square foot indicates a grub problem. Twenty or more grubs per square foot may be a serious problem in a well-watered lawn.

Lifecycle and effective treatment timing...

Grubs overwinter and begin feeding early in the spring (usually April/May).  Grubs pupate and become adult beetles around late spring through early summer. The next generation begins in mid summer after female beetles lay their eggs in the lawn. In mid-August, these eggs hatch and the larvae (grubs) feed on grass roots throughout autumn.  Proper timing of any grub control treatment is essential for success.  Application time varies with each product. Some products need to be applied early to mid-July, prior to the grubs hatching; Other products need to be applied in the larval stages (when the grubs are present) in order to be effective.

Grub Control Options

There are usually several management options for solving any pest or disease problem. Use the non-pesticide approach whenever possible, saving pesticide use as the last line of defense. If a pest is identified at a damaging level, select a control targeted to the problem. This is called “Integrated Pest Management” or “IPM”.

Prevention

The best way to save a grub-infested lawn is to properly irrigate. Daily watering promotes grass growth and counteracts root damage caused by grubs. Maintaining a healthy lawn will allow it to better withstand grub attack.

Chemical Controls

If you decide to use a chemical treatment, consider the life cycle of the pest in determining the proper timing of the application.  There are a number of chemical options. See “Precautionary Statements" on package label for toxicity information.

This information is brought to you by D.A. Alexander & Company, Inc. (877) 427-0030.

Sources of information:

Metropolitan Detroit  Landscape Association

Michigan Department of Agriculture

MSU Extension - Oakland County

SOCWA -Southeastern Oakland  County Water Authority, Healthy Lawn Program, Garden Tip Sheets

Greg Patchan, Horticulture Agent, Oakland County MSU Extension.

EIlis and Landis. What’s Bugging You?, MSU Extension Bulletin E-2649

Otkowski, et. al., Common-Sense Pest control, Taunton Press

Photos: Dan Potter, University of Kentucky Entomology. Beetle life cycle diagram: J. Kalisch, University of Nebraska

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