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Grub Larvae closeup

Japanese and Masked Chafer Beetle damage in the lawn


This summer, the return of beetles has been evident after an all-time low from the drought in 2012. Beetle numbers have climbed each year since then and this summer have a very strong presence again.

Female beetles are attracted to moist soils and locations where there will be plenty of food for their hatching eggs. We have had quite a bit of rain this summer, so finding moist soils is not a problem, and our green lawns will be providing the food. Statewide, the rains have been irregular, but around here, we have had to continue to mow consistently all summer.

Is there an up side to this? There sure is. Since we have had abundant rain, grass everywhere is green and the soils are moist, likely reducing the potential home lawn damage. This is in contrast to those summers where if you wanted a green lawn you had to water, and the beetles then found your home lawn to be the only game in town.

Just like in the garden, the lawn can sustain and recover from some insect damage. The magic number is 10 to 12 grubs feeding per square foot. More than that and the lawn cannot keep up with the loss of grass roots. Less than the 10 to 12 per square foot and you will not see damage.

By now, you should be able to find grubs in the lawn. If feeding is heavy, the impacted areas will lift up as if it were newly laid sod. Your also can see a difference, as it will not grow as well as the other areas in the lawn and will brown, especially when we go several days without rain or being watered. Grubs will move 2- to 3-inches deeper into more moist soil if the soil near the surface dries, so you may not see grubs when you lift the "sod."Stir the soil around a bit and you will find them.

If you find 10 to 12 grubs or more in a square foot, a treatment is justified. There are products available to the homeowner for application. Lawn care firms also can provide appropriate products through their services. To avoid killing our bees and other pollinators, do not apply systemic insecticides to lawns with blooming weeds.

Richard Hentschel is a Horticulture Extension Educator with University of Illinois Extension, serving DuPage, Kane and Kendall counties. Stay tuned to more garden and yard updates with "This Week in the Garden" on Facebook at facebook.com/extensiondkk/videos. The 2017 Kendall County Master Gardener Help Desk currently is open Monday, Wednesday and Friday from 9 a.m. to 12:30 p.m. at 630-553-5823 or at uiemg-kendall@illinois.edu.



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