Patches of dead grass

Asked April 18, 2017, 4:27 PM EDT

I thought my lawn was healthy last autumn but this spring there are scattered areas (~6 to 10 inches) were the grass is brown and apparently dead. Last year I dug into some of these and found a few white grubs that I assumed were cutting the dead grass from the roots. I did nothing to control the grubs. Is it likely my lawn has the same problem again? and what should I do (and when) ?

Ramsey County Minnesota lawns and turf lawn grubs horticulture

1 Response

Thank you for the question. It's hard to say what caused brown patches in your lawn last fall or this spring. Insects, disease, winter kill, or even salt or pet urine can cause this problem. It's true that Japanese beetle grubs feed on turf grass roots but a typical well watered and fertilized Kentucky bluegrass lawn can usually survive this. In non-irrigated lawns, grub populations of 7-15 per square inch can cause significant problems. The dead areas can often be rolled back because of the root destruction. When scouting for grubs, be sure to look for them in the green, living parts of your lawn but note that they may still be too deep in the ground to find them now. They will start to feed again when the soil warms.
Please read our publication on Japanese beetles. http://www.extension.umn.edu/garden/insects/find/japanese-beetles/ It is important to accurately identify your problem before treating for best results and to avoid use of unnecessary products that harm beneficials.
If you like you can use our self diagnostic program to explore other causes of turf problems: http://www.extension.umn.edu/garden/diagnose/plant/

Thank you for contacting Extension.