University of Missouri Extension
COLUMBIA, Mo. – Brown patch is a fungal disease of turfgrass that loves two things: heat and moisture.
“I’ve noticed a fair amount of brown patch starting to develop over the past two weeks and with the wet weather and warm temperatures that we’re seeing now, we’ll see a lot more of it,” said Brad Fresenburg, turf specialist for University of Missouri Extension.
As the name implies, it shows up as a patch of grass that has turned brown. It kind of tricks the homeowner into providing what it needs.
“The biggest mistake often made is the homeowner will add water or fertilizer in hopes of improving those brown patches. They’re actually feeding the disease,” Fresenburg said.
Brown patch, which is caused by the plant pathogenic fungus Rhizoctonia solani, is considered a summer disease because it spreads rapidly in the heat.
“Dr. Lee Miller, our turfgrass pathologist, refers to the 6-8 Flip-Flop rule. If you’re at 86 degrees or higher during the day and 68 degrees or higher at night, that combination will bring on brown patch,” Fresenburg said.
So before you drag out the bag of fertilizer or the garden hose, take a close look at your grass.
“You will notice brown lesions on the leaf blade. It could be along the margins of the blade or in the center. It’s usually a straw- or tan-colored lesion that has a dark margin,” Fresenburg said.
If you’re still not sure, Fresenburg says you can take a sample to your local MU Extension office to confirm whether it’s brown patch.
You need to get it identified as quickly as possible, because brown patch will continue to spread throughout the growing season unless it stops getting moisture.
“Usually, it will stop if we get into drier conditions, especially if we get into drought conditions where the grass dries out and starts to go dormant,” Fresenburg said. “But, we often find when it starts to dry out, that’s when folks turn on the garden hose.”
There are treatments available, and Fresenburg said the best approach is often to hire a lawn care operator.