COLUMBIA, Mo.—Due to warm, humid days this spring, homeowners and lawn managers might notice an off-yellow or orange coloring of zoysia grass lawns, said a University of Missouri turf researcher.

Large brown patch, or zoysia patch, is a fungal disease that creates patches of discolored zoysia grass, leading to weed invasion, said Brad Fresenburg. No truly effective fungicides are available over the counter.

“Thatch management in zoysia will help reduce the potential for the disease,” Fresenburg said.

Thatch is a layer of decaying plant matter that accumulates in lawns between the soil and the grass blades. Excessive thatch can harbor disease-causing fungi and insects, and slow the movement of air, water and nutrients into the soil.

Zoysia grass is prone to thatch accumulation because of its thick network of rhizomes, stolons and coarse, tough stem tissue.

Lawns should be dethatched when thatch is more than a half-inch thick. Use a spring-tine power rake or vertical mower. If thatch is more than an inch thick, dethatch over a period of two or three years rather than all at once.

Consider intensive coring, which causes much less damage to the turf than does power raking or vertical mowing.

Control thatch buildup by moderate fertilizing, cutting grass regularly at recommended heights and watering deeply only when needed.

Standard zoysia grass maintenance is simple, Fresenburg said. Established zoysia grass needs less fertilizer than many other species of attractive turf. A seasonal two-pound application of nitrogen per 1,000 square feet is ample.

“Excessive or untimely fertilizer applications can lead to problems such as fewer roots, more thatch, diseases and more top growth, which requires increased mowing,” he said.

For best results, get soil tested before fertilizing. Slightly acidic soil pH is best. Apply lime only if the pH is less than 6.0. Fertilize established zoysia grass from May through August.

Mow zoysia grass at a shorter cutting height (1-2 inches) than Kentucky bluegrass or fescue. Never remove more than one-third of the leaf blade at any one time.

Zoysia grass requires less water than Kentucky bluegrass to remain green and actively growing during summer months. Watering is usually not needed except during prolonged dry periods.

For more information, see these MU Extension publications: