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...And the Heat Goes On....Summer Lawn Disease

© Georgeann Hall

Well, spring has become summer, but for many of us it has felt like summer since May. Many folks are already contending with high heat,drought, and humidity; three factors which will adversely affect plant growth.

When temperatures rise into the 90's, plant growth slows or even stops. This is quite evident in the cool season turfgrasses such as Kentucky bluegrass, perennial rye, and fescue. It is at this point of slowest growth that lawn diseases can gain a foothold.

I have included a description of the some of the most common summertime lawn diseases below.

Helminthosporium (Melting Out) Turf appears to mysteriously thin out. Close mowing will encourage this disease.

Puccinia (Rust) Grass blades appear to be covered with an orange powdery substance. The rust life cycle is actually a complex process due to the number of spore stages and types of hosts needed. Rust is more severe on underfed and closely mowed turf.

Rhizoctonia solani (Brown Patch) A soil borne fungus, this disease appears as circular patches of thinned or blighted grass. Early in the morning, a dark smokey ring may be noticed around the patches as well. Poor drainage and excess nitrogen will predispose turf to this disease. Removal of morning dew by lightly spraying will help prevent this disease.

Sclerotina homeocarpa (Dollar Spot) This fungal disease is active throughout the year, but periods of drought make it more severe as does inadequate fertilization. Removing the morning dew will help prevent this disease too.

Summer Patch (Magnaporthe poae) Previously called fusarium blight, appears as circular or crescent-shaped areas of dead turf sometimes with green centers. Conditions of high temperature and light will open turf to this disease.

The best way to manage any disease is to prevent it in the first place. Some good cultural practices to follow are:

Avoid monoculture. That is, avoid planting any one species of lawn grass. Try to have 2 or 3 species in the mix. Then if disease strikes, it is less likely to wipe out the entire lawn.

Apply compost. Topdressing every year with a thin layer of compost will encourage beneficial microoganisms. These microorganisms produce antibiotics which help control the disease.

Proper timing of irrigation. Water the lawn in the early morning or afternoon. This will ensure that the grass blades will have had time to dry before nightfall.

Remove guttation water. Guttation water is simply morning dew. This dew is rich in sugars and carbohydrates which support many fungal pathogens. Syringing the lawn will remove this water and help prevent disease.