Plant diseases can be problems for turf growing under stressful conditions. Sod field regrowth after harvest is a period when the turf is especially susceptible to rust diseases in the fall with some rain or heavy dew. The following series of photographs was taken at a sod farm on Saturday, September 8, in Western Colorado. The photos clearly demonstrate the severity of leaf rust under such conditions.

Severely infected turf is thin, and orange to yellow in color. Other rusts can cause turf to appear red or brown. Early symptoms of the disease appear as light yellow flecks on leaves or stems depending on whether the rust is a leaf rust or stem rust. Note that there are more that 34 reported rusts on turf grass types. These will vary depending on turf type, environment and location. Rust spots enlarge and elongate parallel to the veins in the stem or leaf. As the fungus matures, spores are produced which erupt through the leaf tissue creating pustules. These pustules are called uredia; the exposed spores are urediospores. The urediospores give the fungus its characteristic rust color, hence its name. Lawnmowers and other equipment used on rust infected turf will be coated with these rust-colored spores. Unless equipment is properly cleaned it can spread spores through the field.

The first two photographs show the color change of the turf resulting from the rust infection.

Turf should be provided proper care to avoid stress. This includes attention to water, fertilizer, and mowing frequency. When this disease is severe, clippings should be removed to reduce the production of urediospores. Optimal temperatures for growth of the rust fungus and urediospore production is between 20 and 30o C (68 - 86o F).

Fungicides reported to be effective against rust include Banner (propiconazole), Bayleton (triademefon), Fore (mancozeb), and Rubigan, Patchwork (fenarimol). Heritage (azoxystrobin) is labeled for rusts on turf and should be very effective, Brown used it on small grain rusts and found it was effective. The problem with this product is its cost and lack of availability to homeowners. Daconil (chlorothalonil) is also good if you can find it. It is being phased out of the homeowner market; there is even some concern chlorothalonil may be lost to other markets as well.

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