Stripe smut is caused by the fungus Ustilago striiformis. It affects many common turf grasses, especially bentgrass and bluegrass. Kentucky bluegrass cv. Merion is especially susceptible. It is generally more of problem in established stands of turf than in newly seeded areas. It is often difficult to recognize this disease until the plants have been infected for at least 4 years, since the plants are usually scattered throughout the turf. This disease is favored by cool (50^o to 60^o F) weather, and is usually a problem in spring and fall.

Symptoms. Stripe smut may cause large patches in which most plants are infected. These patches may be up to 12 inches across. The disease can can also affect individual plants scattered throughout the turf. Affected leaves are pale green or yellow, and stiff, upright and stunted. Long, yellow-green streaks are produced on the leaves, running lengthwise between the veins. In time, these streaks will become gray, and will then split open to release black, dusty fungal spores. Soon after this, the leaf will turn brown, split, and curl from the tip downward and die. Severely infected plants may die in the heat of the summer, leaving irregular patches in the lawn.

Prevention.

• Plant disease-free seed and sod.
• Use seed mixtures that contain resistant varieties to prevent devastating epidemics.
• Allow grass to undergo natural summer dormancy so that the infected leaves will die. This may keep the spore production to a minimum, and decrease the number of future infections. Do this by withholding water and fertilizer during the hottest part of the summer.
• Avoid fertilizing excessively with nitrogen in the spring. It is important to apply a balanced fertilizer, though, to encourage vigorous growth, as this disease affects aging turf.
• See current recommendations for chemical control measures.

Rust is a disease that affects almost all turfgrasses. It is caused by fungi in the genus Puccinia. This disease is usually most severe on turf that is weakened from shade, drought, nutrient deficiency, or improper mowing. This disease is favored by low light, wet leaves, and temperatures of about 70^oF.

Symptoms. Light, yellow flecks on the leaves or stems become long, yellow stripes which are parallel to the veins. They will split open and spores will dust out. The spores range in color from orange to brick-red, although they can be yellow to brown or black for some rust species.

When the infection is severe, the entire area may appear the color of the spores, and the spores may cling to hands, clothing, or shoes. The turf may die in patches from the infection, or the stand may be thinned and weakened.

Prevention. In general, rusts cause less damage to turf when the grass is healthy and growing vigorously.

• Avoid water stress by irrigating during dry periods.
• Water early in the day to allow the leaves to dry before night.
• Prune trees and shrubs to allow better light penetration and air circulation.
• Avoid mowing lower than the recommended height, as this can lead to stunted root systems and decrease the ability of the turf to withstand drought.
• Mow regularly to remove leaves before the spores are produced.
• Use a balanced fertilizer at recommended levels, as low nitrogen levels and nutrient imbalance can encourage this disease.

Resistance is available to this disease. See current recommendations for chemical control measures.

By Pamela S. Mercure, IPM Program Assistant, University of Connecticut, 1998.

References.

Smiley, R.W. 1983. Compendium of Turfgrass Diseases. APS Press, St Paul, MN.

Smith, J.D., N. Jackson, and A.R. Woolhouse. 1989. Fungal Diseases of Amenity Turfgrasses, Third Edition. E.& F.N. Spon, London.

Turgeon, A.J. 1996. Turfgrass Management, Fourth Edition. Prentice Hall, Upper Saddle River, New Jersey.

This information was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.

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