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Leaf Spot — Bipolaris sorokiniana
© 2012 MSU Plant Pathology
© 2012 MSU Plant Pathology
© 2012 MSU Plant Pathology
Symptoms first appear as small dark purple to black colored spots on the leaf blade. As the spots enlarge, the centers often turn light tan. In warmer temperatures (> 85° F), the entire blade often appears dry and straw colored. The disease is mostly confined to the leaf blades during the cool weather, but can infect leaf sheaths, crowns and roots during hot, humid weather.
Leaf spot is a warm-weather disease, but the pathogen overwinters as dormant mycelium in infected plants and dead grass debris. Leaf spot can become evident when temperatures reach 70° F (21.1° C). The disease is most severe when temperatures are above 90° F and humidity is high. Conditions of drought stress followed by rewetting intensify the disease.
Symptoms first appear as small dark purple to black colored spots on the leaf blade. As the spots enlarge, the centers often turn light tan. In warmer temperatures (> 85° F), the entire blade often appears dry and straw colored. The disease is mostly confined to the leaf blades during the cool weather, but can infect leaf sheaths, crowns and roots during hot, humid weather.
Leaf spot is a warm-weather disease, but the pathogen overwinters as dormant mycelium in infected plants and dead grass debris. Leaf spot can become evident when temperatures reach 70° F (21.1° C). The disease is most severe when temperatures are above 90° F and humidity is high. Conditions of drought stress followed by rewetting intensify the disease.
Also Known As...
- Location:
» Home, Golf Course
- General Symptoms:
» Spot, Wilted
- Foliar Symptoms:
» Spots, Brown
- Time of Year:
» May, Jun, Jul, Aug, Sep
- Irrigated:
» Yes, No
- Hosts:
» Kentucky Bluegrass, Perennial Ryegrass, Tall Fescue, Fine Fescue, Creeping Bentgrass, Annual Bluegrass, Colonial Bent
When leaf spot is active, nitrogen levels should be kept moderate to avoid overstimulation of growth. Light, daily, midday irrigation applications, avoiding drought stress when the pathogen is active, will help to reduce or even prevent development of the disease. Avoid irrigation during the late afternoon and early evening during summer months. Genetic resistance to leaf spot exists in newer varieties of Kentucky bluegrass. These cultivars can be used to overseed damaged areas.
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- Chemical Control of Turfgrass Diseases 2011
University of Kentucky College of Agriculture
Turfgrass hosts include but are not limited to: Annual bluegrass, Kentucky bluegrass, fine-leaf fescues, tall fescue, colonial bentgrass, creeping bentgrass, and perennial ryegrass.
