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Purple Lawn Fungi

A number of fungi, microscopic organisms, cause diseases in turfgrasses. Though grasses are also prone to problems caused by poor cultural conditions or bacterial infections, fungi are the most common cause of disease in grass, according to the North Dakota State University Extension. Infection from a certain fungus causes purple discoloration on lawns.

  1. Disease Identification

    • Purple discoloration on grasses indicates helminthosporium leaf spot and melting out disease in lawn. All cool season and warm season grasses are prone to infection, with Bermuda grass and Kentucky bluegrass the most susceptible species. The causal fungus was previously classified as Helminsthosporium but is now identified as the Drechslera and Bipolaris fungi, namely Drechslera poae and Bipolaris sorokiniana, respectively.

    Symptoms

    • This fungal disease starts off with the appearance of small, 1/32- to 1/4-inch, purple-colored lesions on the grass blades. This early stage is referred as the leaf spot stage. As infection progresses, the spots enlarge and develop light brown centers. The margins of the lesion remain purple, and the centers remain tan in larger spots that often develop an hour glass shape. In advanced stages of infection, called melting out, the fungus enters the grass crown, and the grass starts to die from the tip down.

    Favorable Conditions

    • The leaf spot stage of the disease is exacerbated by extended periods of cold, rainy weather during April and May. The excessive use of nitrogen-rich fertilizers, during early spring, also causes disease progression. If not controlled in time, leaf spot moves into the more advanced stages during the warm summer, especially with high levels of precipitation. Lawns that are mowed very short are more prone to infection as grass gets stressed by low mowing heights. The spores of the causal fungi also gain an easier access to the roots and crown of the grass blades at shorter heights.

    Management

    • Symptoms of leaf spot may be reduced by irrigating the lawn during the early part of the day rather than late afternoon or early evening. Do not use high levels of nitrogen fertilizer between early spring and early summer. Reduce stress on the lawn by increasing mowing height, irrigating amply, reducing traffic on affected areas and de-thatching grass regularly. Chemical control options include the use of products with stobilurins, chlorothalonil or iprodione.

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Growing Jasmine
  1. Anthracnose Disease in Poa Grass
  2. Purple Grasses
  3. Diseased Grass
  4. A Cure for Lawn Rust Disease
  5. General Yellowing From Lawn Diseases
  6. Lawn & Grass Problems
  7. Fungi in My Grass Lawn
  8. Lawn Tips
  9. Mulching Grass
  10. Lawn Disease Treatment
  11. Round Spots of Dead Grass in My Lawn
  12. Dead Grass Spots in a Lawn

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