Bermudagrass Leaf Spot

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Submitted by:  Eve H. Honeycutt Extension Livestock Agent

Lenoir and Greene Counties

Bermudagrass leaf spot is caused by a fungus from the genus Helminthosporium and the disease has been informally called Helminthosporium leaf spot, Helminthosporium leaf blotch, or Leaf Blight.

Leaf spot is a fungal disease that is brought on by constant wet conditions, especially when the forage is tall and cannot dry thoroughly between rain storms.  We saw a lot of leaf spot last year because of the same weather pattern in late summer.  On the grass itself, leaf spots are more numerous near the collar of the leaf blade. Leaf lesions are irregularly shaped and brownish green to black in color. Infected plants may occur in irregular patches. Extensive damage occurs when the pathogen attacks crowns, stolons and rhizomes. Severely affected hayfields may become brown and thin.
The good news is that leaf spot will not hurt your animals, though it does make the grass less tasty.  The bad news is there is very little you can do about it.  There are no fungicides approved for forage crops.  The best thing you can do is manage your stand of bermudagrass as best as you can.  Leaf spot will reduce yields and will continue to spread as long as the conditions remain moist.  One of the best preventative measures is to make sure your soil has adequate potassium levels (as shown on your soil sample analysis).  Potassium allows the soil and the plant to be healthy enough to fight fungal diseases like leaf spot.  Potassium is supplied in the form of potash, and the soil typically needs 75% as much potash as nitrogen EACH season to maintain adequate fertility and disease resistance. 

Keep an eye on your fields through this rainy weather and watch for irregular discoloration or thin yields.  If you do get leaf spot in a field, the frost this winter should kill it and it should come back next year.  Be sure to monitor your soil sample and follow the recommendations for all the nutrients, not just nitrogen.