Many lawns, especially bermudagrass and zoysia lawns, are being hammered with leaf blight diseases since the daily rain showers have begun. I tend to group several of these leaf blight pathogens into the Helminthosporium melting out complex. Our turf pathologist may be more specific with terms such as Bipolaris spp., Curvularia spp., or Exserohilum rostratum. These pathogens are favored by leaf wetness and stressed turf so any cultural practices that can reduce either will be helpful. Maintain adequate soil moisture but avoid late afternoon irrigation that keeps the foliage wet overnight. Reduce thatch layers that tend to hold moisture in the turf canopy. Be judicious with fertilization especially nitrogen during extended rainy periods. Scout for any symptoms of leaf lesions and thinning, “melting out”, of the turf and be prepared to apply fungicides if necessary. Fungicides such as azoxystrobin, fludioxonil, pyraclostrobin and others are effective against these pathogens. The Mississippi State University disease diagnostic lab for a minimum fee will identify from samples submitted from your lawn any turf pathogens and recommend procedures for management of these diseases. This lab is located in the Bost Extension Building on campus and can be contacted by calling 662-325-2146.
Dr. Wayne Wells is an Extension Professor and Turfgrass Specialist. His mailing address is Department of Plant and Soil Sciences, Mail Stop 9555, Mississippi State, MS 39762. email@example.com