Reports of basal rot anthracnose on the rise

Summer turf diseases are in full swing. Tall fescue has brown patch, Kentucky bluegrass has dollar spot, perennial ryegrass has gray leaf spot, and creeping bentgrass/annual bluegrass has Pythium. Every year, Drs. Paul Vincelli and Gregg Munshaw from the University of Kentucky release “Chemical Control of Turfgrass Diseases.” This free publication is a must have reference for turf managers battling disease. It summarizes active ingredients, chemical families for resistance management, best management practices for fungicides, and specific recommendations for control of turf diseases. Click here to download a copy.

Basal rot anthracnose has been identified in southern and eastern Nebraska. While this disease is more commonly found on annual bluegrass, diagnosticians around the Midwest have been finding basal rot anthracnose on creeping bentgrass greens this summer. Symptoms on greens resemble patches of thinning turf (Fig. 1). Older leaves have a yellow- orange color and the stems can have a black and water-soaked appearance. Close inspection of the turf crowns with a hand lens will find that infected plants will have black spots (acervuli) with black hair- like mycelium (setae) emerging from the spot.

“Chemical Control of Turf Diseases 2015” has summarized basal rot anthracnose research and management recommendations from around the country. Here are only a few of the recommendations found in that publication for anyone managing basal rot this summer.

  • Heat, humidity and stress promote basal rot anthracnose. Reduce stress on greens with walk-behind mowers, raise cutting height and alternate rolling with mowing. Irrigate to 80% of ET daily and fertilize with low rates of soluble N every 7 to 14 days for best results.
  • Wet soils from compaction or high organic
    matter accumulation favor this disease when precipitation is plentiful. Use heavy topdressing and aerification to dilute and remove organic matter in the spring and fall.
  • Topdress in season with 1 cubic foot of sand every 1000 square feet each week to protect the growing point from damage during the season (traffic, mowing, etc.).
  • Vertical mowing has been shown to substantially increase basal rot damage.
  • Preventative application of fungicides are generally much more effective than curative control but should be started during late spring. Mixtures of DMI-class fungicides with chlorothalonil provide good preventative control of anthracnose. Penthiopyrad (Velista) has also provided good preventative control. Civitas has been shown to increase control when applied preventatively and season-long. Don’t use Civitas on turf that is already dying from the disease. • For curative control, mix systemic fungicides with chlorothalonil for best results. DMI and QoI (strobilurin) class products generally provide good curative control but will likely need to be re- applied every 14 to 21 days during the summer. Be careful to rotate chemical classes to reduce the risk of resistance that has been documented with the QoI fungicides.

From Bill Kreuser, Assistant Professor, Extension Turfgrass Specialist,