Anthracnose Basal Rotby Geoff Simril

Blog, Golf, Turf & Landscape March 13, 2012 9:19 am

Photo source http://www.turfgrass.ncsu.edu

Anthracnose basal rot is a very destructive crown rotting disease that affects creeping bentgrass and annual bluegrass (poa annua) on putting greens. In the Midwest, the disease has been observed more often on creeping bentgrass than on annual bluegrass, but in the East, it affects primarily poa annua.

Disease development is most often associated with abiotic factors such as high temperature and humidity, drought stress, excessive soil moisture, low mowing heights, soil compaction, shade, poor air circulation, and/or inadequate nutrition, all of which stress the turfgrass.  In other words, anthracnose is a stress-related disease.  Dr. Bruce Clarke of Rutgers University has observed that he cannot innoculate healthy turf with anthracnose.

Anthracnose basal rot is one of the more difficult diseases to control, especially after symptoms appear. The disease was hardly discussed over 10 years ago, but it has seemed, at times, to reach epidemic status as Superintendents have been pressured to provide faster and faster putting speeds.  The combination of very low mowing heights and “lean and mean” nutrition programs put turfgrass, especially poa annua, under severe stress.  With the increased summer temperatures and high humidity prevalent in the last 6 years, it’s not surprising that the incidence of anthracnose has increased significantly.

There’s not much a Superintendent can do about the weather.  So, the best strategies against anthracnose deal with all of the controllable factors that contribute to turfgrass stress and disease development.  You have to do everything you can to keep turfgrass healthy.  That means following a proven fungicide rotational program, improving air circulation and water management/distribution, and increasing root growth and carbohydrate reserves with biostimulants like seaplant extract and humic and fulvic acids.  It also means increasing the amount of Nitrogen.   Research conducted by Dr. Clarke with Harrell’s MaxLine products has demonstrated that the most effective nutrition programs comprise quality foliar inputs of .2 lbs of N per 1,000 sf every 14 days (or 1/10th of a lb every 7 days).  Foliar applications in the summer should be supplemented with granular applications in the fall and spring.  Dr. Clarke recommends increasing N in the spring to 1 pound per 1,000 sf.

Other measures supported by Dr. Clarke’s research include:

• Suppress seed heads to retain reserves in the plant
• Increase potassium, and use a potassium phosphite like Title Phyte to increase the plant’s defenses
• Firm the surface through increased topdressing with angular sand and by rolling more frequently
• Tank mix different chemistries because there are multiple strains of anthracnose

Finally, Superintendents should do all they can to raise the mowing height.  Putting speeds can still be maintained with proper growth regulation and with rolling.   Primo MAXX® (trinexapac-ethyl) is an especially beneficial growth regulation chemistry for poa annua; it helps increase root growth and carbohydrate reserves.  Research at Oregon State University has demonstrated that putting speeds can be increased over mowing every day by a combination of rolling and mowing.  Light, frequent topdressing can also help, by minimizing thatch development and by effectively raising the height of cut.

It is possible to give the players what they want and the turfgrass plant what it needs to fight off anthracnose infection.

Primo MAXX® is a registered trademark of Syngenta Group Company.

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