Turf Disease - Joseph W. Rimelpsach Todd E. Hicks Amy Stone


Remember the majority of turfgrass problems are not caused by diseases but are the result of two key factors.

#1. Adverse weather conditions that are not conducive for growing cool-season grasses. 

#2. Injury or damage to the turfgrass plants from use and ware and/or maintenance procedure that were not properly executed.

Here the focus will be on some of the common infectious diseases that can occur in Ohio and the Midwest in spring. These are caused by fungi and often weather conditions are the driving factor for development and degree of severity. Keep in mind that the different grasses that make up a lawn, sport field, golf course, park, etc. will vary in their susceptibility to different diseases. 

Snow Molds:

Coming out of a wet mild winter, it is a good bet we are going to have some pink snow mold issues. Raking affected areas and make sure there is adequate fertilizer to heal damaged turfgrass. This disease is primarily on creeping bentgrass on golf course. 

Snow MoldPink snow mold, occurs without snow and is often referred to as Microdochium patch or Fusarium Patch, caused by the fungusMicrodochium nivale.Here the disease is in creeping bentgrass. In spring the disease appears similarly on other grasses. (Photo by J. W. Rimelspach)

Snow MoldEarly spring pink snow mold in a perennial ryegrass baseball infield. The ryegrass was planted the previous fall and went into winter in a juvenile, lush, highly susceptible state. (Photo by J. W. Rimelspach)

Snow MoldPink snow mold in perennial ryegrass under wet conditions. Note the slimy collapsed leaf tissue, in this case the crowns are still alive and have the potential to recover. As the turf and site dry out the affected patch will become a crusty mat of dead leaf tissue. Check the condition of the crowns to see if alive. (Photo by J. W. Rimelspach)

Red Thread:

Cool, mild temperatures, humid, overcast periods typical to Ohio’s wet springs provide the best environment for disease development. Prolonged leaf wetness and slow turfgrass growth also contribute to disease development and severity. Red thread is most severe under low Nitrogen and / or low Phosphorous levels. In Ohio, Red thread has been recorded as being active in every month of the year but in most year’s spring and early summer or the fall is when the disease is most active. 

Management and Control Strategy –

- In general, any practice that encourages optimal growth of turf should be employed such as maintenance of a balanced fertility program, good drainage, good light, etc. Increased N and P fertility has been correlated to decreased red thread susceptibility. 

- Adequate phosphorous is critical to minimize and manage red thread. Soil test to know what available phosphorous levels are and correct if needed.

- Varieties with different levels of red thread susceptibility are listed at the National Turfgrass Evaluation Program web site:www.ntep.org

Over view of lawn with red threadOver-all view of symptoms of red thread in Kentucky bluegrass and perennial ryegrass turfgrass. (Photo by J. W. Rimelspach)

Patches of turf affected by red threadAffected “spot” with red thread in a lawn of bluegrass and ryegrass. (Photo by J. W. Rimelspach)

Close up of red thread fungus on leavesClose up of the red thread fungus growing out of the end of a perennial ryegrass leaf. The color of the fungus can vary from a red to pink or coral color. As the fungus ages and dries out the color will be dull pink or more tan. (Photo by J. W. Rimelspach)

Leaf spots:

Another early spring problem that occurs is leaf spot. During the last several years it has been an ever increasing problem. The reason leaf spot is such a recurring problem is that there are so many types of leaf spot pathogens. They span the temperature range from warm to cold but have one thing in common, excesses water. Long periods of wet leaves is ideal for the disease. Spring showers bring more than May flowers! 

Management and Control Strategy –

To manage consider the following.Raise cutting height, mow frequently to avoid stressing turf, avoid excessive nitrogen but provide adequate complete fertilization, avoid frequent watering and wet turf and select more resistant cultivars to the disease.

Leaf spot, close up on leavesCommon leaf spot(Drechsler &/orBipolaris spp.)infecting Kentucky bluegrass