Fungicides, Red Thread, Leaf Spots, Patch Diseases and Dollar Spot

July 7, 2015

2010 Fungicide Recommendations for Turfgrass:

Fungicide recommendations for 2010 for turfgrass are now available. This year’s revisions on turfgrass fungicide recommendations can be found under the publications section for the latest version of “Management of Turfgrass Diseases” Bulletin L-187. Please be advised that the copy available on Ohioline is an old version and some recommendations are not complete.


Red Thread:

This relatively superficial disease has become active in many parts of the state, especially on ryegrass and fine fescue. Red thread can be found on all cool season grasses depending on the situation. However, it is most common on perennial rye, fine fescue, and to some degree on Kentucky bluegrass. The disease can be identified form the pinkish to reddish colored patches. The color and texture can vary considerably. Often, the patches will appear to give a pink color to the leaf blades or to resemble pinkish globs of bubble gum or cotton candy on the leaf blades.

This disease is strictly a superficial problem and one that will not kill the turf. Under serious conditions, it can reduce the overall appearance of a lawn. Make sure the lawn has adequate nitrogen and phosphorus to manage a healthy robust stand of turf. A deficiency of either significantly increases disease severity. Fungicide programs can be considered in unusual situations where the disease needs to be prevented. Look under publications for the “Management of Turfgrass Diseases Bulletin” for the latest fungicide recommendations for 2010.

bygl 1 5-20-10: Over all symptoms of red thread on perennial ryegrass.
Overall symptoms of red thread on perennial ryegrass.

bygl 2 5-20-10

Red thread on lawn: Note the pinkish fungus on leaf blades.

Leaf Spot - Melting Out:

Several weeks ago, leaf spot was reported to be active. On lawns that are susceptible to the disease, there may be extensive thinning of the turf. This problem is primarily on common Kentucky bluegrass lawn areas and can be quite decimating to the turf. The leaf spotting stage will continue with cool, wet weather conditions. With the advancement of warmer and dryer conditions, the disease progresses down the stem tissue and into the crown which can cause the turf to thin.

To manage the disease, properly mow the turf high to allow long leaf tissue for maximum photosynthesis and food production for the plant and to prevent stressing the turf from scalping. A sound fertility program is also beneficial to maintain the plants during this disease period but avoid high rates of nitrogen which will increase severity. Application of a fungicide would not produce quick results since the disease has become firmly entrenched in the turf plants. Fungicides may help in recovery; however, progress will be slow. Often the expense of the program is not warranted. Specific fungicide recommendations can be found on the “Management of Turfgrass Diseases Bulletin” for 2010.

Patch Disease Alert:

If you are managing lawns that have had a history of necrotic ring spot or summer patch now is the time to consider the first application of a preventative fungicide program. There are various rules of thumb. However, once the soil temperatures reach approximately 60°F or slightly warmer at a 3 inch depth for several days in a row, research indicates that this is an ideal time to apply the first fungicide application. These materials must be applied with high volumes of water so that they will be drenched into the crown and upper root system to be the most effective. Since the disease is a crown and root disorder, the fungicides must reach this part of the plant to be highly effective. If there are questions about this, refer to our summer patch fact sheet for more information. Specific fungicide recommendations can be found on the Management of Turfgrass Diseases Bulletin”.


The follow diseases and disorders are active and have been reported or identified on samples to the C. W. Ellett OSU Plant and Pest Diagnostic Clinic.

- Dollar Spot on fairways and tees.

- Red Thread mainly on perennial ryegrass and fine fescue may be seen on bentgrass.

- Microdochium Patch (Pink snow mold) this week has been PERFECT weather conditions for this disease. At this time of year the disease is primarily on annual bluegrass (Poa annua). The spores are easily move in water, symptoms may follow water runoff patterns, and tracked by mowers.

bygl 3 5-20-10

Microdochium Patch (Pink Snow Mold) in Poa annua green, moved by mower.

bygl 4 5-20-10

Microdochium Patch (Pink Snow Mold) on Poa annua green.

- Leaf Spot on creeping bentgrass greens has occurred at 3 different golf courses. The annual bluegrass is usually normal and only the bentgrass affected which seems to slowly thin and turn a dark brown rust color.

bygl 5 5-20-10

Leaf Spot of green of creeping bentgrass 'L-93', Columbus, Ohio

bygl 6 5-20-10

Leaf Spot on a fairway of creeping bentgrass 'L-93', Columbus, Ohio

- Foliar/leaf Damage on Greens from mower damage and /or aggressive sand top dressing and dragging into the canopy. Check the quality of cut and leaf conditions by carefully examining the greens with a hand lens.

bygl 7 5-20-10
Poor mowing on bentgrass. Note shredded ends on leaves.