How to Spot and Prepare for Turfgrass Root Diseases on Golf Courses
As temperatures rise and summer arrives, root diseases begin to emerge. We’ll explore the symptoms and causes of different major root diseases, several other diseases, the soil temperature range and depth to treat at, and effective control methods.
Fairy Ring
Fairy ring is a turfgrass disease caused by fungi of the Basidiomycota division of fungi that form in a circle or “ring”. A species commonly referenced is Marasmius oreades, but there are over 50 different fungi that can cause the disease. The exact type of fungi doesn’t really matter, though—at least for our purposes. What matters is recognizing it and getting rid of it.
Fairy ring symptoms vary and can be identified visually as:
- A ring of grass that is higher and darker than other turf,
- A ring of dead, brown grass,
- A ring of mushrooms,
- Or a combination thereof.
Turf that is closely mowed and/or has a nitrogen deficit is especially susceptible, so greens are going to be the prime target for this disease. While fairy ring won’t kill your turf, it does present major aesthetic and playability issues. It’s crucial to identify these symptoms early on and use fungicides designed for fairy ring—especially those containing demethylation inhibitors (DMI fungicides)—that suppress fungal activity and promote turf recovery. Apply when the soil temperature is around 55 to 60°F for preventative control.
Product Options: Densicor, Fame SC, and Kalida are all effective fungicide options for fairy ring control.
Temperature Range: 55-60°F
Depth: 2 inches
Pythium Root Rot
Pythium root rot (PRR) is a disease caused by water mold pathogens of the Oomecyte order, and it attacks the roots of turfgrass, causing rotting and decay. It can affect a wide range of turfgrass species, primarily cool-season turf types.
Infected roots will appear brown, be water-soaked, and exhibit a foul odor. Above-ground symptoms include streaks of yellowing, thinning, and dead patches.
PRR thrives when it is hot and wet, but even areas with proper drainage can be affected—saturation is the only requirement for it to appear. Slow growth due to extreme temperatures can kick the disease’s progression into overdrive, too.
Recognizing the signs early on is crucial for implementing an effective pythium root rot treatment plan. When combating pythium root rot, choosing the right fungicide is paramount. Fungicides specifically designed for Pythium control should be applied preventively.
Product Options: Proplant, Segway, and Serata are fungicides that are specifically designed to control pythium root rot.
Temperature Range: 60°F+ (heat stress will exacerbate symptoms)
Depth: 2 inches
Take-All Patch
Take-all patch is a root disease caused by the Gaeumannomyces graminis fungus that predominantly affects bentgrasses between the spring and fall seasons. The disease can be identified through large patches of discolored dead and/or thin grass, typically circular in shape. Rings can also appear. Heat stress and dry conditions can create large patches of various sizes and colors, ranging from the standard brown and yellow to a grayish blue.
Take-all patch loves to target sand-based areas like greens, which are especially susceptible. The disease takes effect in the fall and spring, and effective treatment involves a combination of cultural practices and fungicide applications. The usage of ammonium and manganese sulfate can decrease its severity.
Selecting the best fungicide for take-all patch is crucial, and often, DMI fungicides are recommended for their efficacy against the causal fungus. Additionally, maintaining proper soil pH (lower than a pH of 6.5) and promoting good drainage can significantly contribute to preventing take-all patch. Preventative fungicide treatments should take place during the fall when soil temperatures are below 60°F but above 45°F. Treating preventatively is the only viable chemical option, as the efficacy of curative treatments is minimal.
Product Options: Fungicides that control take-all patch include Tourney EZ, Patch Amino 5, and Pillar G.
Temperature Range: 55-60°F
Depth: 2 inches
Summer Patch
As the name suggests, summer patch is a root disease that tends to rear its head during the hot summer months. The Magnaporthe poae fungus is responsible for this heat-induced disease, which targets the roots and crown of turfgrass, leading to characteristic patches and rings of wilted and necrotic grass.
These patches and rings grow in size as the disease spreads, ranging from 1-3 inches in diameter at inception, to up to three feet when the disease has fully taken hold. Under the surface, the root and crown will be discolored and appear brownish-red or brown.
Treating summer patch involves a combination of cultural practices, such as proper irrigation and aeration, alongside targeted fungicide applications. Effective summer patch fungus treatment isn’t complete without preventative fungicide applications. Systemic DMIs and Quinone inhibitors will be most effective when applied when soil temperatures are in the mid to upper 60s.
Product Options: Fungicides like PPZ 143 MC, Tourney EZ, and Patch Amino 5 provide control over summer patch.
Soil Temperature Range: 65-70°F
Depth: 2 inches
Additional Diseases
Root-specific diseases are important to prevent and treat, and so are dollar spot and anthracnose, which are not root diseases but affect turfgrass negatively all the same.
Dollar Spot
Caused by the Clarireedia fungal genus (formerly classified as Sclerotinia homoeocarpa), dollar spot can cause small, circular brown or bleached patches on greens. The disease got its name due to the size of the affected areas being similar to that of a U.S. silver dollar, which measures in at about 1.5 inches in diameter. Dollar spots are typically between one to three inches in diameter. They will appear near each other, since wind, water, and traffic spread the disease. In addition to the discolored patches, mycelium can appear in wet, dewy conditions.
Dollar spot typically appears during late spring and into late fall when air temperatures range from 60-90°F. Depending on latitude, that range may cover the entire timeframe. Dollar spot control doesn’t have to be difficult, though. Moisture management techniques and the application of varied preventative fungicides can help keep dollar spot off turfgrass while combating resistance. If control efficacy appears to have decreased, consider using another fungicide with different ingredients.
Product Options: Fungicides like Zoxy-T, PPZ 143 MC, and Lexicon are effective options for controlling dollar spot.
Air Temperature: 60-90°F
Anthracnose
While detecting fairy ring doesn’t involve much detective work, anthracnose can be difficult to spot and diagnose. Anthracnose is a disease caused by a group of fungi (Colletotrichum cereale) that attack the crown and roots of turfgrass—particularly putting on greens—during periods of stress (both cold and hot) resulting in basal rot.
You can identify anthracnose by observing turf for thinning and discolored (brown/tan in appearance) grass. There is no pattern to where these discolored spots will appear. An easy way to tell that you may be looking at a patch of anthracnose-affected turf is by determining if it gives off the appearance of camouflage. Much like a camouflage pattern, the area will be splotchy with random areas of green and brown.
Treating anthracnose is a largely preventative game. Proper agronomic practices will give superintendents an edge on the disease, but DMI fungicides will play a vital role in keeping the fungus and guarding the turf from stress. Fungicides will be most effective when applied when soil temperatures are around 65°F. Curative control is possible with DMIs, but an ounce of prevention, or whatever amount your product’s label says to use, is going to be the best way to combat anthracnose.
Product Options: Armortech CL720, Maxtima, and Honor fungicides are all viable options for controlling anthracnose.
Temperature Range: 65-70°F
Depth: 2 inches
Treating Root Diseases
Throughout our exploration of turfgrass root diseases, one recurring theme has been the efficacy of demethylation inhibitors (DMIs) in fungicides. But what exactly is a DMI fungicide, and why does it play a significant role in disease management?
DMIs target the demethylation process in fungi, which disrupts their ability to produce essential sterols for cell membrane formation. This mode of action makes DMIs effective against a wide range of fungal diseases, including those affecting turfgrass roots. However, it’s crucial to be aware of DMI fungicide resistance, as over-reliance on a single class of fungicides can lead to decreased effectiveness over time.
In addition to cultural practices such as proper irrigation, aeration, and soil management, fungicides are vital for managing the wide spectrum of root diseases. If you’re looking for advice, products, or anything else, we’re here to be a resource. Drop one of our folks a line, and they’ll reach out!
