What is summer patch? Summer patch is a fungal disease that affects turfgrass root systems during the hot, humid days of summer. It is caused by the fungus Magnaporthe poae and can pose threat to sports fields’ playability, appearance, and health. Summer patch targets Kentucky bluegrass and fine fescues, two of the most common turf types used on sports fields. Warm-season grasses are not susceptible, and not all cool-season turf types are, either. Sports field managers should know that tall fescue and perennial ryegrass fields are not at risk.

How to Spot Summer Patch

For those sports field managers with Kentucky bluegrass fields, fine fescue fields, or both, detection is the first step to controlling summer patch. Sports field managers should be on the lookout for these symptoms:

  • Circular patches of wilted, yellow, or straw-colored grass
  • Patches that grow and range from around six inches to three feet in diameter
  • Affected areas where healthy grass is surrounded by diseased grass

When Summer Patch Begins and What it Does to Turf

Symptoms typically appear during periods of heat stress between June and September, but infection often begins when soil temperatures reach 65°F and higher at two inches of depth—long before it can be detected. At that time, the fungus will start damaging turfgrass plants’ roots, stolons, and rhizomes. When the infected turf’s surface appearance changes from a light color to a dark color, that indicates that root death has occured.

How to Treat Summer Patch: Cultural Methods

Proper cultural practices can significantly reduce the risk of summer patch. Here are a few to follow:

  • Syringing: Lightly misting the turf during the hottest part of the day can help cool down turf and reduce heat stress.
  • Irrigation: Water deeply but infrequently to encourage deep root growth. Deep roots can help turf withstand periods of drought and high temperatures.
  • Aeration: Aerate turf to improve soil drainage and reduce compaction. This allows for better air and water movement in the root zone.
  • Nitrogen Management: Ensure sufficient nitrogen levels in the soil. Balanced fertilization promotes healthy turf growth, making it more resistant to disease.

Chemical Control of Summer Patch

While cultural practices are always the first line of defense against turf diseases, summer patch doesn’t show its symptoms until it’s too late, so a preventative chemical approach will likely be necessary. Summer patch treatment usually involves four applications, spaced 28 days apart, that begin when soil temperatures reach 60°F at two inches of depth. Below, you’ll find an effective fungicide treatment plan along with example application dates put together by ATS rep Steve Lord:

  • Application 1 (May 1): Apply PPZ 143 and water it into the profile. Apply it once soil temperatures cross 60°F at two inches of depth for three days in a row. 
  • Application 2 (May 31st): 30 days later, apply Lexicon or Pillar SC and water it into the soil after application.
  • Application 3 (July 15th): 45 days later, apply Tartan Stressguard (no water required) for broad-spectrum future preventative.
  • Application 4 (August 10th): Apply Xzemplar for late season control and late summer dollar spot protection. Time this application 28 days after the third application.

Please note that this program is tailored to the northern regions of the United States, and programs will likely differ by region. There are many fungicide products to choose from, too. Fortunately, you and your ATS rep can build a tailored, effective summer patch control program just like the one above based on your region, budget, and preferences. As we mentioned, summer patch doesn’t show its symptoms until it’s already caused major root damage, so don’t be afraid to spray even if you haven’t observed any symptoms.

Integrating Cultural and Chemical Approaches

For the most effective control possible, use both cultural and chemical control methods. Keeping turf hydrated, aerated, and ensuring proper pH (6.0-6.5) and nitrogen levels will ensure turf is ready to battle all types of summer-related stressors—not just summer patch—including traffic from athletes. Fungicides will go a step further and keep summer patch and other diseases from popping up, killing your turf, and negatively impacting playability.

Remember: Prevention is Key

Recognizing that summer patch treatment is a preventative game is important, so be sure to develop a treatment plan and start applications right away when conditions are right. Your ATS rep can help you get out ahead of symptoms with a treatment plan and/or give recommendations. Reach out to them for more information on summer patch and how to prevent it to protect your sports turf’s health and playability. If you’re new to ATS, you can use our rep finder tool to find one near you.