Brown & Yellow Streaks in Your Lawn May be Ascochyta Leaf Blight

Ascochyta leaf blight on iowa lawns

Do you see bleached tracks on your lawn that typically follow the path of your mower? It could be Ascochyta Leaf Blight, which is a grass fungus that is found primarily on Kentucky Bluegrass, the most common grass in Iowa. This disease causes irregular patches of straw-brown color and will make your grass appear dead. This can pop up overnight, having a great looking lawn one day and a streaky yellow lawn the next. Weather can have a factor in it as well, as it is typically preceded by wet weather that turns hot and dry. You will start seeing these damaged lawns near the beginning of June, but they can also occur anytime throughout the summer.

This is a foliar disease that kills the leaf tissue, not the root system. This also means that the disease is transferred by infectious spores that sit on the surface of the grass. The “dead” patches are commonly seen where your mower tires track because your tires will easily spread the spores as you mow your lawn. Given that the outbreaks are so random, you typically won’t notice your lawn is affected until after the patches are already there. Once they appear, there is little you can do to make them go away. The good news is that recovery should only take 3-4 weeks, depending on how the growing conditions are over that time. There also are some practices you can perform regularly to relieve stress on your lawn and lessen your chances of a yellow, patchy lawn appearing overnight.

The four main cultural practices you can do properly for a stress-free lawn are: fertilizingmowing, watering, and core-aerating. If you haven’t already, please consider our Weed and Feed fertilizing program. We apply the best products available in the correct amount at the right time. Mowing frequency, height of cutting, and blade sharpness are very important. Please be sure 2.5” – 3” of height remains after you’ve cut the lawn. Anything shorter than this causes stress on the lawn and allows weed infiltration. Never cut more than one third of the grass blade when mowing. And avoid mowing in the heat of the day, especially if the lawn appears to be wilting or starting to dry out. 

A healthy lawn needs 1” – 1.5” of moisture a week. It is best to water over night. Keep in mind, recovery will be slow and over-watering will not speed it up and may cause more problems. Keep up with fertility to promote re-growth. Core-aeration should be an annual practice especially for lawns that frequently have disease issues. Aeration reduces thatch levels and increases air movement, which allows the grass plants to dry more efficiently.

With this particular disease, curative fungicide treatments are not recommended. There are preventative fungicides available, but they must be applied before the problem appears. If we find a recurring problem, we may suggest preventative treatment(s) or over-seeding problem areas with varieties of grass resistant to the disease. We offer fertilization programs, aeration, and mowing services. Please contact our office if we can be of further assistance.

Does your lawn have summer patch disease?

Summer Patch Disease UltraLawn Cedar Rapids
Summer Patch Disease UltraLawn Cedar Rapids

Does your lawn look like this?

One of the most frequent diseases we encounter is summer patch. Summer patch is a soil-borne disease that attacks Kentucky bluegrass in the heat of the summer. The damage from summer patch presents itself as incomplete rings of discolored/dead turf, usually with a patch of live turf in the middle. This disease is sometimes referred to as “frog-eye” because of this appearance.

Certain conditions favor the development of this disease;

  • Lawns grown on compacted soil are much more likely to show signs of summer patch, as their root structure is stunted and is more adversely affected by the stress of heat and humidity.
  • Excessive thatch buildup also encourages summer patch development. Thatch prevents water from reaching the soil and acts as a sponge that holds moisture. Regular aeration, especially on sodded lawns, is highly recommended to both alleviate compaction and help remove excessive thatch.
  • Lawns that are watered lightly and frequently are more susceptible to disease. Diseases favor humid conditions, and a frequent irrigation schedule doesn’t allow the turf or thatch layer to dry out as it should. The rule of thumb when watering turf is “deep and infrequent”. The goal is to provide about ½” of water through irrigation, then not water again for 3-4 days or until the turf needs it.
  • Low mowing height puts undue stress on turf and makes it susceptible to all weeds, pests and diseases, not just summer patch. Mowing heights of at least 3” are recommended throughout the growing season. During times of extreme heat or drought, raising the mowing height to 3.5” is good practice.
  • Recent research has shown that summer patch tends to be more of an issue in soils that are lacking certain nutrients. There are 15 nutrients necessary for turf growth, and most of them are present in the soil. Different soil types are abundant or deficient in certain “micronutrients” (elements that aren’t needed in great supply), and soil tests will tell us exactly what is needed.

 

We typically see summer patch in sodded lawns that are 2-3 years old (although it certainly is an issue for golf courses and athletic fields too), and it is a condition that eventually goes away (research suggests 7-10 years). Over time, the soil builds up defenses and immunity to it, but it can be unsightly until then. Summer patch becomes active when soil temperatures reach 65 degrees, but it only shows itself during period of more extreme heat and humidity when lawns are under more stress.

Control of Summer Patch

Whenever we’re encountered with a pest or disease, there are two treatment options; chemical and cultural. Chemical control involves using pesticides or other compounds to eradicate an unwanted disease. Cultural practices involve a variety of management techniques meant to change the environment, so a pest won’t survive or find favorable conditions. We outlined a few earlier, but it would be useful to go over those again!

Cultural Controls for Summer Patch:

  • Aerate regularly to alleviate soil compaction and help prevent thatch build-up
  • Irrigate infrequently, and when you do irrigate, try for a deep watering of ½” water
  • Raise mowing height to at least 3”, and in times of extreme heat or drought, raise mowing height to 3.5”
  • Maintain consistent nitrogen fertilization throughout the season to avoid periods of time where the grass is starved for nutrition or excessively fertilized.
  • Maintain a soil pH around 6.5. This can be found with a simple soil test. Some “old wives tales” suggest adding lime to the soil every year to raise its pH. We rarely encounter soils with low pH in this part of the country, and a lime application is not likely to be needed.

Chemical Controls for Summer Patch:

Regular fungicide applications are effective on summer patch, but for the average home lawn, this method isn’t practical. These applications can be costly and must be done every 14-28 days. This program is typical of golf course putting greens or high-maintenance athletic fields.

As mentioned earlier, summer patch and other diseases tend to favor lawns that are deficient in certain micronutrients. At UltraLawn, we’ve helped customers with summer patch by making supplemental applications of micronutrients. This program is aimed at modifying the soil, which takes some time to accomplish. We’ve noticed that summer patch damage is less severe and recovers faster after one year of micronutrient applications. After two years, we can achieve near-complete control. These applications must go in conjuncture with the proper cultural practices outlined earlier.

As more university research is done on summer patch and information is gathered, we at UltraLawn will continue to pass our knowledge and expertise on to our customers. If you suspect that your lawn has summer patch or have any other questions or concerns, feel free to give our staff a call!