Weather conditions this summer have been perfect for the development of fungal diseases on lawns, such as brown patch. While there are things to know and do on the prevention end, September is time for the recovery steps.
Since brown patch does not kill the crown, which is the central growing point of the grass plant, turf affected by brown patch should recover in the coming weeks with some help.
From Purdue Extension’s brown patch publication: Brown patch can cause serious damage to tall fescue and perennial ryegrass residential lawns under certain conditions. The disease will result in thin, poor-quality turf as the fungus consumes leaves and tillers. Because brown patch does not affect crowns and roots, damaged turf areas should recover upon the return of weather favorable to turf growth, especially if turf is not further damaged by traffic and/or other stresses. Fungicides are available but should not be necessary for residential lawns. If a homeowner decides to pursue the chemical control option, then a professional lawn care service should be contracted for the application.
If your lawn has been damaged by this disease, your recovery steps will include some overseeding, followed by light fertilization in September and November. If the lawn has suffered from compaction, you may wish to have it aerified before overseeding. Some great tips on these steps can be found at extension.purdue.edu/extmedia/ay/ay-13-w.pdf.
How can you avoid this devastation in the future? The measures shown below are best practices that can help you to maintain a good-quality lawn that’s resilient against pests and diseases.
1. Limit nitrogen
Diseases such as brown patch are rarely found on unfertilized lawns, and there’s a reason for this! Nitrogen pushes out lush, tender growth that’s attractive to fungus diseases. Reduce nitrogen to the minimum needed to keep the grass green and you’re resisting the fungal onslaught. Make those applications mostly in the fall and you’re avoiding the one-two punch of lush, tender grass and the heat and humidity that favor those fungi About three pounds of actual nitrogen per thousand square feet is your baseline. You may need a pound more if you’re using irrigation.
So base your lawn care program on two fall applications, applying one pound nitrogen per thousand square feet in September and 1.0 to 1.25 pounds nitrogen per thousand square feet in early November. An additional application of one pound nitrogen per thousand in mid-to-late May will keep the lawn green and healthy throughout the summer. You can avoid the so-called “March green-up” fertilization completely, as it has more downsides than upsides.
People often don’t know how much nitrogen they are applying per thousand square feet, and that’s understandable. Sometimes, when I help a client figure it out, they discover that they are applying way more than three pounds per year. This makes the fungi very happy, and keeps the resident mowing constantly. Find out, and dial it back if it’s too much.
2. Water wisely
During most summers in the Midwest, lawns need watering to maintain color and density. Be aware, however, that extended periods of wetness favor those fungal diseases. If you water your lawn, try for early in the morning. Watering in the evening, together with dewfall, will keep the grass wet long enough for fungal diseases to get established. Watering during the daytime can be ineffective and wasteful due to evaporation and wind.
3. Mow high
All cool-season lawn grasses such as Kentucky bluegrass, perennial ryegrass and tall fescue in Indiana and Illinois perform best at a mowing height of 3 inches or more. High mowing gives the turf plants an advantage over weed germination by allowing them to shade and cool the soil. Alternatively, cutting short – “scalping” – exposes and heats up the soil, allowing weeds to germinate and overtake the grass plants.
4. Mow frequently
Mow as often as needed to never remove more than one-third of the leaf blade in a single mowing. In other words, if your mower is set at 3 inches, mow when the grass reaches 4 inches. This might be twice per week in the early spring and once every 2 to 3 weeks in the summer. Taking off more than one-third of leaf blades at a time can debilitate the grass and make it less able to recover from stresses.
5. Return the clippings
Bagging the clippings increases the time and effort needed for mowing. Leaving the clippings returns a slow, steady stream of nutrients and moisture, and does not harm the turf. Mulching mowers are effective for returning clippings, but older side-discharge mowers will also work acceptably.
I hope you can see that the easiest part of fungus prevention is basic lawn care, and not too much of it. For more on lawn care best practices, see extension.purdue.edu/extmedia/ay/ay-32-w.pdf.
Kris Medic is Bartholomew County’s Purdue Extension educator for agriculture, natural resources and community development. She also is a board-certified master arborist. She can be reached at firstname.lastname@example.org and 812-379-1665.