Fungus can be both a good and a bad thing. Mushrooms on pizza are an example of good fungus. Fungus in lawns, on the other hand, are nearer the other end of the spectrum. If your turf is looking a little thin and brown in spots; you are not alone. Fungus and hot temperatures have wreaked havoc on lawns this year, but there is still time to make your lawn look full and lush for this fall.
Dollar spot is a fungal disease that is common in lawns. This fungus doesn’t discriminate in the type of turf that it infects, but it is most common in Kentucky bluegrass. The symptoms will be 4-6 inch straw colored patches in the lawn. The grass blade itself will have a bleached lesion, or spot, with a reddish-brown margin that extends across the grass blade.
There are several practices you can use to deal with dollar spot. Some of the recommended cultural practices include irrigating in the early morning to remove the dew from the turf and irrigate enough to maintain plant vigor and avoiding drought stress, but not so much that it is over irrigated. Also try to limit the amount of traffic that goes across the turf in the early morning. Cultural practices can be used to reduce the potential for dollar spot in turf, but in some cases a fungicide treatment may be needed for control. If fungicides are used, treat the lawn as needed at the first sign of the infection. There are several products on the market labeled for the treatment of dollar spot, read and follow the label instructions for application amounts and reapplication intervals.
Heavy infestations of fungi like summer patch and brown patch are being seen in cool season turf like Kentucky bluegrass and tall fescue. The disease cycle of these fungi started in the turf long before the symptoms are visible. These diseases don’t cause any leaf spots on the leaf blades, but rather the infected plants may have dark brown to black roots. The roots of the plants were infected by the fungi in early spring to early summer. When the hot summer temperatures hit, the roots were not able to take up moisture needed to support the rest of the plant. The symptoms start out as yellow-tan arcs, rings, or ‘frogeyes’ in the affected turf. As the season progresses, the yellow turf turns dormant or brown. The symptoms are often seen in areas of full sun or in areas that are high stress, like near sidewalks and driveways. The dead turf will have dark brown to black roots and will secure in the ground, unlike with grubs where the turf will roll up or lift up like a carpet.
Some of the recommended cultural practices can decrease the instance or severity of the infection. The grass should be irrigated to maintain plant vigor and avoid drought stress, but not so much that it is over irrigated. Maintaining a good fertility program, avoiding over fertilizing, and keeping your mowing height tall, 3-3.5 inches, throughout the entire season will also help decrease the severity.
What can you do right now to cure patch diseases in the lawn? Sad to say, there is no curative treatment for your lawn now for those fungal infections. If you have a lawn with a history of fungal infections, a preventative fungicide application can be effective, but control of the problem can be patchy. If you choose to apply a fungicide to control summer patch, applications should be made after the 2 inch soil temperatures reach 65 degrees F in mid-afternoon for 5 consecutive days and repeated a month later. Applications should be done by professionals for best control. Focus the applications in the areas that have had problems in the past.
If your lawn does start looking a little rough due to fungus or hot temperatures, there is still time to fix it this year. Overseeding or reseeding with a good quality seed will make your lawn full and lush before winter hits and get you off to a good start next spring. September 1st through September 15th is the perfect time to reseed or overseed those bare spots in your yard with resistant turfgrass cultivars. When overseeding a thin stand of Kentucky bluegrass, apply improved cultivars at .75 to 1 pound of seed per 1,000 square foot. If you are overseeding a tall fescue lawn, use a blend of improved turf-type tall fescue cultivars. Apply 4 to 6 pounds of seed per 1,000 square feet. Be sure that the seed has good seed to soil contact and water it in order to get the best germination out of the seed.
Keeping an eye out for the fungus among us is always a good idea to know the progression of the infection, the timing of the occurrence, and an opportunity to change our cultural practices to help prevent further problems.
Elizabeth Killinger is the Horticulture Extension Educator with Nebraska Extension in Hall County. For more information contact Elizabeth at firstname.lastname@example.org, her blog at https://huskerhort.com/, or HuskerHort on Facebook and Twitter.