Brown lawns sprouting up in area

Lawns have not been looking so good these past few weeks. With all the rainfall, one might think they would be lush and green instead of weak and yellow or brown and spotty. However, too much rain, or too wet of a soil, can be just as harmful as too little moisture.

Other than turning off the irrigation system when the soil is wet, there's not much else to be done at this time of the year. Correct fall lawn care practices will help most lawns recover. Consider core aerating your lawn and overseeding with disease resistant grass cultivars in September.

Much of the browning in lawns is due to fungal disease. I've seen quite a lot of brown patch (Rhizoctonia solani) and dollar spot (Lanzia and Moellerodiscus species). Like many fungal diseases, these are promoted by wet weather, which allows fungal spore to more easily infect turfgrass over a longer period of time.

Brown Patch causes roughly circular patches or rings of brown grass. Dollar Spot causes smaller, 3-6 inch diameter, circular patches of brown grass. With both diseases, the brown areas often coalesce into one large brown area and the rings or circles become less noticeable.

On close inspection of green grass blades near infected areas, leaf lesions or spots can be found. Brown patch causes small gray to tan colored spots with red margins that often cover only half of the leaf blade. Dollar spot causes light tan lesions with red margins on the top and bottom. Dollar spot lesions completely encircle a grass blade.

In many cases, lawns damaged by brown patch and dollar spot recover in a few weeks, unless the outbreak is sustained by continuous hot, humid or wet weather. Our continued rainfall has sustained the diseases and we are seeing more than we would in a normal year.

However, fungicide treatments after mid-August are not very effective; and fungicides applied now will not eliminate the fungus from your yard so you won't have to deal with it next year. Most fungicides protect the grass blade and prevent it from being infected, rather than actually killing fungi present in the lawn.

It's better to use good fall lawn care practices of fall fertilization, correct mowing and irrigation and core aeration to encourage turf recovery. Because the fungal spore count is being increased this year, watch your lawn next year. Fungicides applied at the first sign of disease, often in late June or July, can reduce but probably not eliminate fungal disease.

Browning in lawns can be caused by a number of factors. It's a good idea to inspect lawns closely to determine the actual cause of symptoms. If you cannot find any lesions on grass blades, cut and roll the sod back to check for white grubs. If you can find eight grubs per square foot, consider an application of Dursban insecticide.

If you cannot find white grubs, look closely at turfgrass roots. If they appear soft and brown instead of crisp and white, you may have a root disease called summer patch (frog-eye). In this case, lawn patches will appear straw colored and matted. If summer patch is the cause, it's important to begin an overseeding program of resistant cultivars. If fungicides are applied for this disease, they are effective if applied in late April or early May to protect roots during the infection period.

Contact Kelly Feehan, Extension Educator, at 563-4901 or e-mail her at kfeehan2@unl.edu.