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Summer Turf Diseases on Home Lawns

This past summer has been an exceptional year for diseases on turfgrass, and home lawns weren’t immune to these diseases either. Dr. Christian’s has mentioned several times this summer that this summer was the worst Brown Patch in Iowa he has seen in 30+ years. Summer temperatures often in the 80’s and lows in the upper 60’s with high humidity and rainfall made the conditions perfect for these summer diseases. The good news is that the temperatures seem to have cooled and repairs can be made to yards.

With the warm temperatures, ample rainfall, and high humidity this past summer, Iowa lawn’s endured prolonged periods of perfect weather conditions for brown patch (Rhizoctonia solani). This disease was noticed in Iowa from June on into September. It is often noticed as circular patches from a few inches to several feet.

Brown patch at the ISU Horticulture Research Station
Brown patch on creeping bentgrass putting greens at the Iowa State Horticulture Research Station.

The area in the patch can become killed and create a sunken patch, often though this disease will not completely kill the turf, but rather just thin those spots, which can recover with proper care after the weather conditions change. Brown patch lesions on leaves are easy to identify and are irregular tan or light brown in color with the edges of the lesions being a dark brown in color.

A close picture of brown patch lesions on turfgrass leaves.

Another problematic disease this summer was summer patch (Magnaporthe poae) which happens predominantly on Kentucky bluegrass and commonly occurs when temperatures are above 82. It is caused by a fungus that colonizes the roots. These patches often appear suddenly as small yellow patches, since the roots are affected, adding water will not help the declining turf health. As the grass dies it will turn a straw color. These patches often have areas inside of the patch that are not affected and seem healthy. Symptoms of summer patch will not be noticeable when the weather cools. Promoting healthy roots will help to minimize the impact of summer patch by regular aeration in the fall, mowing at proper mowing heights, and improving drainage in the yard.

Disease on turfgrass lawn

If these diseases injured your turfgrass the fall is a great time to recover from them, as healthy turfgrass is the best way to combat weeds and disease next year. Make sure your yard is fertilized this fall, aeration each fall to improve gas exchanges to the roots and improve drainage making them healthier can help, follow proper mowing heights for the turfgrass species that are present in the yard, and overseed with more grass seed if large areas of dead turf exist.

Aerators can help improve drainage and promote healthy turf.

One final note, several calls and emails this week have been related to people mistaking disease damage for chemical damage. Remember that typically disease damage will be patchy, while chemical damage would be a complete grass kill or in straight lines.

Below are a couple pictures of disease damage on lawns from the Ames area:

Summer disease damage to a lawn in Ames

Turfgrass diseases can become a large problem is conditions exist for a long time.

For more information on how to renovate a yard visit: https://www.extension.iastate.edu/turfgrass/search/content?f[0]=im_field_...

Category:

iaTURF Blog

Tags:

summer patch, brown patch, turfgrass, disease

GRAY LEAF SPOT ON LAWNS

Now that the snow is mostly gone, we are seeing some common early spring problems in lawns. Here are a couple of things that I observed in my own lawn yesterday.

The first is Gray Snow Mold, caused by fungal organism (Typhula incarnata). This is a common problems that develops in lawns at this time of year.

Here is how I know what it is. The brown fruiting bodies on the tissue are "sclerotia", which are commonly associated with this disease on turf.

The second problem is a feeding trail of voles that were active under the snow.

Feeding Trails

Here is the culprit (Picture from Timothy Christians)

There will likely be several turf problems showing up in the next few weeks. I would appreciate any picture that you have for the blog.

Category:

iaTURF Blog

Tags:

Gray Snow Mold, fungi, disease

SLIME MOLD SHOWING UP ON TURF

The wet weather has resulted in an increase in slime mold showing up on lawns. This problem is caused by primitive fungi that exist primarily as saprophytes (organisms that live on dead organic material) and use living grass plants for support. Fungi in the genera Muctlaga and Physarium are usually the causal agents. They can take on a wide variety forms. Sometimes people describe it as something that looks like the dog threw up on the lawn. Other times it looks like gray slime on the leaves. Then, it can take on some truly strange appearances that you would not associate with a fungi.

The fungi can be washed off with a hose. It will usually go away after the wet dreary weather changes. We generally do not recommend fungicides for this problem.

Larry Ginger of American Lawn Care sent in the first picture earlier this week. This is typical of the way slime molds generally appear in wet weather.

Slime Mold

Here is a close up of some slime mold from the research station.

Here is one from my own lawn that looks like the dog threw up.

Here is the most unusual one that I have seen. This came from a lawn in Iowa.

Category:

iaTURF Blog

Tags:

disease, slime mold, fungi

RUST DISEASE ON PERENNIAL RYEGRASS

On July 17, I received an e-mail from Larry Ginger of American Lawn Care with a picture of rust disease showing up on perennial ryegrass, but not on Kentucky bluegrass. Rust is a fungal disease caused by fungi in the genus Puccinea.

Picture from Larry Ginger showing rust on ryegrass patch in lawn taken July 17.

I had not seen this problem at that time, but yesterday (July 21) I took data on the National Turfgrass Evaluation Program (NTEP) trial at the research station. I found that many of the cultivars were covered with rust. I took data on the rust problem this morning (July 22). I have not seen the problem on the Kentucky bluegrasses as of today, but it clearly a severe outbreak on some of the perennial ryegrasses. Rust often shows up in August on Kentucky bluegrass, perennial ryegrass, and even on tall fesuce (see earlier blogs). This year it is early and appears to be hitting the ryegrasses first.

Close up of rust on Kentucky bluegrass from last year.

Rust spores on my shoes after taking data.

Three pictures of individual ryegrass plots covered with rust on July 22.

Rust is clearly cultivar specific and there were cultivars covered with it and adjacent plots that were completely free of the disease. This is another reason for choosing your grass seed carefully. There is usually a good reason to spend a little more on grass seed. I have not analyzed the data on which cultivars were affected, but that will be in next year's report. NTEP does have data available on ryegrass susceptibility to this disease at ntep.org.

Rust is a fungi and there are fungicides that control it, but we generally recommend that you let the disease run its course. It usually goes away by itself. You may want to treat on sensitive areas, such as sports fields if it becomes necessary.

These plots will be on the tour at the turfgrass field day this Thursday, July 24.

Category:

iaTURF Blog

Tags:

rust, disease, perennial ryegrass, Larry Ginger, American Lawn Care

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