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Rain, Rain, Go Away

July 6, 2010

The 4th of July weekend brought rain across much of the state adding moisture to already saturated soils. Many parts of the state received upwards of 10 inches of rain for the month of June. Des Moines received 13.41 inches for the month which is well beyond their average of 4.57 inches. This ranks as the 4th wettest June on history, right behind 2008 when central Iowa received 13.45 inches. The average daily maximum temperature of 83.7 was slightly above the average of 81.8. The slightly above average temperatures coupled with the abundant rainfall provided plenty of opportunity for diseases.

The extreme wet conditions were especially conducive for slime mold development. In fact, slime mold often appears after heavy rains that were preceded by periods of dry weather (sound a little like our transition from May to June?). The slime mold I observed appeared overnight on a putting green following a couple days of rain. While slime molds are aesthetically unappealing, they are generally not harmful to the turf.

Most textbook and web references will describe symptoms of slime mold as round pustules that cover the leaf blade. The pustules can range in color from white, gray, purple, yellow, or orange. The bright colored pustules may appear first before turning darker in color, often within a few days. However, these descriptions best characterize the symptoms as they appear on taller mown turf. As you can see from these pictures, the symptoms of slime mold on green height turf appear slightly different from what is normally described.

These samples were collected shortly after the morning mowing. It is likely that the pustules were present but were smashed and smeared by the mowers. At quick glance while walking across the green, the mold resembled grease that had been tracked from the mowers but appeared in a random fashion. A microscopic view shows the black pustules covering the ends of the grass blades.

Because slime mold is usually short-lived and do not cause damage, fungicides are generally not recommended. Cultural controls normally include

washing the pustules from the leaf surface with water. However, given the excess moisture that can accompany slime mold, removing the pustules by gently brushing the turf may be a better alternative.

Let's hope we get a break from rain this week.

Marcus Jones
Graduate Research Assistant

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The Floods of 2010

August 13, 2010

This is a week that people in Central Iowa will not forget for a long time. Ames received around 10 inches of rain in a three day period and the city experienced arguably its most devastating flood ever. The Squaw Creek and Skunk River are the two major waterways that run through town. Squaw Creek crested at 18.13 feet (flood stage is 9) which was just shy of the record crest of 18.5 experienced back in 1993. The Skunk River crested at 26.52 feet (flood stage is 20) which was above the 1993 crest of 25.53 feet. For those familiar with Ames, the picture above is a shot of Hilton Coliseum inundated in flood waters.

The majority of the flood waters have now receded and cleanup efforts are well underway. Trying to predict the survival of turfgrass in flooded conditions is tricky business and depends on so many factors. Weather is a big factor and has not been on our side so far this week. Temperatures have been in the low 90’s with the humidity pushing heat indices into the 100’s.

We were greeted to a healthy dose of mycelium at our research station this morning. During my time spend in industry, I learned that trying to visually distinguish between dollar spot and pythium blight is very difficult (at least it is for me!) so we brought the sample to campus for a closer look. Inspection of the sample under a compound microscope confirmed that the disease we were seeing was in fact Pythium blight.
 

 

We also stumbled upon some slime mold. Earlier in the year we had a post about slime mold on green height creeping bentgrass. This slime mold appeared on rough height Kentucky bluegrass. Remember that slime molds are more of an oddity, they’re unsightly but they are not considered harmful and control measures are not necessary.

I’ll leave you with a video courtesy of KCCI News Channel 8 showing an aerial view of the city this past Wednesday morning.

https://www.youtube.com/watch?v=YQSnfvRw8mU

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SLIME MOLD-2018

June 29, 2018

It is Slime mold time again in central Iowa and I have had several questions on it in the past week.

Wet weather increases the occurance of slime mold in turf.  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.

 

I have attached two new pictures from this week.  The first is from Larry Ginger of American Lawn Care in Des Moines.  The second is from Bruno Novotny who works at a course in Forest City.

 

 

 

The others, come from an older post on slime mold (June 4, 2013)

 

 

 

 

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SLIME MOLD SHOWING UP ON TURF

June 4, 2013

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.

 

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