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An Instant Classic, Kentucky Bluegrass decline, and a Big Storm

July 19, 2010

The Open Championship concluded over the weekend with first time major champion Louis Oosthuizen running away from the field for the victory. With three of the four majors completed the summer is off and rolling.

The Field Day Classic was held last week at Jewell Golf and Country Club. It was a great day despite the heat with temperatures reaching into the high 90’s and a heat index well over 100. The course was in great shape and the weather didn’t seem to hinder low scoring. Special thanks to Brian Abels and his entire staff for hosting and putting on a great event.







The hot temperatures have also been causing havoc to our cool-season turfgrasses as well. Soil temperatures are now reaching into the low 80’s causing root growth to stop. Research has shown that creeping bentgrass generally loses about three quarters of its root biomass from the end of May to the beginning of June. This natural root decline coupled with the extreme rainfall amounts during the month of June which caused roots to pull back has resulted in turf that is especially sensitive to environmental and fungal stresses.

I have seen Kentucky bluegrass beginning to decline over the last couple of weeks. The pictures below show a low-mow Kentucky bluegrass intermediate rough. After inspecting the area, the decline seemed to be the result of leaf spot/melting out disease. The disease activity was also more prevalent where the turf was under shade part of the day. Notice how the common type Kentucky bluegrass in the primary rough remains largely unaffected. Mowing height also appears to be playing a large role in the disease activity. Leaf spot can be controlled on a curative basis but applications are most effective in the early stages of the disease.









Diseases will continue to wreak havoc on our cool-season grasses the rest of the summer. For those of you with large acres of perennial ryegrass, the prime window for gray leaf spot is right around the corner.

On a side note, Ames and central Iowa had severe storms roll through Saturday night with winds reaching speeds of over 70 mph. While I kind of like severe weather I do not enjoy the cleanup. Waking up Sunday morning it looked like a bomb had went off in the neighborhood with plant debris and trees down everywhere. Luckily the picture below wasn’t from my house but wasn’t too far away. Hopefully the rest of you in central Iowa were able to avoid damage as well.




June 10, 2013

Conditions have been very wet in the Midwest this spring, which has resulted in a very fast growth rate of turf.  Most of us are having a hard time keeping up with mowing.  These wet conditions in spring are often followed by a leaf spot breakout in turf.  The picture below is from the Chicago area.  It shows the typical leaf spot symptoms on fairway bent.

Symptoms generally include blighting from the tip down on bent, rather than the standard leaf spot lesions seen on other species.  The turf on the area may also look like it is dry, even if the soil is wet.  The grass also takes on a brown "haze" when you look at it from a distance.

The fungi that causes this is usually attributed to Bipolaris or Dreschslera (formerly Helminthosporium), depending on the author.  I will let the pathologist sort that one out.

Chlorthalonil (Daconil and other commercial names) is the standard answer for this problem, although there are several fungicides labeled for this disease.

This disease can also hit greens, but most golf courses are treating greens and it is not as common as it once was.  Because of the cost, fewer superintendents are treating fairways and that is where we are seeing most of the problem this spring.


Improving Accuracy of Disease Rating for Dollar Spot on Turf

September 27, 2010

The following is a post from a student named Steve Johnson. He is an undergraduate who was working for Dr. Mark Gleason on a pathology research project this summer. He is doing this as part of the requirement for his Hort 391 special studies course. Hopefully, this will start a trend and we will have several other posts like it this fall.

Steve Johnson, Soph. Summer Intern Blog #1

Many turfgrasses are susceptible to fungal diseases and this leads to many maintenance issues for turf practitioners.  In response to the detrimental effects of turf diseases caused by a wide assortment of fungi, a precise reading of the amount of turf infected by a disease is needed to determine the proper course of action.

In evaluating alternatives for suppressing turf diseases, its important to have a method to separate the effective treatments and the from the less effective ones.  This often requires replicated field trials, often at multiple sites, comparing each alternative in the same turfgrass stand.  But how, exactly, does one measure disease severity.

Disease severity is usually measured by some sort of visual estimation method.  In other words, you look at the turf that was treated with each respective fungicide treatment and try to visually estimate a number a represents how severe the disease symptoms appear.  This is not always accurate and may not be consistent from one rating to the next or from person to person.

As an example of this, lets consider the turf disease dollar spot, caused by the fungus Sclerotinia homeocarpa. Dollar spot is a relentless disease that is recognized by it distinctive lesions that are often the size of the a silver dollar and the lesions can grow together in severe cases.  Dollar spot is the most expensive disease to control on golf courses across much of the Midwest and Eastern United States.

In comparing dollar spot fungicide treatments to each other, how can we measure disease severity?  One way is to estimate the percentage of the plot that has turned brown due to the disease.  But one person rating the percentage of dollar spot may come up with a different number than someone else.  Others have two people rate the same plot independently of each other.  So how can we be sure that the disease ratings are consistent and reliable? 

Evaluating a way to accurately estimate dollar spot severity on greens-height creeping bentgrass was the objective of this study.  We wanted to find out how different two people would rate the same turf plots, and then average the ratings to reduce bias from individual ratings.  A trial was conducted during the summer of 2010 at the ISU Horticulture Research Station to evaluate dollar spot severity on creeping bentgrass.

The results of this study are mean to be relevant for disease severity ratings of many diseases and grasses, not just bentgrass and dollar spot.  


Examples of turf from the Hort farm plots infected with dollar spot.

1 and 2.

ISU Horticulture Farm turf plot marked out for the experiment. The white string was used to show where the corners of each were.  We then spray-painted the corners in order to visually locate where each plot was without the strings.  The strings were removed after all the corners had been painted so regular maintenance could continue.

WOI green located just north of Roy J. Carver Co-Lab on the northwest edge of the ISU campus.  It was marked out and prepared for the experiment in the exact same manner as the plots at the Research Station.