Search results

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.
 

On September 4, I put up a post warning that Gray Leaf Spot might show up in Iowa because of the unusually warm conditions around labor day.

On the 4th I wrote the following:
"This disease is caused by the fungi Pyricularia grisea. It seems to selectively hit perennial ryegrass on intensely managed areas such as golf course fairways and sports fields. Under the right conditions, it can be more devastating than Pythium blight. When it hits, it can wipe out large areas of turf overnight.  Fungicides, such as Banner/Daconil will control it, but they must be applied before the outbreak.  Once the disease begins, it is too late to apply.  The reason I bring this up is that we are in the same weather pattern again this year.  The disease does not always occur when its hot around Labor Day, but it did last year and I would watch for it this year".

What I didn't know at the time was that it would be me that would get hit with the gray leaf spot.  When I went out to take data on the perennial ryegrass trial at the research station in mid September I found that the ryegrasses in the trial appeared to have collapsed.  They looked terrible.  I then looked at two other areas of perennial ryegrass on the site and saw that it looked the same.  Andrew Hoiberg, who recently graduated with his Ph.D. was at the station at the time and commented that it looked like gray leaf spot.  On closer inspection, that is what it appears to be.  It was right on time, shortly after Labor Day during an unusually warm spell.

This trial is part of the national turfgrass evaluation trials (NTEP) and we purposefully do not treat it with fungicides.  The damaged cultivars are beginning to show some recovery as of the beginning of October, but they are still showing signs of the damage.  Under normal conditions, we would simply reseed into the ryegrass and we would have it back in a couple of weeks.  We are unable to do that here because of all the different varieties that are involved.  We will have to wait for recovery.

By the way, is it Gray Leaf Spot or Grey Leaf spot?  You will see many examples of each if you search the internet.  I'm using Houston Couch's book as my source and going with Gray.

The pictures below are of the site in mid September when the damage was most severe.  The first three are of the NTEP perennial ryegrass trial.  The last four are closeups of the damage.

A year ago, on August 31, 2011, I put up a post warning about Gray Leaf Spot on perennial ryegrass.  This disease shows up rather infrequently in Iowa, but it does occur around Labor Day on years when temperatures are unusually high.  Last year's Labor Day temperatures were in the 90's and if you check the post from September 19, 2011, you will see that it did occur on several golf courses with perennial ryegrass fairways.

This disease is caused by the fungi Pyricularia grisea. It seems to selectively hit perennial ryegrass on intensely managed areas such as golf course fairways and sports fields. Under the right conditions, it can be more devastating than Pythium blight. When it hits, it can wipe out large areas of turf overnight.  Fungicides, such as Banner/Daconil will control it, but they must be applied before the outbreak.  Once the disease begins, it is too late to apply.

The reason I bring this up is that we are in the same weather pattern again this year.  The disease does not always occur when its hot around Labor Day, but it did last year and I would watch for it this year.

The pictures below were taken in 1998 on Willow Creek Golf Course in Des Moines and last year on Cedar Poine golf course in Boone. The dead grass is perennial rye and living grass is Kentucky bluegrass.

If anyone has an outbreak of Gray Leaf Sport this year, let me know and send some pictures. 

This is a follow up to my post of July 26 on leaf spot damage. By the way, I added a picture of my own lawn at the end of that post. Those of you with leaf spot in turf are not alone.

Yesterday, the 28th, I was asked to look at some lawns in the Polk City and West Des Moines area. What I saw was a lot more leaf sport damage.

On the lawns below, the entire subdivision had been irrigated during the early summer. Just before the heat, the irrigation system went down for a few days. We are just coming off of nearly two weeks above 90F. Some days reached 99 and 100. This is ideal conditions for leaf spot to develop. Even lawns that had irrigation in surrounding areas showed a lot of damage.

At this site, there was a clear pattern. It was the areas exposed to the sun, particularly south facing slopes that showed the greatest damage. This is very severe damage, but it will recover. Typical of leaf spot, the older leaves have died, but the new growth appears to be healthy. I recommended that they fertilize about the 15th of August and I predict that most of it will recover by October.

This is a south facing slope, and it shows some of the worst damage.

This is a very interesting picture. The foreground is a south facing slope. The background, which is on the same irrigation system and received the same treatments and mowing as the lawn in the foreground shows very little damage. The difference is that the background is a north facing slope that was protected from afternoon sun by the houses and by the slope.

Should you apply fungicides at this time? Damage is already done and recovery is beginning to take place. I don't think that fungicides would be worth the cost at this point.

This was a convergence of just the right conditions for this disease to occur. Hopefully we will not see damage this bad again for a few years.

This is the first of the 2011 research reports. It includes the 2010 results from our trial on creeping bentgrasses maintained at both fairway and green height. Tables 3 and 4 are jpg photos and you will need to click on them to be able to read them.

Creeping Bentgrass Dollar Spot Study

Christopher J. Blume and Nick E. Christians

Objectives

The objectives of this study are to determine the susceptibility of creeping bentgrass (Agrostis stolonifera) cultivars to dollar spot (Sclerotinia homeocarpa) under both green height and fairway height.

Materials and Methods

This fairway height (0.5”) and green height (0.25”) studies are being conducted at the Iowa State University Turfgrass Research Station it is part of a regional project being conducted at several of the Midwestern Universities. Both studies included 24 cultivars, although some of the cultivars differed on the two sites (Table 1). The green-height study area was established on a sand-capped area, and the fairway-height area was established on a native soil area (Nicollet clay-loam).

Both studies were established 17 September, 2008. The plots were allowed to mature until the spring of 2009. The plots were then split into untreated and fungicide treated halves. The study was conducted as a randomized split block design, with three replications.

Fungicide treatment timing was based on the cultivar ‘Declaration’, which is the most dollar spot tolerant cultivar in the study. Treatments were made to the green height plots when ‘Declaration’ was observed to have at least 5% of the plot area infested with dollar spot. The fairway height study area was treated when ‘Declaration’ was observed to have at least 10% of the plot area infested.

The fungicide mixture consisted of Emerald (0.18 oz product/1000ft²) and Daconil Ultrex (3.2 oz product/1000ft²), applied in 2 gallons water/1000ft². The applications were applied using a modified spray boom, with two TeeJet XR flat fan nozzles. In 2010, three applications were made 24 June, 19 August, and 4 October.

Results

‘Memorial’ and ‘Penncross’, and ‘LS-44’ had the best quality ratings in the green height study in 2010, whereas ‘Allister’ received the lowest rating. In the fairway height study, ‘Alpha’, ‘LS-44’, and ‘Memorial’ were the highest rated cultivars, and ‘Independence’, ‘Declaration’ and ‘SR 1150’ received the lowest quality ratings (Table 2).

‘Century’ and ‘Imperial’ showed the most damage from dollar spot in both September and October in the green height study (Table 3). ‘Memorial’, ‘Declaration’, and ‘Crystal Bluelinks’ had the least damage in untreated plots at the end of the season.

There was not as much dollar spot in 2010 as there was in 2009 on the fairway height bentgrass. At the first two ratings of the season, there was more dollar spot in the treated side than in the untreated side of the plot. These plots had not been treated since the fall before. The reason for this observation is unknown. In August, no dollar spot was observed on treated or on untreated sides of the plot. In September, ‘Southshore’ and ‘Century’ had the most dollar spot on the untreated side of the plots, whereas ‘Memorial’, ‘Independence’, and ‘Declaration’ had the least dollar spot. In October, ‘Crenshaw’ and ‘Century’ had the most dollar spot and ‘Memorial’, ‘Alister’, ‘Pennlinks II’ and ‘Memorial’ had the least (Table 4).