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GRAY LEAF SPOT IN CENTRAL IOWA

October 2, 2012

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.

 

 

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ANOTHER GRAY LEAF SPOT WARNING

September 4, 2012

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. 

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GRAY LEAF SPOT DID SHOW UP IN CENTRAL IOWA

September 19, 2011

On August 31, I posted a blog titled "Watch Out For Gray Leaf Spot".

It did show up.  Here is a post from Cory Johnson, Superintendent of Cedar Pointe Golf Course in Boone, Ia.  This is Gray Leaf spot.  It showed up on September 8.  These pictures are from Sept. 16.  This is classic Gray Leaf Spot on perennial ryegrass fairways.  They will need to reseed with ryegrass as soon as possible.

If anyone else has experienced this, send me some pictures.  I suspect that there is more out there.

The first two pictures are fairway shots.  It is the rye that died and there is some live Kentucky bluegrass.

Picture 3 shows a close up of live bluegrass in dead rye.

Picture 4 shows leaf symptoms on the rye.

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WATCH OUT FOR GRAY LEAF SPOT

August 31, 2011

Those of you who have been around since the 90's will remember a major outbreak of Gray Leaf Spot on perennial ryegrass in 1998. This disease is caused by the fungi Pyricularia grisea. It seems to selectively hit perennial rye. Under the right conditions, it can be more devastating than Pythium blight. Like Pythium, it can kill large areas of turf over night.

In 1998, it wiped out perennial rye from Chicago to the Rocky Mountains. It was particularly hard on ryegrass golf course fairways and sports fields.

The conditions that set it off in 1998 were unusually high temperatures around Labor Day. We have not seen a major outbreak of this disease in 13 years, but tomorrow it is predicted to reach near 100 F. That is very hot for Iowa in September. If you have perennial rye that has not been treated with a fungicide, you may wan to be on the look out for this problem. Banner/Daconil was particularly effective against Gray Leaf spot in the 1998 outbreak, but there are other materials labeled for it as well. Check the label before you spray.

The pictures below were taken in 1998 on Willow Creek Golf Course in Des Moines. The dead grass is perennial rye. The only living grass is Kentucy bluegrass that was intermingled in the fairway and some patches had been used to sod around some of the heads.

Let me know if any of you see this in the next few days. Send some pictures if you do.

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IT'S BILLBUG TIME AGAIN

August 15, 2011

Right on schedule, the billbugs are back again this year. It is late July and early August each year that I get calls to come and look at lawns that look like they are "sick". The lawn below is in Gilbert, IA. While there is some leaf spot on this site, much of the damage was caused by billbugs.

The billbugs overwinter as adults. The adult female uses its bill (feeding mouth part) to burrow into the sheath just above the crown of the grass. She then deposits an egg in the sheath where it is is safe from most insecticides. This usually takes place in late April or early May. The egg hatches in July and the larvae proceeds to eat through the crown and to emerge into the soil. (The two pictures below are commercial slides from the American Society of America slide set on turfgrass insects)

To diagnose the problem, reach down and pull up some of the dead grass. If it is bill bugs, the grass will break away at the crown. The remaining tissue will be hollowed-out at the base.

Dig down into the soil and there will be many hollowed-out stems and a saw-dust like material left behind by the feeding larvae.

In early August, there will likely be larvae present in the soil

The larvae not very big. The picture below shows one on the tip of my pocket knife.


The larvae will soon turn into pupa and then into adults. This picture from the research station shows a larvae and an immature adult together in the same location.

The first question that I usually get from the home-owner is, "should I spray in insecticide now (in August)". The answer is no. The damage is already done and the application of an insecticide after the damage has occurred is not going to help. You have to treat the adult females in the spring before they lay their eggs. Late April is the best time to treat, however, that is difficult because they is no apparent damage at that time of year. You are also unlikely to see many adults at the that time of year.

There are systemic insecticides that could potentially be used when the larvae are in the sheath. The problem with that is that you do not see the damage before it is too late to treat.

This is a difficult pest to deal with because of these complex timing issues. If you have had a bad outbreak this year, it would be wise to invest in an insecticide application in the spring. Lawn care companies can do this, or the home-owner can do it themselves. Look for a insecticide that lists billbugs on the label. The critical thing is timing. If you apply after the eggs have been laid, you are wasting your time and money.

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MORE LEAF SPOT DAMAGE

July 29, 2011

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.

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LEAF SPOT EVERYWHERE

July 26, 2011

Yesterday, July 25, I began to notice a lot of damaged grass around campus and around Ames. This was not unexpected because of the extreme weather that we have had lately. We are nearing records for days over 90 F, followed by 70+ F nights with sufficient moisture to keep the turf green. This is ideal conditions for several diseases.

The problem appears to be Leaf Spot caused by the fungal organism (Drechslera poae). The old genus name for this organism was Helmintosporium, a name that still in use by much of the industry. This disease is common at this time of year, particularly when the spring has been wet.

So, if you have this problem, what should you do. There are a number of fungicides labeled for this disease, but usually we let it run its course. The area should recover later in the season and through the fall. Notice in the last picture that the new leaves are emerging in a healthy condition. I am expecting full recovery by September.

The first three pictures below shows leaf spot on central campus at Iowa State. It has now gone into the crown and root stage and the damage is quite apparent.

Damage just outside of Horticulture Building.

Beardshear hall just off of central campus.

Individual leaf showing lesions.

It is typical of this disease to damage older tissue first. Notice that the newly emerging leaves are health.

Here is an additional picture that I took yesterday afternoon on my own lawn.
In the area where afternoon shade cools the Kentucky bluegrass, there is very little leaf spot. In the area that gets the stress from the afternoon sun, there is considerable damage from leaf spot.

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