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Dollar spot management, and resistance reminders

Dollar spot is active during temperatures of  65-85 F, and we definitely have had those conditions lately.

dollar spot

What to do? Rather than reinvent the wheel on describing potential management regimes, below is the dollar spot information from the excellent fungicide guide from University of Kentucky (for the full guide click HERE). (Oh I’m also excited to announce that one of the authors, Paul Vincelli, will be one of our speakers at the Kansas Turf Conference later this year).

But hold on – as an important side note – in a study at KSU a few years ago we found that 63 of the 65 dollar spot isolates (strains) we tested from across Kansas were fully resistant to thiophanate-methyl. (The study by my former M.S. student Jesse Ostrander was published HERE). Resistant isolates will grow through thiophanate-methyl like you didn’t do anything. I don’t think I know anyone relying on that material by itself for dollar spot, but this is just a heads up that resistance is definitely a problem for that product. I did have a conversation a year or two ago with someone using thiophanate-methyl plus a low rate of chlorothalonil and they had a lot of breakthrough. We did not test their isolates, but I’m guessing they had resistance to the thiophanate-methyl, and then the lower rate of the chlorothalonil was not enough to get them through the window they were hoping to cover. (Thiophanate methyl is a good product for some other diseases).

In addition, some of the other materials are at risk so be sure to rotate among mode-of-action groups. Some labels provide information about rotations.

What is YOUR dollar spot plan? Shoot me an email, or pop over to our Facebook account and leave a comment. I’ll share any great tips that you share.

Okay – now here is the guide. You can click the images below to make them bigger.

Kentucky-2015_Page_12

Kentucky-2015_Page_13

Recent turf problems – a few photos

(Megan Kennelly, KSU Plant Pathology)

It’s mid-July, and much of Kansas continues to be pretty wet. Here are some recent turf issues I’ve been seeing and hearing about. I won’t go into details – this is just a photo collection for now.

(1)Brown patch in tall fescue lawns.

When you get all sweaty just from dragging the trash can down the driveway out to the curb on trash day, you know it’s brown patch season. Here are some symptoms in my neighborhood.

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(2) Summer patch

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Summer patch is a root disease of Kentucky bluegrass. Infection occurs in the spring, when soil temperatures hit 65. Symptoms pop out in mid-summer, when those poor plants with their compromised root systems just can’t take it anymore.

(3) Dollar spot

Sometimes dollar spot checks out during the summer, if conditions are hot and dry. We’ve had enough warm/wet weather to keep it rolling. Here are some photos in Kentucky bluegrass as well as in creeping bentgrass, especially in highly susceptible varieties.

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(4) And, “it’s not a disease”

Turf sites with heavy clay soils, low areas with poor drainage, and shady sites = high stress. I received a sample the other day with some of the heaviest clay I’ve seen in awhile. It was so clay-ey that I took a moment to sculpt it into this little soil person:

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If your soil is heavy enough to use in art projects, you may have a problem. As you look forward to fall, think about aerification, drainage improvements, reducing shade, and other practices to improve conditions in tough sites.

A rainy spring meets a rainy summer. A cornucopia of turfgrass diseases

(Megan Kennelly, KSU Plant Pathology)

We are at the junction/transition of spring to summer. Large patch is still raging in the zoysiagrass. Dollar spot is active in bentgrass and other susceptible turfgrasses, especially in susceptible varieties. In addition, we’ve had some nights with lows in the upper 60’s or low 70’s, and that can mean brown patch activity. It’s a busy time for diseases. As one of my colleagues said, “It’s a fungusy sort of year here in Kansas.”

With all the rain, it’s been hard to keep up with the mowing. We are feeling it at Rocky Ford, with Cliff and the students busy mowing whenever they can sneak it in. And, it’s hard to spray fungicides when it rains every other day. I put out a trial this past Monday since it was the only day that looked clear. Good thing it was not on the agenda for yesterday, when we had 3 thunderstorms in the same day!

Large patch is still rolling in the zoysia:

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Dollar spot is active:

dollar spot

Brown patch might not be far behind:

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With all the wet, saturated soils there could by Pythium root rot as well:

Copy of pythium-bentrass-2006

(Pythium spores stained pink in the microscope).

As a final note, I’ve gotten some questions and photos recently about algae.

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Like other weeds, algae likes to take advantage of thinned out turf. Saturated soils and poor root growth can thin out the turf, and algae loves wet conditions. If you didn’t know where your drainage problems were, algal growth can point the way. There are some fungicides labeled for algae, but addressing the underlying site issues is key.

For a list of fungicides for algae, check HERE and go to page 7.

 

Heavy dollar spot pressure

This week is pretty hot, but overall its been pretty mild this summer. Dollar spot is most active at temps ranging from 59-86 and we’ve had a lot of temps in that range. We’ve also had some dewy mornings. Dollar spot often is at its most active stage here in Kansas during late August into September, with long, cool, dewy nights.  Make sure you stay on your game with your dollar spot management program. There are lots of tips and tricks in the dollar spot section of this guide:

http://www2.ca.uky.edu/agc/pubs/ppa/ppa1/ppa1.pdf

Here are some symptoms out at Rocky Ford:

The heat this week will increase brown patch pressure. I saw some of that today, too, but it was kind of faint and didn’t show up well in the pictures. But, it is definitely there, and lurking…. On the brown patch front, we will probably move permanently out of brown patch weather pretty soon and hopefully won’t have to worry about it any more until 2015.

Dollar spot activity

The moderate temperatures are reducing stress on our cool-season turfgrasses, and some of our typical late July/early August diseases are not active. Dollar spot likes this type of weather and it IS active. Here is a picture of a nontreated plot out at Rocky Ford:

Keep on your disease management plan, and don’t forget some back-to-basic things like calibration, swapping out worn-out nozzles, etc.  I spoke with someone recently where it sounds like some application/calibration issues might have compromised disease control.