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K-State Turf and Landscape Blog

Author: kennelly

Dollar spot management, and resistance reminders

Posted on by kennelly

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

Aerification, part 2

Posted on by kennelly

Jared had a great post last week called Aerification… Some people love it, some think it’s a cuss word

There was a link to a nice USGA article about the benefits of aerification.

As a plant pathologist, I will second everything that is in there. I know, it’s hard to aerify when everything is looking awesome, but promoting drainage, getting organic matter under control, and encouraging root growth now will help prevent problems later (AUGUST!) when everything hits the fan.

Here is what we do NOT want.

Extreme puffiness:

puffy-and-hand-2 puffy-and-hand

Organic matter buildup (leads to poor drainage, heat retention, and roots crashing and burning in the summer):

organic-dark-layers putting-green-too-much-organic-matter-2010

Here are some of those sad roots:

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And, here is where those conditions led to Pythium root rot:

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Presentation1

Aerification can be a pain, but it can be a good friend.

aerification-holes-growth-may-2015 layers and aeration hole

Nozzles and water quality, you snooze you lose

Posted on by kennelly

Nozzles and water quality? Does that make you yawn?

Let’s start with nozzles

nozzle1

Spray nozzles might seem like a boring topic, but as stated in an article by Shepard, Agnew, Fidanza, Kaminski, and Dant in 2006 in Golf Course Management, nozzles are “The last piece of equipment through which sprays pass before contact with the turf.”

Think about the cost of all that stuff going through the sprayer, the time of the person applying those materials, and the fuel to power that sprayer (unless it’s a hand-sprayer, in which case I guess you count the cost of the donuts to feed that person walking around). Nozzles are small, and they don’t cost much, but they can really contribute to the success of an application and help maximize the bang for your buck on all those OTHER costs.

(Gee… I really need a donut!)

megan donut

Anyway – as noted in the article cited above, nozzles determine the amount of chemical applied, the uniformity of the application, the coverage, and they can influence the risk of drift. Make sure you calibrate your equipment, replace worn nozzles, and follow all label instructions about application equipment for the materials you are spraying. A worn-out nozzle could easily be allowing 10% or more excess material to be applied, which = 10% more money. Equipment that is not calibrated right might be applying LESS than you need to get adequate control.

Okay – now onto water quality.

Water quality? Snooze?

I just said that nozzles are the last thing to touch the materials before it goes soaring through the air and smacks into the plant. Water? That’s the stuff that cozies up with the product as soon as it hits the tank and stays with it the whole way.

Pop quiz – Which of these can affect pesticide performance?

  • Water pH
  • Water hardness
  • Dissolved minerals
  • Suspended solids

Or – you guessed it – all of the above.

Do you know what the pH of your water is? When is the last time you tested it?

There is an excellent publication on The Impacts of Water Quality on Pesticide Performance from Purdue. It is an easy read that discusses these factors with some pointers about testing. For example, pH can be testing using easy at-home test strips.

Be sure to follow all label instructions about water quality. Some pesticides are very sensitive to high pH, for example.

Don’t forget about some of those basic nuts and bolts, like nozzles, calibration, and water. If you don’t test them out now and then, there could be problems lurking that you don’t know about.

 

Spring fertilizer won’t make large patch worse

Posted on by kennelly

Can I fertilize my zoysiagrass now? I’m seeing large patch.

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Large patch is caused by Rhizoctonia solani AG 2-2LP. Brown patch of cool season turf is caused by closely related strains of R. solani. We know that fertilizer during brown patch season will enhance disease.

So – does spring fertilization increase the severity of large patch?

KSU collaborated with Dr. Lee Miller at University of Missouri to answer this exact question. The paper was just published in Crop, Forage, & Turfgrass Management and the abstract appears HERE. One of the authors, Ross Braun, worked on this project as part of his M.S. project.

At both sites, we applied fertilizer (calcium nitrate, ammonium sulfate, or urea) when the 5-day 2-inch soil temperatures reached 60 or 70ᵒF in spring or fell to 70ᵒF in fall. On those dates, the turf received 0.75 lb N/1,000 sq feet. Those treatments also received some summer nitrogen, too, with 0.25 lb N/1,000 in each of June, July, and August. So, all treatments received a total of 1.5 pounds N/1,000 sq feet/year. These early spring, late spring, and fall treatments were compared to summer-only controls which also received a total of 1.5 lb N/1,000 sq ft applied as 0.5 pounds in each of June, July, and August. We measured percent green cover using digital image analysis. Both studies were done in the cultivar ‘Meyer’ at fairway height.

Image of plot, and digital image with green pixels captured:

example example-reverse

The grand summary is that the spring fertilizer applications at either 60 or 70ᵒF did not lead to higher large patch severity compared to the standard summer-only treatment. This builds on and confirms prior KSU work by PhD student Ken Obasa  (click HERE for the abstract of the publication) where we also found that spring applications did not enhance disease, though in that study we did not use defined soil temperature thresholds. In that study we found that spring and fall fertility sometimes had greater green color than summer fertility treatments.

Right now in Manhattan, our 2-inch average soil temps are in the low to mid-60’s, so we are in the range where those spring fertilizer applications were shown to be “safe.” We did not look at fertility at temperatures lower than that. So, you should be in the clear, and a little N may boost green color and help you grow out of the disease symtoms.

What about nitrogen source? On some of the rating dates at both sites, disease severity was higher in plots treated with ammonium sulfate compared to other sources. The effect was not huge, but was significant, so you might want to shy away from ammonium sulfate if you have some large patch at your site.

Dr. Miller’s program is following up with even more studies to hone in on large patch and cultural practices, so we will stay tuned to see how those turn out.

Rose black spot

Posted on by kennelly

Hey, what are those black spots on those roses?

IMG_4003

You might have guessed, it’s “black spot.”

Here is some great information from Ward Upham:

Blackspot of Roses  
    A common disease of roses is blackspot, a fungus disease that can cause defoliation of susceptible plants. Look for dark, circular lesions with feathery edges on the top surface of the leaves and raised purple spots on young canes. Infected leaves will often yellow between spots and eventually drop.
    The infection usually starts on the lower leaves and works its way up the plant.  Blackspot is most severe under conditions of high relative humidity (>85%), warm temperatures (75 to 85 degrees F) and six or more hours of leaf wetness. Newly expanding leaves are most vulnerable to infection. The fungus can survive on fallen leaves or canes and is disseminated primarily by splashing water.
    Cultural practices are the first line of defense.
    1. Don’t plant susceptible roses unless you are willing to use fungicide sprays. For a list
of blackspot resistant varieties, go to: http://www.ppdl.purdue.edu/ppdl/weeklypics/3-22-04.html
    2. Keep irrigation water off the foliage. Drip irrigation works well with roses.
    3. Plant roses in sun in areas with good air movement to limit the amount of time the
foliage is wet.
    4. Remove diseased leaves that have fallen and prune out infected rose canes to minimize inoculum.
    If needed, protect foliage with a regular spray program (10- to 14-day schedule) ) of effective fungicides. Recommended fungicides include tebuconazole (Bayer Disease Control for Roses,Flowers and Shrubs), myclobutanil (Immunox, Immunox Plus), triticonazole (Ortho Rose & Flower Disease Control) and chlorothalonil (Broad Spectrum Fungicide, Garden Disease Control, others).

Here is a closer zoom of some of the spots.

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If you really look closely (or, in real-life, use a hand-lens) you might see tiny little bumps. Those bumps are the structures where the fungus produces its spores. Zooming in closer, with the help of a compound microscope, we can see the individual spores. Each spore can cause a new infection.

black-spot-spores-2