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Summer chugs along




A short break from the rain and storms!


After a series of days where we had not one, but TWO thunderstorms every day, the weather over the past couple of days has been pretty calm. Yup, for several days straight we had an inch or more of rain in the gauges in our yard, and last weekend there was a storm with gusts up to 80 mph. Some tree limbs were knocked down onto the powerlines in my neighborhood and power was out for 8 hours. Jim mentioned storms up his way that might blow them to Oz. Well, we just about sent Dorothy and Toto windborne up to Wisconsin.


Yesterday the highs were in the mid-80's which was a nice break from the mid-90's. However, today and tomorrow will be smokin' again...

... just in time for the Country Stampede.

What is the Country Stampede? Our quiet town of Manhattan, KS, population ~50,000, grows by 100,000 for a 4-day music festival

http://www.countrystampede.com/

It's ALWAYS hot and it ALWAYS rains, turning the campground into a muddy mess that looks more like a refugee camp to me, but instead of refugees it is full of sunburnt, drunk or hungover (depending on the time of day) country music fans having the time of their lives. (Yes, there's plenty of wholesome family fun, too.) It's not my cup of tea, but I hope everyone there has a fun and safe time. Sunscreen people! Sunscreen!

So, since the Stampede is here, my forecast is that there is a 100% chance of rain this weekend.


There is definitely still some brown patch action out there. I have not personally seen any Pythium blight yet but I suspect a few folks are getting hit with the heat, humidity, and high nighttime-lows recently.


Bentgrass trial:

Here at K-State we are participating in a multi-state trial of different cultivars of creeping bentgrass. The "susceptible check" is Crenshaw, and several other cultivars are in the trial, including Declaration as an example of a newer, less susceptible cultivar.

Like the other sites, we have the cultivars at both putting green and fairway height. The next set of photos shows some recent dollar spot activity in the fairway height plots. The cultivar plots are 5 x 10, and half of each (5 x 5) gets treated, the other half not.

(Click to enlarge)

Plot view, and lesion:













Along with turf problems there are plenty of landscape ornamental diseases right now. If you deal with ornamentals on your course, you might be interested to read on:


Iris leaf spot

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Zooming in closer on those lesions you can see dark structures which are the fruiting bodies (spore-producing structures) of the fungus:

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This disease is very common on iris. It is caused by the fungus Heterosporium. Removing and getting rid of old leaves in the fall will help to break the disease cycle, as the fungus survives winter on old, infected leaves. There are also fungicides available, but the sanitation aspects are key.

Rose rust

upper leaf surface:

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Close-up of underside of leaf:

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Those dark specks that look like seeds are spores. More specifically, they are called teliospores. The orange ones are urediospores. Here they are in even closer view:

rose_rust_spores

Roses vary in their susceptibility to rose rust. Starting with a resistant cultivar is a key first step. Then, like many other diseases, rose rust is favored by wet conditions. The fungus requires 2-4 hours of leaf wetness for infection to occur. The plants where I got these samples is on the north side of a building where there is a lot of shade:

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Shade = more leaf wetness = more disease.

“The Case of the Disappearing Mildew”

In plant pathology we have a concept called the disease triangle which is a way of remembering that for an infectious disease to occur, we need a susceptible host, an environment conducive to disease, and a virulent, viable pathogen. For managing diseases we can change these elements such as using resistant cultivars, changing the site to be less favorable to disease, and using various techniques to attack and avoid the pathogen itself.

disease_triangle

Check out this photo (click to enlarge):

disease_triangle_no_powdery

The white circle indicates a choke cherry that has been hammered, without fail, with powdery mildew every year since I got here–2006, 2007, 2008, 2009. This summer… no powdery mildew! What is going on?

Well, where I put the dashed yellow line there used to be a dense row of plants along the fence. Then, the orange line indicates another area that used to be a lot denser. All that plant material used to make a pocket with very little airflow. The newly-opened site is less humid, and now there’s little to no powdery mildew.

The host is the same. You can bet your bottom dollar that the powdery mildew fungus is still around. But, the site (environment) is much less conducive to mildew now.

Speaking of powdery, there is no shortage of it in other sites!

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3 Responses to “Summer chugs along”

Anonymous said...

I'm curious, what exactly is the objective in the creeping bentgrass cultivar trial?

Megan said...

Thanks for the comment. I should have included more info. We are comparing the dollar spot susceptibility of the different cultivars. Looking at the unsprayed plots is one piece of information.

Then, we are using a threshold based approach on the sprayed side, using Declaration as the indicator. That is, when dollar spot is > 5% in the putting green or > 10% in the fairway, we apply. We can then quantify the differences in dollar spot susceptibility in a managed system, too.

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