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Tag: pythium

Pythium foliar blight

This yucky summer weather just keeps going. The past few days have been the most humid I have experienced in a while. Hot and humid = Pythium weather. We’ve mentioned foliar Pythium a few other times during this stressful summer of 2016. (As a reminder, foliar Pythium is distinct from root Pythium… which we’ve also discussed a few times!)

In the past we days we received a couple of samples of Pythium foliar blight (also called Pythium cottony blight). One was from a perennial ryegrass golf course fairway.

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In the photo above you can see the greasy, matted down appearance of the turf. With a handlens, or even just with the naked eye if you looked closely, mycelium was present. In the microscope it was clearly Pythium (see the tall fescue pics below).

Here are some shots of the ryegrass in the field:

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The second sample was from a tall fescue home lawn. Usually we think about Pythium on ryegrass or creeping bentgrass, but it can attack other cool-season turfgrasses. Tall fescue has more potential to recover than perennial rye or bentgrass. In 11 years, I have seen it on tall fescue only 1 or 2 two times before.

Below is a photo of the greasy, matted-down tall fescue turf. After incubating overnight in a plastic box with wet paper towel the mycelium was present.

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In the microscope, the pathogen was clearly distinguishable as Pythium.

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Just as a comparison, check out the strong crosswalls that are found in the brown patch pathogen, Rhizoctonia solani:

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Here is a shot of the site, where it looks like the Pythium was tracked along with a mower:

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The pattern is different from brown patch, and brown patch lesions were not present. I have seen weird tracking patterns with fertilizer burn or other chemical injuries, too. It can be challenging to know what is what. If you have any doubt, send in a sample, and email some photos.

Pythium thrives in wet conditions, so avoid overwatering. Water deeply and infrequently, and avoid watering in the evening. Improve drainage and try to increase airflow and sunlight. Avoid overfertilizing – Pythium loves an overly lush lawn. As a bonus, those practices will also reduce the risk of brown patch.

Pythium is not a true fungus, it is an oomycete. The most effective fungicides for Pythium are the ones specifically for oomycetes. There is a comprehensive list here, from the Chemical Control of Turfgrass Diseases publication from University of Kentucky (click the photo to zoom in):

Kentucky-turf-fungicides-2015-ppa1_Page_17

 

There is some more excellent information, photos, and management tips here:

http://extension.missouri.edu/p/IPM1029-17#Pythiumfoliarblight

 

Brown patch is still active out there (it’s a little faint in the pic, but it’s there):

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And dollar spot is active, too (mixed in with more brown patch):

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Root decline, it ain’t benign

(Megan Kennelly)

In the past 2 weeks we have posted a series of articles related to root health and rootzone management. I’m following up here with a few more photos (click to zoom any of the photos below).

Most of the samples have shown layering, thatch, and a build-up of organic matter.  These can reduce drainage, and roots suffer from lack of oxygen. Furthermore, wet soils hold heat, so the turf gets a double whammy of wet + hot. Steam-cooked turf is not happy turf. I’ve seen some very unhappy roots lately. Some have Pythium root rot as well, some appear to be in serious decline just from the physiological stress.

We already posted a bunch of information about managing rootzones and some tips on what to do in the fall and in the future, so I won’t go into that here. Glance back at our recent posts. You might also like to read pages 6-7 on the following website by Paul Vincelli and Gregg Munshaw which discusses managing summer stress in putting greens:

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

Here is some layering in several recent samples. I know it can be tough to convince golfers to let you aerify, but the consequences of NOT aerifying can be deadly when summer weather strikes.

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This is an older push-up green with drainage issues in all this wet weather:

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Here is a series of photos showing Pythium root rot and root decline symptoms:

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Here is a field shot of the site that goes with the microscope pictures above:

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Here is one more set of photos showing layering and decline. This site had root decline, Pythium root rot, algae, and some anthracnose crown rot. Those factors all like to co-mingle and cause problems. This superintendent said they are working on improving some drainage and rootzone issues that built up over time.

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