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K-State Turf and Landscape Blog

Author: kennelly

HOT! Soil temps and turf decline

Posted on by kennelly

(Megan Kennelly, KSU Plant Pathology)

We all know it has been super hot lately. Yuck! We humans are suffering because of the hot air, but our cool-season turfgrasses are suffering from the high soil temperatures.

I have not had an onslaught of samples yet, but I fear that if this weather keeps up, they will be coming soon. Usually the flood of turf comes in August, but this is shaping up to be a tough year. (If we are lucky, I’ll be wrong and the weather will chill out, the turf will chill out, and WE can chill out!)

I took a look at soil temperatures at the Kansas Mesonet website (click HERE to access it), and I saw that our 2-inch daily max soil temps in Manhattan have been soaring into the 90’s and our 4 inch daily max soil temps have been solidly in the mid to upper 80’s.

Pop quiz – do you remember the optimal 4-inch soil temperature range for root growth in cool-season turf?

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Got your guess?

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The answer – 50-65 degrees Fahrenheit. We will not be seeing that again for several months.

When we get into our current range of steamy 80’s and 90’s in the soil, root growth shuts down. Shoot growth is shutting down too. That means, if you lose cool-season turf now it will be very hard to get it back again.

Now, I’ll point you to some prior posts and references that outline some tips on summer stress management.

We sent these two last week, but I’ll post again here.

By Jack Fry: - general tips for water management:

https://blogs.k-state.edu/turf/good-water-management-will-help-get-greens-through-midsummer-stress/

By Dale Bremer - using moisture sensors:

https://blogs.k-state.edu/turf/water-management-on-greens-with-soil-moisture-sensors/

 

Here is another old post from last year:

Summer weather can be ruthless when the turf is stressed and rootless

And, finally, in this page, starting on page 6, there is an excellent, clearly-written set of tips on reducing summer stress in putting greens. Really – if you manage putting greens, take a couple of minutes, click here, scroll to page 6, and read these tips.

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

 

 

 

That’s not a disease! (Lacebugs on cotoneaster)

Posted on by kennelly

(Megan Kennelly, KSU Plant Pathology)

Brown spots are not always a disease.

We had a cotoneaster sample last week that looked like this:

damage-lacebug

The undersides of the leaves looked like this:

lacebug-frass-cotoneaster-branch

The submitter thought this might be a disease, but upon closer inspection we found these guys, lacebug nymphs. The shiny black stuff near them is frass (insect poop).

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Lacebug eggs:

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But, what else did we find?

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This is a laceWING egg. Lacewings are predators (good guys!), and they love to eat lacebugs!

I called my awesome colleague Dr. Raymond Cloyd to discuss this, and he confirmed that in general, lacebugs will not severely damage the plants. The damage is primarily aesthetic. And, the good guys (lacewings) were clearly in the area, doing their job. Dr. Cloyd’s advice was to let nature take its course. One “soft” option might be a hard spray of water to remove/reduce the lacebugs. That would also remove the lacewings, but the lacewings would come back.

Lacebugs (and many other insects!) are described in our publication: Tree and Shrub Problems in Kansas: Diseases, Insects, and Environmental Stresses. To get a copy of that publication, you can find the pdf HERE or you can order it by calling the K-State Research and Extension bookstore at 785-532-5830 where you can order a print copy for $9.70 + shipping.

 

 

 

 

Pythium foliar blight in ryegrass and bentgrass tees and fairways

Posted on by kennelly

(Megan Kennelly, KSU Plant Pathology)

I haven’t received any Pythium foliar blight samples yet, but I wanted to provide a heads up and reminder.

Pythium foliar blight, sometimes called cottony blight, is one of the most destructive turfgrass diseases.  The disease can explode in only a few days if conditions are right. Perennial ryegrass and tee- or fairway-height creeping bentgrass are the most common hosts in Kansas. Though Pythium root rot (caused by different species) is common in putting greens, Pythium foliar blight is rare in putting greens. In 10 years, I have seen it only ONE time on a putting green. Tall fescue, Kentucky bluegrass, bermudagrass, and zoysiagrass can become infected, but this is extremely rare.

Conditions for Disease Development

The risk of Pythium blight is highest during humid weather when day temperatures are 86 to 95 degrees Fahrenheit and overnight lows are consistently at least 68 degrees Fahrenheit.

The disease is most common when soils are saturated with water, due to excessive rainfall or irrigation. Long dew periods, high relative humidity, and lush, dense turfgrass growth also favors disease development. Low areas, sites with poor air flow, and sites with poor drainage are particularly vulnerable.

Symptoms

In fairway-height bentgrass and perennial ryegrass, the first symptoms are irregularly shaped, water-soaked, greasy patches up to 4 inches in diameter.

Pythium in rye fairway

If it is humid, a cottony growth may be present early in the morning.

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The patches may merge into larger blighted areas.

pythium 2006-2

The pathogen can be spread by equipment  and in water drainage patterns. Here is some Pythium blight at Rocky Ford a couple of years ago, following the pattern where heavy rain caused a water flow across this plot from left to right.

r ford pythium blight

Look-alikes: Pythium blight can be confused with brown patch, damage due to thick thatch, drought stress, or grubs. Brown patch is active during these same conditions. If you have any doubt, you can always send a sample to the diagnostic lab.

Management

Pythium thrives in water, so water management is the key to Pythium blight control. The following practices will reduce the risk of other diseases (and stresses), too:

  • Improve drainage in areas where water is likely to stand for any length of time.
  • Avoid overwatering, especially during hot, humid periods.
  • Promote rapid turfgrass drying by proper spacing and pruning of shrubs and trees.
  • Fans can improve airflow in closed-in areas where collars and approaches have a history of disease.
  • Irrigate in the early morning to reduce the number of hours of leaf wetness.
  • Excessive nitrogen fertilization stimulates lush growth that is more susceptible to Pythium blight. Maintain a proper balance of nutrients and avoid fertilizing during periods of Pythium blight activity.
  • If active mycelium is present, avoid mowing, which can spread the pathogen.

Preventive fungicide applications during the summer months may be necessary on perennial ryegrass or creeping bentgrass golf fairways.

Below is the Pythium blight fungicide information from Chemical Control of Turfgrass Diseases by Paul Vincelli and Gregg Munshaw at University of Kentucky. You can click the image below to zoom. For the full guide, visit HERE.

Kentucky-2015_Page_17

Weekly top pics from the diagnostic lab

Posted on by kennelly

Here are a few quick pics from the diagnostic lab. These photos were taken by our summer intern, Beth McKinzie.

Rose mosaic virus:

rosemosaic

Rose mosaic virus is caused by several viruses, sometimes in combination. There is no control for this disease once the plant is infected. Diseased plants are not killed outright but may have reduced vigor and are more prone to winterkill. Symptoms are most prominent on new growth in spring. The virus is spread by propagation practices. Remove and destroy affected plants.

Sycamore anthracnose:

sycamore-anthracnose

Anthracnose diseases affect several tree species in Kansas. Anthracnose causes brown irregular leaf spots, often along veins. Premature leaf shedding and twig blighting can also occur. Symptoms develop during wet spring weather. Anthracnose is rarely damaging and primarily cosmetic, with no management needed. Trees usually produce new foliage and recover with the onset of warmer, drier summer weather. For more on anthracnose in shade trees, you can read more HERE.

Bacterial wetwood:

wetwood

Wetwood is caused by multiple species of bacteria that reside inside the tree. It is common in elm, cottonwood, maple, mulberry, oak, willow, and sycamore. Liquid oozes from wounds and cracks and runs down the bark, leaving discolored streaks on branches or trunks. This is primarily cosmetic and no management is needed.

Season-long agronomic practices to reduce anthracnose risk in putting greens

Posted on by kennelly

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The temperature dial is getting turned up, and summer stress is on the way. Unfortunately summer is often when we are sometimes pushing greens even further with low mowing heights for tournaments, etc.

Over the past few years, Rutgers University has led a multi-university research program to investigate the impact of cultural practices and fungicides on turfgrass anthracnose, including fertility (it’s really important!), mowing height (even a small increase can help!), and more.

We have some more information about anthracnose (including fungicide info) HERE.

The BMP’s from Rutgers are outlined HERE.

If you just can’t get enough, details from Rutgers are available HERE (you can click through a 54 page pdf with lots of images and data)

Here is a cheat-sheet of some tidbits from the above links about agronomic practices and anthracnose:

Fertility program: Provide adequate nitrogen to maintain turfgrass growth. Low nitrogen can increase anthracnose severity. Applications of soluble N at 0.20 to 0.25 lb N/1000 square feet every two weeks is beneficial. Apply adequate potassium.

Mowing and rolling: Low mowing heights can raise the risk of anthracnose development. Slight increases in mowing height can reduce disease pressure. Consider raising the mowing height to 3.6 mm (0.14 inches). Rolling on alternate days will increase ball roll and can slightly reduce anthracnose severity.

Irrigation and drainage: Anthracnose can be more severe with either too much or too little water. Irrigate to supply 60-80% of evapotranspiration. Avoid wilt stress. Hand-water when practical. Anthracnose tends to be more severe on putting greens with poor air movement and poor drainage. Don’t overwater putting greens: excessive soil moisture may damage roots and decrease photosynthesis, predisposing it to anthracnose injury. Aerify in the fall to improve drainage, and improve airflow to the site.

Topdressing: Light, frequent topdressing reduces the overall risk of anthracnose.

Foot traffic: In one of the more recent Rutgers studies (link to article HERE by Joseph Roberts and James Murphy), they looked at foot traffic + sand topdressing, foot traffic – sand topdressing, no foot traffic + sand topdressing, and no foot traffic and no sand topdressing. The combination of foot traffic + sand topdressing had the LEAST amount of disease.

Plant Growth Regulators: Normal use of trinexapac ethyl and ethephon has reduced anthracnose in trials. Mefluidide has had little effect in most cases.

Cultivation: Shallow verticutting (0.13 inch) has had mixed results, leading to slight increases in disease in some studies and no effect in others. If anthracnose is active, use fungicides before any cultivation.

 

 

Pythium root rot in putting greens

Posted on by kennelly

Jared Hoyle mentioned that he has been getting some questions on Pythium root rot, and last week, our neighbor to the east Dr. Lee Miller at University of Missouri wrote in a great post (click HERE) that he has already seen some Pythium root rot samples from putting greens with all the wet conditions. Even in the absence of Pythium in the roots, heavy rains in spring = poor root growth = turf more likely to crash and burn when summer conditions kick in. Add Pythium and that can make it even worse. In his article, Dr. Miller also provided a caution that some of the materials superintendents apply in spring such as pre-emergent herbicides, DMI fungicides, and PGRs could be limiting root growth in spring and setting up the grass for more problems. His comment is observational from comments from superintendents but is definitely interesting and as he states, probably some research is needed.

In another excellent recent post from NCSU, Lee Butler provided some specific tips about management:

“We currently recommend that everyone start their Pythium root rot prevention program off with Segway due to it being very good in our trials over the past couple of years, even at the 0.45 oz/M rate. At the 0.45 oz/M rate, you can apply Segway 6 times instead of 3 according to the label, so you will want to rotate that in with other products like Subdue, Banol, Stellar, Appear, or Signature (in no particular order). For more information about Pythium root rot, click here. Any decent Pythium fungicide such as Subdue, Segway, Banol, Stellar, Appear, or Signature (in no particular order) should do a nice job of preventing this disease. You will likely have to make repeat applications every couple of weeks until the weather changes. Rotate through the different chemistries to help with resistance management.”

Finally, don’t forget that Pythium root rot is distinct from Pythium foliar blight. The foliar (cottony) blight is actually quite rare on putting greens. Foliar Pythium is definitely linked to warmer conditions, with nighttime lows > 68. For fungicide information on foliar Pythium, you can view the table HERE from U of Kentucky (scroll to p 17).

 

Slime molds!

Posted on by kennelly

Thanks to Ron Reese for sending in these great photos of slime molds! I’ve seen the purple-gray type before but I have not seen the orange one.

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Slime molds do not damage the turf. They do not invade the plant tissue – they eat bacteria on the surface. If they are a nuisance you can use a rake or broom to dust them away, or blast with a hose. Or, just keep them around as a fun conversation piece in your grass.

Slime molds will also grow in mulch, on tree stumps, and on other areas of the landscape.

slime_mold_yellow_mulch

“I’m not ready to be thinking about brown patch, Jack”

Posted on by kennelly

I was out at Rocky Ford this morning planning some projects with my colleague Dr. Jack Fry and our student Mingying Zhang. I was enjoying the clouds and thinking how lucky I am to be able to work outside at least part of the time… what a lovely morning…

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When, suddenly, Jack said, “I think there’s some brown patch over here.”

Sure enough – there it was!

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A closer inspection revealed the lesions:

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Brown patch likes moisture, and we’ve had no shortage of that. Brown patch also likes warm nights (temps about 68 or higher), and we have had a few of those in the past few days. So, there you go. I was not quite ready to be thinking about brown patch, but brown patch does not care what I think! Also, this was a newly-seeded stand (last fall) and it did just get a boost of quick-release N (for a study), so it was juiced up and susceptible. We didn’t see it elsewhere, in less-juicy turf.

Brown patch conditions will be fading, so symptoms in our plot will probably fade too.  The nighttime lows will be cooling off in the next days. For example, those lows will be in the low-mid 60’s (Kansas City area), upper 50s to low 60’s (Manhattan), and upper 50’s-low 60’s (Goodland), depending on which forecasting service you look at. With cooler temps, any brown patch activity should cease, but it may be back again when summer conditions kick in for good.

For more information on brown patch you can check out some information HERE.