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K-State Turfgrass

Category: Diseases

Hydrangea Decline + Root Rot on Coreopsis

Wet then Hot….Hydrangea shrubs crash and burn

By: Judy O’Mara

At first glance, the declining hydrangea makes you think that they were wiped out by a disease. A quick check of the very useful K-State website (http://mesonet.k-state.edu/weather/historical) for historical weather data for Morris County (where hydrangea plants were grown) shows that it got 27.83″ of rain in the first half of the year (January 1 -July 7, 2019). Of that amount, almost 23″ (22.95”) of rain was received during April 29 –July 7th with several periods of 4-6″ over that ten week period. Basically that is a lot of rain.

The impact here is that lots of rain can keep soils wet and soggy, which in turn damages the root system. Plants with damaged roots may not have expressed symptoms during May or June because temperatures during that period were fairly moderate. More recently temps jumped into the 90s and damaged root system were unable to support the tops of the plant. Affected Hydrangeas crashed and burned. Mulch is generally a useful tool to help suppress weeds and keeps soils moist. Too much mulch over heavy clay soils can aggravate the problem by keeping soils too wet.  It can be very hard to regrow damaged root systems so, recovery potential for these plants isn’t very good.

Rhizoctonia Root Rot on Coreopsis

Many plants with poor growth this summer have been suffering due to saturated soils and high temperatures. However, sometimes plant decline is due to a disease. This Coreopsis bed sustained damage from a fungal disease called Rhizoctonia crown and root rot. The disease can survive in the soil for long periods and is triggered by high temperatures and moist soils. Long-term the best management option is to start over with new Coreopsis plants in a new location.

Turf disease update

Megan Kennelly, KSU Plant Pathology

Moisture and humidity are causing continued disease activity in both ornamentals and turf.

Below is some dollar spot activity in untreated controls in a fungicide study. As you can sort of tell from the photo, the disease has gotten to the point where the infection centers are not just off color but are also sunken/pitted.

If you are struggling with dollar spot control, consider your fertility regime. Low N can make the turf more susceptible, but high N comes with its own issues. Check your nozzles and spray equipment to ensure good coverage. Be sure to rotate among different modes of action. For more details check the dollar spot section starting on page 14 of THIS DOCUMENT.


We are getting some heat and humidity, and brown patch is becoming more active. Typically we think about brown patch as affecting tall fescue, perennial ryegrass, and our putting greens. However, this disease can affect bluegrass, too. This photo shows a sample from a Kentucky bluegrass fairway. You can see the fungal mycelium. With all the moisture, foliar Pythium also came to mind as a possibility, but in the microscope it was clearly the brown patch pathogen.

In the photo below, you can also discern that this is a heavy clay soil – see how shiny and glossy it looks. And, there is a thatch layer starting to build up, which can lead to its own set of problems. This site already has an aerification plan in place for fall.


The final disease I want to mention is Pythium root rot in putting greens.

Saturated soils alone can cause major decline in root systems. Unfortunately those same conditions can trigger Pythium root rot. The photos below illustrate typical symptoms I’ve seen recently, including several already this week:

When you pull up a turf core, the root system does not cling together well, and the whole core kind of lacks structure. If you wash them off, they are brown and mushy.

Canopy is thinned out and yellowing:

In the microscope the roots are dark, sloughing outer tissues, lacking root hairs, and have Pythium oospores present. (The physiological decline from wet soils alone can also cause browning, lack of root hairs, etc)

Here are a couple of resources about this disease:




Hosta…one of my favorite plants.

By: Judy O’Mara

Hosta is a standard go to plant for every shade garden. They are very hardy and have few problems and you can plunk them in the ground and come back 20 years later and they will still be going strong. They really do have few problems…and yet, they aren’t problem free. Here are two things that I’ve seen on hosta this spring.

Anthracnose on hosta will show up as brown scattered spots. The centers sometimes drop out creating a shot hole appearance. Like all fungal diseases, it has been favored by the wet conditions this spring.

The impact of anthracnose on the plant is cosmetic. The disease is fairly easily cleaned up by picking off the infected leaves.

Aside from rainy weather, prolonged leaf wetness from watering late in the day can also promote conditions that favor the disease. Switching to morning irrigation will allow the leaves to dry out quickly, which in turn reduces disease activity.

A bit more serious is Hosta virus X (aka HVX). This disease is sap transmitted. If you divide an infected plant and then use the same tools to divide a healthy plant, the virus can be spread to the new plant. Virus diseases tend to weaken the plant, so infected plants may end up smaller and less vigorous than healthy plants nearby. The best way to avoid the problem is to inspect hosta plants when purchasing them. If you discover a plant with Hosta virus X in your yard dig it up and discard it.

Hosta virus X is tricky to identify based on symptoms because it can look similar to normal hosta variegation. Confirmation of the disease is done in a lab with a serological test (ELISA). However… one symptom that I have seen consistently associated with Hosta virus X is called ‘ink vein bleeding’. This is where the veins of the leaf have the opposite color and appear to be bleeding like an ink blot.

                   Healthy Hosta                                       Hosta with HVX

Iowa State University has a great publication on Hosta Diseases and Pests.


Spring Leaf Drop – Sycamore Anthracnose

by Judy O’Mara

I walk past a big beautiful Sycamore tree on my way into work every day. I recently noticed leaves dropping to the ground. A close look at the defoliated leaves showed the characteristic symptoms for a fungal disease called sycamore anthracnose – brown lesions along the veins and on the petiole. Once the water conducting tissue in the veins is damaged, the leaf gets knocked off the tree. Also visible in the tree were also small, blighted shoots.

Sycamore anthracnose is a spring disease, meaning it is favored by cool (60-73F), wet conditions. With a prolonged spring weather pattern, the disease can sometimes look dramatic. In Kansas, chemical control of this disease isn’t necessary. With the move into warmer summer weather, sycamore anthracnose ceases activity and the tree pushes out a new flush of growth.

Why is that Redbud tree blooming along the trunk?

Cauliflory on Redbuds

by: Judy O’Mara

It was a beautiful year for flowering redbud trees this spring. The pink flowers seemed to go on and on. As in past years, the question arises as to why redbud trees flower on the trunk or on large branches. The question just popped into my email inbox this morning: Is it a disease? Like everyone else, I’ve always meant to look up this interesting phenomena.


According to Michael Dirr (Manual of Woody Landscape Plants) and the Virginia Native Plant Society (https://vnps.org/wildflowers-of-the-year/2013-woty-redbud/), it turns out that flowering on the trunk or limbs aka ‘cauliflory’ is a normal growth characteristic for redbud trees. Flowers are produced in pink nodal clusters that can develop on any part of the tree, from twigs to branches, as well as the main trunk (particularly on old trees).

So now we know.

Spring turf diseases

(Megan Kennelly, KSU Plant Pathology)

As we move through spring and launch towards summer, don’t forget some key disease resources.

Fungicide info is available here:


and here in a searchable online database:



Large patch in zoysiagrass

Large patch has definitely been active lately with the cool, wet weather.

This is an area that was previously inoculated for a study, so it’s a high-pressure location:

In the photo below, the clear area was treated with a fungicide (tebuconazole) in early September and again in early October:

Some light N may help the turf recover. Some prior KSU work with U of Missouri (click here for info) and additional follow-up work by U of Missouri demonstrated that light N (think 0.25-0.5 lb/1000) in spring will not enhance this disease.


Dollar spot



The photo above is a worst-case scenario of the heaviest disease anywhere at Rocky Ford. It is an untreated area of a Cato-Crenshaw stand, which is highly susceptible. Untreated areas of less-susceptible cultivars are looking clean for now. KSU is part of a recently-published study that looked at disease susceptibility of various cultivars across several states. You can find a short preview/summary here.

What are you seeing? Let us know.


Root rot

We have not received samples here of Pythium root rot, but there are reports from nearby. You can read about findings of Pythium root rot in Missouri from our colleague Dr. Miller here:


May Weekend Warrior Reminders

(By Jared Hoyle, KSU Turfgrass Research and Extension)

This time of year we can be caught of guard when it comes to maintaining our lawn.  Today we have some reminders about maintaining cool-season turfgrass for all you weekend warriors out there!

  • Reminder – Avoid frequent watering to reduce weeds germination and disease.
  • May is time for fertilizing cool-season turfgrass that is going to be irrigated. (See information below from Ward Upham.)
  • Mowing Tip – Only remove 1/3 of the leaf blade at a time and make sure you mow your lawn at the recommended mowing height. For more information on mowing your lawn – https://www.bookstore.ksre.ksu.edu/pubs/MF1155.pdf 
  • Mowing Tip #2 – Retuning your clippings to the lawn can return up to 25% of fertilizer nutrients that would be lost if clippings were to be removed. – https://www.bookstore.ksre.ksu.edu/pubs/MF2110.pdf

Fertilize Irrigated Cool-season Lawns in May By Ward Upham

May is an excellent time to fertilize cool-season lawns such as
tall fescue and Kentucky bluegrass if they will be irrigated throughout
the summer. Non-irrigated lawns often go through a period of summer
dormancy because of drought and do not need this fertilization.
May is a good time to fertilize because the springtime flush of
growth characteristic of these grasses has tapered off, so the
fertilizer you apply will be less likely to cause excessive shoot growth
than if you fertilized at a full rate in April. Slow-release nitrogen
sources are ideal. These nitrogen sources promote controlled growth,
which is desirable as the stressful summer weather approaches.
Relatively few fertilizers available to the homeowner supply ALL of the
nitrogen in the slowly available form. But one such product that is
widely available is Milorganite. Other such products available in the
retail market include cottonseed meal, alfalfa-based fertilizers, and
any other products derived from plants or animals. (Bloodmeal is an
exception, and contrary to popular belief, the nitrogen it supplies is
quickly available.) These products are all examples of natural organic
fertilizers. They typically contain less than 10 percent nitrogen by
weight, so compared to most synthetic fertilizers, more product must be
applied to get the same amount of nitrogen. Translation: they are more
expensive! Apply enough to give the lawn one pound of nitrogen per 1,000
square feet. For example, if the fertilizer is 6 percent nitrogen by
weight, you will need to apply almost 17 pounds of fertilizer product
per 1,000 square feet. Summer lawn fertilizers that contain at least a
portion of the nitrogen as slow-release are fine to use as well. Be sure
to follow label directions. If cost is prohibitive, you can use the less
expensive quick-release (i.e., soluble) sources, but split the
application into two doses as follows: apply enough to give the lawn 0.5
lb nitrogen per 1,000 square feet in May and again in early June.

***** Reminder –  These are recommendations for cool-season turfgrass species!*****

For more information on tall fescue lawns – https://www.bookstore.ksre.ksu.edu/Item.aspx?catId=545&pubId=1460

For more information on Kentucky bluegrass lawns – https://www.bookstore.ksre.ksu.edu/Item.aspx?catId=545&pubId=816 

Cedar apple rust

(Megan Kennelly, KSU Plant Pathology)

The birds are singing, the tulips are blooming, and junipers (also called red cedars) are “blooming” in another fashion.  Cedar apple rust is here.  The pathogen (a fungus) spends part of its life cycle on a juniper tree, and the other part of its life cycle on apples, crabapples, hawthorns, or quince.  To simplify, we’ll just call them “apple hosts.”

Those jelly-like orange masses on the junipers produce spores that infect the apple hosts.  Once infection occurs, leaf spots on apple leaves develop in 1-3 weeks.  Eventually, fungal spores are produced in these leaf spots on the apple tissues.  The spores are spread by wind and rain back to junipers starting in about July.  Without both hosts, the fungus can’t complete its life cycle.
The disease looks dramatic on junipers, but it does not cause any harm.  The rusts can cause problems in the apple host, however.  If infection is severe, many leaves drop off early and the tree is weakened due to reduced photosynthesis.   If your tree only gets a small amount of rust each year, it probably won’t be an issue for long term tree health.
Management options (for apple hosts):
1) Resistance:  For new plantings of fruiting or flowering apples, consider planting a rust-resistant variety.  Information on crabapple cultivars is available at:
2) Tree care:  For any apple tree, proper pruning will allow air movement through the canopy. This practice reduces the leaf wetness that promotes disease.  Maintaining overall tree health will also help prevent the disease.
3) Fungicides:  Homeowners with a bad history of this disease (severe defoliation), might consider preventative fungicide sprays on the apple hosts when leaves are out and the orange galls are active.  For best control, applications should continue through May or as long as the orange galls are active. Products with the active ingredients myclobutanil or propiconazole are examples of materials labeled for cedar apple rust management in flowering crabapples and non-fruiting apples.  Make sure you check the label carefully. For example, if you are talking about fruiting apples instead of flowering crabapples, some products are not allowed.

Commercial fruit growers should consult the Midwest Fruit Pest Management guide: https://ag.purdue.edu/hla/hort/documents/id-465.pdf

There is also a video on rust diseases at: https://www.youtube.com/watch?v=yQdwSPtvhH8  The video is 15 minutes long and describes the life cycle and biology of these fascinating fungi!

Paying Attention to Pine Diseases

Now is a really good time to check for Dothistroma Needle Blight on Austrian, Ponderosa and Mugo pine trees. Several pine samples from northeast Kansas have the K-State Plant Disease Diagnostic Lab with classic symptoms. This disease tends to show up in crowded, mature pine plantings. The key is crowded plantings that lead to poor air circulation. Wet weather and poor air circulation lead to increased disease severity.


If you are trying to sort out winter damage from Dothistroma needle blight, the first thing to do is to look into the bottom of the tree. Dothistroma causes needle shedding and tends to be more severe in the bottom of the tree. Essentially when you look into the bottom of the tree, the interior needles are gone and all of the lower limbs tend to be bare. Needle loss tends to be particularly severe in crowded windbreaks where air circulation is poor.

Next take a look at the foliage. The needles will have scattered spotting and a half needle scorch. The outer needle tip will be brown and the inner portion of the needle will be green. Each needle will be affected in a different location.

You can contrast this with winter burn which can also produce a half needle scorch but will always burn all of the needles back in exactly the same location. Plus the damage tends to be in the outermost foliage.

The last thing to look for is raised black fruiting bodies (acervuli) on the affected needles. This is diagnostic sign for the disease. You may need a magnifying glass or 10X hand lens to see them, although when they are fully mature they are visible with the naked eye. The fungal fruiting bodies don’t start developing until late December or January, but now is a good time to look for them. If you don’t initially see them you can put the suspect needles in a Ziploc bag with a wet paper towel for couple of days. The high humidity will help the fruiting bodies pop out.

Dothistroma needle blight and winter damage can look very similar. If you are going to spend money to treat for the Dothistroma needle blight disease then it is a good idea to confirm that the disease is present. Samples can also be sent to the K-State Plant Disease Diagnostic Lab at the address listed at the bottom of this post. Dothistroma needle blight can be managed with fungicides.

For more information on managing this problem see the pine disease factsheet at the following web link (O’Mara):


K-State Plant Disease Diagnostic Lab
4032 Throckmorton, PCS
1712 Claflin Rd
Manhattan, KS 66503
Send Questions to: jomara@ksu.edu
Testing for Needle Blight: $10 Extension/$13.50 Non-Extension

Cut and destroy those pine wilt infected trees ASAP

(Megan Kennelly, KSU Plant Pathology)

Pine wilt has been killing our pines for decades. It is caused by a nematode (microscopic worm) that is spread by a beetle. The nematodes and beetles spend the winter in dead and dying trees. The beetles, loaded up with nematodes, start emerging in late April or early May and spread to new trees. Got pine wilt? Get that tree outta there! Chop it down, and burn or chip the wood, making sure not to leave stumps. Get this done in early April to stop disease spread.

If you have a dead pine in the eastern 2/3 of Kansas it could very well be pine wilt. Sure, it could be something else, like drought, but if it’s dead anyway you might as well assume it is pine wilt, and get it out and destroyed. You can send a sample in to KSU for testing if you want to know.

And, if you suspect pine wilt in the western part of the state, contact your local county K-State Research and Extension agent for help. Not only do we want it destroyed, we want to know where it is so we can understand where disease is spreading. (Find your agent here: https://www.ksre.k-state.edu/about/stateandareamaps.html)


Entirely dead tree? Cut it down and destroy the wood by chipping or burning.




Pines have multiple problems though, such as tip blight and Dothistroma needle blight. If you have any doubt you can work with your KSRE Extension agent to ship a sample up to KSU. For more information on pine diseases, and how to tell them apart, check out our publication about Pine Diseases in Kansas