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K-State Turf and Landscape Blog

Category: Diseases

Nitrogen Rate and Fungicide Had Big Impact on Brown Patch in Tall Fescue this Summer

If you were at field day on August 3rd, you likely saw the experimental area that was highlighted by Dr. Megan Kennelly.  A turf-type tall fescue blend has been treated the past two years as either: High N level; or Low N level.  High level involved 4.5 lbs of N/1,000 ft2/yr  (Months applied listed in lbs N/1,000 ft2 – 1 in April; 1 in May; 1.5 in Sept.; 1 in Nov) and low N level was 1.5 lbs of N/1,000 ft2/yr (single application in September).  In addition, half of the plots receiving these treatments either received two fungicide applications from azoxystrobin (Heritage) each growing season or none.  You’ll see a photo below of how N impacted brown patch on tall fescue.  More details will come out in the 2024 K-State Turf Research Report.  Bottom line summaries:

  • High N levels provided high quality turf, but fungicide application was required to maintain it when brown patch infection began.  Turf receiving high N without fungicide declined quickly in quality starting in July.
  • Brown patch levels were comparable in July in turf receiving high N from standard urea, humic coated urea, or combinations of 50% slow release + 50% quick release N.
  • Low level N generally provided turf quality that was at or just below an acceptable level (but not high quality) and had little brown patch even when fungicides were not applied.

    Impact of N level on brown patch in tall fescue with no fungicide application.

Got Plant Questions? The K-State Plant Disease Diagnostic Lab Has Answers.

By Chandler Day, Associate Diagnostician, K-State Plant Disease Diagnostic Lab

 

 

A quality diagnoses starts with a quality sample. A sample can be physical plants or digital images of plants. Digital images are a great screening tool to determine if a physical sample is required for diagnoses. In order to make a diagnosis, the quality of the images and/or samples is extremely important. Follow these tips for submitting your plant health questions. If you ever have questions about a plant problem, how to collect and/or ship a sample, feel
free to call or email us.

Inform. Collect. Ship.

Inform:

Send photos and background information to clinic@ksu.edu!

Three types of high quality digital images are an excellent way to pre-screen plant health issues.

  1. Symptoms up close (Fig. 1)
  • Take zoomed in photos of the problem/symptoms.
  • Ensure the image is in focus by tapping the image before you take the shot.
  • Examples of symptoms: leaf spot, branch die-back, sunken tissue, scorched leaves.
Fig 1. Close-up and focused image of leaf spots on iris.

 

  1. Entire plant. (Fig. 2.)
  • Take photos of the entire plant that includes all plant parts from soil level to the top of the plant.
  • Ensure the symptoms are still visible in this type of image.
  • Example: whole tree or shrub (trunk/base to top of crown).

 

Fig. 2. Photo of entire Iris plant with leaf spot still visible.

 

  1. Landscape pattern. (Fig. 3.)
  • Stand back and capture the entire landscape where the plant resides.
  • Include in the photo the surrounding plants, concrete, rocks, drain spouts, or whatever else is near the symptomatic plant. Don’t worry if the symptoms cannot be seen in this type of image.
  • The importance of this image is not to capture the symptoms on the plant but to capture the landscape. This gives us look at how the affected plant is growing within the site and if there are any site issues that might be contributing to the problem.
Fig. 3. Overall landscape view of flowerbed with Iris plants.

 

Useful background information:

  1. Site history:
    • Soil types, drainage, slope, sunny or shady problem areas, previous construction activity, proximity to structures such as roads or sidewalks, etc.
  2. Irrigation practices:
    • Frequency of irrigation, length of time, irrigation application method (sprinkler, drip, hand held hose), time of day
  3. Chemical history:
    • Pesticide usage and timing, fertilizer applications, etc.
  4. Pattern on plant:
    • Describe the problem. Are symptoms on new or old growth? Top or bottom of plant?
  5. Pattern in landscape:
    • One host or multiple hosts? Other plants in the landscape showing similar symptoms?
  6. Timing:
    • When did the symptoms occur: All at once? (i.e. after a storm?) Slowly over time?

 

Collect:

  • Complete the sample submission form with as much information as possible.
  • Send a “healthy” plant and a “sick” plant.
  • Submit entire plants when possible including roots. (EX. Tomatoes, annuals, turf grass, etc.)
  • DIG up plants. Do NOT pull up plants as this can damage the roots.
  • Bag roots separately and then place entire plant into larger plastic bag.
  • Do NOT add water or use paper bags. These degrade the sample quality and affects the diagnostic process.
  • For specific collection guidelines, go to the K-State Plant Disease Diagnostic Lab webpage, scroll down to where it says collection tips, and use the arrows on the right hand side to navigate to the appropriate collection strategy.

 

Ship:

  • Collect and ship samples on the same day. If this is not possible, store plants in plastic bags in the refrigerator until shipping is possible.
  • Ship plants overnight using UPS or FedEx. UPS can take up to 14 days even with 2 day priority shipping.
  • Ship on or before Wednesday to avoid weekend storage.

 

The K-State Plant Disease Diagnostic Lab is here to help you identify your plant health problems. If you ever have questions about a plant problem, how to collect and/or ship a sample, feel free to call or email us.

 

K-State Plant Disease Diagnostic Lab
4032 Throckmorton PSC
1712 Claflin Road
Manhattan, KS 66506
clinic@ksu.edu
785-532-6176

 

Brown Patch on Tall Fescue

By Ward Upham and Jack Fry

We have been receiving numerous reports of brown patch showing up on tall fescue. This disease is favored by warm night temperatures and extended periods of leaf wetness. If you go outside in the morning and the lawn is covered with dew and the temperature is in the high 60’s or higher, it means that conditions are getting right for brown patch. The fungus is primarily a leaf pathogen and does not attack the roots. During severe outbreaks, the fungus may invade the lower leaf sheaths and crown and kill plants. But in most cases, the turfgrass can recover from brown patch. This recovery may take two to three weeks, depending on weather.

There is no way to eliminate brown patch from a lawn. It will persist indefinitely in the soil. Therefore, the disease is not carried from one lawn to another. In almost all cases, the limiting factor for brown patch development is the weather, not the amount of fungal inoculum. Although you can’t eliminate the fungus, cultural practices – especially irrigation – can help control it. Don’t water in the evening; instead, water early in the morning. This will help decrease the number of hours the leaf tissue remains wet and susceptible to infection. The frequency of irrigation is not as important as the time of day you do it. Don’t overfertilize and certainly don’t fertilize when brown patch is active. Also, don’t allow your seeding or overseeding rates to become too high.

Fungicide applications should begin in mid-June and continue through August. Often tall fescue lawns will recover from brown patch but infections this year seem more severe than usual and may require overseeding this fall. CLICK HERE to find the useful source for fungicides effective on brown patch.

Fungicide guide and dollar spot resource

Megan Kennelly, KSU Plant Pathology

It is June 8 and summer is in full swing.

Fungicide resource:

I wanted to remind everyone of this excellent commercial guide to fungicides:

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

It is developed by University of Kentucky, University of Wisconsin, and Rutgers University. It is based on research and reports by universities all across the country. I mention it every year and at every turf conference. It is definitely worth downloading, bookmarking, and/or printing out.

 

Dollar spot forecasting resource:

The Smith-Kerns dollar spot forecasting model is available online here:

https://www.greencastonline.com/dollar-spot-solutions

You can type in your zip code and see daily disease risk assessments, based on weather conditions. It uses 5-day rolling averages of temperature and humidity to designate a risk factor. (If you want more details on how it was developed and how it works check out this article.)

Here at KSU we are doing a trial this year looking at this forecasting model as part of a multistate project led by Wisconsin. Several states are working together to examine how the model performs in varieties of bentgrass with different inherent susceptibility levels. Stay tuned for research reports in the future.

Hot/humid = brown patch season

Megan Kennelly, K-State Dept of Plant Pathology

 

Hello everyone,

Some of our mornings have had that “tropical” feeling lately! We are getting some reports of brown patch activity in tall fescue. So far it’s more from the eastern side of the state which of course does have more moisture.

Brown patch is favored by humid weather with nighttime lows around 70 degrees or above. It can occur when the nighttime lows are above 60 though.

The disease can have distinct patches OR be “diffuse/blotch” as shown in these photos:

Patchy

 

 

 

That is a little confusing, right? Tall fescue can also suffer from drought, grubs, general stress, etc. So – how do you tell if it is brown patch? Take a close look at the leaf blades as shown in the photos below. First, you’ll notice that tall fescue has a lot of prominent veins with a rough texture. That is ONE way to help tell it is tall fescue and not something else.

For brown patch look for a tan spot, irregular shape, with darker brown border:

Finally, if it is very moist/dewy you might see some cobwebby fungal growth – look closely here. That dries up very fast once the sun hits and the turf dries off, though.

 

To help prevent the disease you can make the site less favorable:

  • avoid irrigating in the late afternoon/evening to prevent long periods of leaf wetness
  • improve airflow
  • avoid excess fertilizer

There are a lot of fungicides labeled for brown patch. Here is a great guide for commercial lawn care:

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

Brown patch is on page 12, and I will not repeat all those details here. You can click and get a ton of helpful tips right there. Keep in mind that as with most diseases preventative applications work better than after the disease has kicked in. Also – turf fungicides don’t magically turn the turf healthy again. New, green grass needs to GROW and when we hit full summer stress that is slow to happen.

Finally, if you need help with a turf diagnosis you can email me (kennelly@ksu.edu) and/or send a sample to me here at KSU via the Plant Diagnostic Clinic.

Quick tips on a good sample:

Field Day Videos on Pest Management – See these Speakers at Conference!

Here are video recordings of field day presentations (last August) of a few speakers you’ll hear at the Kansas Turf and Landscape Conference, which is in Manhattan, KS on December 1 and 2.  You can’t get pesticide recertification credit by watching the videos below, but you can if you come to the conference (7 cr. of 3A and 3B will be available!).

 

Field Day recordings – Click on the name to see it!

Dr. Raymond Cloyd – Insect Update

Dr. Megan Kennelly – Disease Update

Dani McFadden – Weed Update

Sessions at the upcoming conference include Basic Turf; Nursery & Landscape; Diseases, Insects & Weeds; Advanced Turf; and Sustainability, Technology & Water Management. You can download the conference brochure and get exhibitor information by CLICKING HERE!

Complete online registration by CLICKING HERE!

 

 

Nonchemical Weed Control Methods for Landscape Beds

By Dr. Cheryl Boyer

Dr. Chris Marble at the University of Florida is a weed management whiz. He’s a machine with research and writing and a kind friend and teammate of mine from graduate school at Auburn University. Naturally, I’m pretty excited and proud to see a paper he has authored published. I’m going to kick off my series of posts for the K-State Turf and Landscape Blog by reviewing some of his journal articles with clarity on which practices apply to Kansas and which may not (since they have a few different weeds in Florida).

First up is the first in a two-part review of weed control practices for landscape planting beds. We all know that fighting weeds is a significant part of work in both landscape and turf worlds. Chemicals vary for both of those applications, and we’ll get into that next time. For now, nonchemical weed control is where we’ll start. What comes to mind? If you’re thinking mulching and hand weeding, you’d be right. However, some best practices may impact other weed management choices and hopefully result in reduced herbicide application.

Types of nonchemical weed control:

Type Example Pros Cons
Mechanical disruption Mowing, hand-pulling, hoeing, tilling Depending on the application, it may be the most aesthetically pleasing approach. Time-consuming, labor-intensive, disrupts soil structure, may propagate weeds.
Physical barriers Geotextiles, landscape films, or fabrics In combination with mulch, it can be very effective Reapplication required, material may be destroyed by weeds growing on top of the fabric, does not contribute to soil health, in Kansas wind can be problematic
Cultural control Mulching, plant selection, fertilization and irrigation placement, thermal treatment Great for soil health (organic mulches), aesthetically pleasing, reasonable weed control when applied at least 3-inches deep Mulch type matters, reapplication, and scouting required, inorganic mulches do not contribute to soil health, and rubber mulch leaches zinc and other heavy metals into the soil.

 

Mulching is the A-#1 best choice for nonchemical weed control the average landscape bed. However, material selection is essential. For organic mulches, stick with large chunky (coarse) pine bark or pine needles and apply it at least 3-inches deep. Hardwood bark can be acceptable, but some species (and it’s not always easy to know which species is in the product you’re purchasing) have allelopathic chemicals which could damage ornamental plants. Fine-textured materials like compost and screened bark may encourage weed growth, so avoid those materials or refuse to accept a bark load that is too fine if you plan to use it for landscape mulch. These materials do break down over time which is good for soil health but requires reapplication.

Inorganic mulches are not ideal. They’re expensive, generally heavy, difficult to apply (and challenging to remove), and do not break down over time to contribute to soil health. Rock mulches, in particular, may bounce heat back up into the canopy of ornamental plantings, contributing to plant decline. Rubber mulches leach zinc and other heavy metals into the soil, which can also harm plants. I do not recommend inorganic mulches.

Now let’s address landscape fabric, geotextiles, etc. I don’t recommend plastic material because research has documented that water, air, and nutrients can’t get down to the soil, so ornamental plants don’t have access to the elements of life. While landscape fabric can be adequately effective, it is not usually so because weeds grow on top and through if not appropriately managed. Mulch cannot degrade into the soil (enhancing soil health and facilitating the mulch material staying in place). That’s an important point in Kansas, where the wind often whips loose mulch away from planting beds, particularly if landscape fabric is applied underneath. At that point, the landscape fabric is often unsightly, flapping in the wind with no mulch to hold it down (unless the “mulch” is rock). Landscape fabric is only effective for a short period of time and does not control perennial weeds. There may be some applications where landscape fabrics make sense, but I don’t recommend it in general.

Plant selection: we’re talking about perennial groundcovers now. If they grow densely enough and don’t die back to the ground during the winter, they may shade out some weeds. Of the studies mentioned in Dr. Marble’s review article, the ones that grow well in Kansas include:

  • Lady’s mantle (Alchemilla mollis): 1 to 1.5 feet tall, 1.5 to 2.5 feet wide, June bloomer, full sun to part shade (can handle almost full shade, particularly in the afternoon), tolerates rabbit and deer. May be an aggressive self-seeder, remove spent flowers to avoid spreading too much.
  • Catmint (Nepeta xfaassenii): 1 to 2 feet tall, 1.5 to 3 feet wide, blooms all summer, full sun to part shade, tolerates deer, dry soil, and shallow, rocky soil. Sterile.
  • Moss phlox (Phlox subulata): up to 0.5 feet tall, 1 to 2 feet wide, flowers March to May, full sun, attracts butterflies, tolerates deer, drought, erosion. Need good drainage.
  • Goldenrod (Solidago sphacelata): 1 to 1.5 feet tall and wide, flowers in the fall, attracts butterflies, tolerates deer, drought, erosion, clay soil, dry soil, and shallow-rocky soil. Can colonize through rhizomes and self-seeding (needs deadheading to manage).
  • Sheep’s burr (Acaena inermis ‘Purpurea’): 1 to 2 feet wide, 1.5 to 3 feet wide, blooms June to August, prefers full sun and dry soil (low maintenance), tolerates deer, drought, and shallow-rocky soil.

Of course, we have to think carefully about using plant choice as a nonchemical weed suppression tool because some plants can become invasive (Liriope spicata, for example). Be aware of the Kansas noxious and invasive weed lists; you can find them here: https://agriculture.ks.gov/divisions-programs/plant-protect-weed-control/noxious-weed-control-program. Side note: did you know we have Kudzu in Kansas? It’s true, sadly. Kudzu is an interesting plant, but that is a story for another day.

Hand weeding and cultivation are always an option, although labor-intensive (and thus costly). Without other control measures, weeds will likely pop up again quickly.

Here’s a fun one: Thermal weed control. That’s right, steam, hot water, flame from a propane burner, or solarization. Thermal weed control has limited applications because you need to be careful about the areas around where you use the tool. Ideally, the use of these tools will be centered on hardscapes and other non-planted areas to eliminate large perennial and grass weeds. Solarization is a long-term process where plastic is used to cover areas for an extended amount of time to kill weeds and weed seeds. It requires reapplication and could damage nearby ornamentals or other tools like hoses or irrigation heads. These are likely not your best choices for nonchemical weed control and additionally can be dangerous. Use these as a last resort, get training, read manuals, and BE CAREFUL!

Lastly, consider fertilizer and irrigation placement. In container-grown nursery crop settings, weed pressure can be reduced when fertilizer is dibbled or banded within the container substrate profile. Fertilizer placement makes a lot of sense because if Nitrogen is easy to access, weeds will go to town (and your ornamentals may starve). Interestingly, sub-irrigation in container studies can be adequate for weed control. However, studies of sub-irrigation in landscape beds have proven it to be an ineffective practice for managing weeds.

These choices depend a great deal on the project, application, and client tolerance for weeds. The best approach is likely to apply various weed control methods, which may include chemical controls for the longest-lasting effect. We’ll cover those next time.

Marble, S.C., A.K. Koeser, and G. Hasing. 2015. A review of weed control practices in landscape planting beds: Part I—Nonchemical weed control methods. HortScience 50(6):851-856. https://doi.org/10.21273/HORTSCI.50.6.851

Extension Publication Update

By Brooke Garcia

There is a new publications of interest recently updated through K-State Research and Extension by Dr. Raymond Cloyd:

Magnolia scale, Neolecanium cornuparvum, is an insect pest of magnolia trees including star magnolia, Magnolia stellata, and saucer magnolia, Magnolia x soulangiana. Magnolia scale is native to the U.S. and is the largest soft scale in North America. This publication discusses the biology, damage, and management strategies that can be used to avoid plant damage caused by magnolia scale.”

Read more here: Magnolia Scale: Insect Pest of Magnolia Trees. MF3560. Raymond Cloyd.

Photo Credit: William Fountain, University of Kentucky, Bugwood.org

Root decline, Pythium root rot, and anthracnose in recent samples

(Megan Kennelly, KSU Plant Pathology)

Here is a sample that came into the lab recently:

You can see turf decline, and if you look closely you can see some dark green algae in the brown area. Algae often indicates poor drainage. This site is in a low area with poor airflow. The site has a lot of underlying stress.

Here is a view of the washed-off roots sitting on the dissecting microscope. They should be a creamy white but instead they are more of a brown color. They were mushy in texture as well.

 

Finally below is a closer view in the compound microscope. You can see how the roots are dark. Healthy roots are much more clear/transparent. These are also lacking fine root hairs, and the outer tissues have sloughed off.

These symptoms occur frequently in sites with poor drainage. The roots sit wet, and oxygen flow is disrupted. The wet soil holds heat overnight as well.

The environmental stress alone can cause major root decline and turf damage.

In addition, these conditions can trigger Pythium root rot. (This particular sample did have some Pythium as well, I just had a hard time getting a clear photo). And, these stress conditions can also lead to crown anthracnose. I’ve seen a couple of samples with that disease lately as well. Anthracnose is more likely to chow down on turf that is already stressed.

Here is a link to a publication I’ve mentioned countless times on this blog:

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

There are excellent sections on individual diseases, but there is also a detailed section about summer stress on page 6. Many of the stress-reducing practices listed there will also reduce susceptibility to diseases.

That publication does not discuss Pythium root rot (PRR). (It does discuss Pythium root dysfunction (PRD) which is related but different.) Here is a great resources on PRR:

https://www.turffiles.ncsu.edu/diseases-in-turf/pythium-root-rot-in-turf/

Each year, we say, “I hope this August isn’t a bad one”. This coming week there will be some lower highs (low to mid 80’s) and “lower lows” (mid-60’s overnight, and even some upper 50’s! Woohoo!). Cool temps will be a blessing. However, continued rain may exacerbate drainage problems.

Managing the diseases is important, but it’s critical to address the physiological/environmental stresses as well or the turf can still suffer major decline this time of year.

 

 

Tips for submitting a ‘digital sample’ to plant disease diagnostic lab

By Lucky Mehra

When it comes to plant health, physical samples are best. However, sometimes it is not practical to send physical samples, such as with large trees or shrubs. A digital sample can be a good alternative or a good first step. By ‘digital sample’ we mean submitting digital images of the plant problem to the KSU plant disease diagnostic clinic.

Consider the following tips to take the photos and provide all the relevant information to help us diagnose the problem quickly and correctly.

Pictures

The main component of a ‘digital sample’ is the set of digital images itself. Take the following types of pictures to help us understand both the ‘big’ and ‘small’ picture of the problem. Make sure that the plant or plant part is in focus when taking pictures. Some phones are pretty good at auto focus, but most of the time you will need to tap on the screen at the point of interest to guide your camera to focus at a particular point.

  • Take pictures from a distance to give us the landscape view or the ‘big picture view’. It should include the whole tree/shrub along with neighboring plants (Fig. 1).

Fig. 1. The Hawthorn tree in the foreground has leaf spots. This image is to give an overall view of the landscape. For example, proximity of the tree to the concrete and adjoining trees.

  • Photo of the affected plant(s) i.e. the plant(s) showing the problem.
  • Photo of the affected plant part, whether it is leaf, flower, stem, twig, or root (FIg. 2).

Fig. 2. Affected leaves of the hawthorn tree.

  • Try to take a close-up shot of the problem symptoms (Fig. 3). If there are signs (actual parts of the pathogen i.e. fungal mycelium or other structures) present on the plant part, try to zoom in, tap to focus, and then take the photo. Take multiple photos to ensure that you will have at least a few good quality ones. If you have access to a microscope, you can bring the affected plant part to your home or office and focus it under the microscope. With some patience, you can also take really good macro shots with your phone through the eyepiece lens. Many of our students take photos this way in the lab. 

Fig. 3. An example of close-up images of a hawthorn leaf (top side of leaf on the left, and underside of leaf on the right) with yellow spots taken with a phone camera, without any additional lens attachment.

Additional essential information

Sometimes, the plant problem is very peculiar, and it is easy to identify by just looking at the photos you submit (e.g. yellow spots on hawthorn leaves shown above are the symptoms of Cedar-hawthorn rust); however, most of the time it is not possible to diagnose a problem only based on photos. We need much more information from you to help us with the correct diagnosis. Provide as much information as you can. Please see below for the type of information that will be useful to us when making the diagnosis.

Site history and pattern

Make sure to provide information about the site where the shrub or tree is located. That information may include soil type if known, soil pH, slope, distance to the concrete sidewalk or road etc. 

Are there any drainage problems? Is this the only plant affected? Are other plants of the same species affected? If yes, what is the pattern of these plants in the landscape i.e. is there a cluster of affected plants or the distribution is random? Are other plant species affected?

Plant pattern

Tell us about the affected plant part whether it is leaf, stem, flower, twig, stem or root. Additionally, report the location of symptoms on the plant. Some problems tend to occur on younger leaves, others are specific to older leaves. All this information can help us rule out some issues and narrow down the diagnosis.

Timing of the symptom appearance.

Was there any weather event such as temperature (too hot or too cold) or moisture extremes (e.g. heavy rainfall) prior to the symptom development. We can download these data from a local weather station as well, however, rainfall events can be non-uniform over the whole area covered by a weather station. So if you have onsite information about the weather data, report it to us.

Chemical history

Any history of chemical or fertilizer application should be provided. This can help the diagnostician in figuring out if the problem is arising due to chemical exposure or due to a biotic agent.