Plant Diseases

Identifying and Treating Winter Kill in Turf

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Clint Waltz, UGA Extension Turf Specialist

Image - Winter kill in centipede taken from presentation by Clint Waltz, UGA Turfgrass Specialist
Image – Winter kill in centipede taken from presentation by Clint Waltz, UGA Turfgrass Specialist

We’ve received many questions regarding grass that has failed to green-up this spring.  With variations among four different warm-season species, multiple climatic conditions, and because of the wet conditions leading to a likelihood of disease, there is much to be said on the topic of “winter kill”.   In many incidents there are circumstances and extenuating factors that make a specific diagnosis difficult. If there were a year for winter kill, after the cold conditions this past winter and early spring, this would be the year for it.

Click here for a brief presentation about Winter Kill.

Dr. James McCurdy at Mississippi State has written a good blog on winter kill in his state, and over the past 30 to 45 days I’ve seen many of the same issues in Georgia so my comments would be consistent with his.

  • In many cases, bermudagrass has greened-up and is beginning to grow.  I’ve seen a few lawns and pictures of some bermudagrass that is still brown.  Patience may be the key with bermudagrass.  Soil temperatures have only been conducive for growth for about two weeks.  Remember bermudagrass has rhizomes, below ground stems, that were likely well insulated by soil.  Warmer temperatures and time will likely be suitable for bermudagrass recovery.  Check for extenuating factors like shade and ask questions about how long ice or snow remained on the lawn / grass.  I have seen some incidences where sledding occurred and the brown tracks are consistent with the path of wintertime fun.
  • Hybrid bermudagrass have recovered better than common-type (i.e. seeded) bermudagrasses.  The commons are recovering – all be it slowly.
  • Zoysiagrass have fared well but are slow to resume active growth.  See my comments for bermudagrass regarding soil temperatures and patience.  Remember, zoysiagrass is inherently a slow growing species, so recovery is going to take time.  It too has rhizomes and with time will regenerate itself as environmental conditions become favorable for growth.  To help, vertical mowing (i.e. verticutting) can aid in getting light and warmth to the soil surface.  This cultural practice can help remove dead leaf material and speed recovery.
  • Centipedegrass and St. Augustinegrass have suffered the greatest.  There are many cases where reestablishment is going to the best option.  Consider making the decision early (i.e. now) and getting started with sodding or seeding as soon as possible (see slides)
  • Grass that was sodded last year is a hit or miss. Some bermudagrass and zoysiagrass that is less than a year old seems to greening-up and doing fine. Some is not. This is more likely a result of post establishment care, position within the landscape, and how late into the summer or fall the grass was sodded. Grasses planted earlier in the summer seem to be doing better than those established later. That stands to reason as the earlier planted grass had more time to establish and produce rhizomes and roots before the onset of winter. However, I’ve seen some zoysiagrass sodded earlier in the summer, on a northern exposure that didn’t make it through the winter. Water wasn’t an issue most of 2013, third wettest year on record. As a result, the associated lack of ample sunshine during the 2013 growing season may have contributed to suboptimal establishment and production of carbohydrates – a biochemical molecule responsible for energy and energy storage. With compromised production of carbohydrates, the turfgrass plant had less stored energy to initiate growth (i.e. green-up) this spring.
  • Fortunately I have not seen many incidences where I think early spring fertilization is the primary culprit for “winter kill”. But I have spoken with a few homeowners and landscapers that applied nitrogen in late February and early March, before soil temperatures were conducive for warm-season root growth (65ᵒ F). One was a centipedegrass lawn where the early fertilization coupled with the “Easter freeze” likely affected the majority of the lawn. From what I’ve observed to this point, I think the early fertilization is more closely linked to increased occurrence of disease (e.g. large patch) which is making homeowners think their lawn was affected by the low temperatures. Regardless of year, this issue is self-imposed and 100% avoidable.
  • In my plots the three primary St. Augustinegrass cultivars grown in Georgia (i.e. Mercedes, Palmetto, and Raleigh) have had some degree of damage.  The difficulty with St. Augustinegrass is that in sod production it typically does not “lift” well during the spring, do it’s early summer before producers can provide a quality product.  If a homeowner is considering re-sodding St. Augustinegrass, they can start site prep now but be prepared that quality sod may not be available until mid-June.
  • Typically I don’t consider environmental injury as a primary culprit to turfgrass loss, but after last summer and this past winter it’s real this year, especially for centipedegrass.  I’ve seen several centipedegrass, and St. Augustinegrass lawns, that will likely need complete re-grassing.  There is little that can be done to recover these lawns in a timely manner and “sanding” will likely be of little help.  TifBlair does have improved cold hardiness relative to common centipedegrass but this year I’ve seen it injured too but that seems specific to areas that remained under ice or snow for several days.  TifBlair in more open areas where the sun shortened the duration of snow cover seems to be delayed but greening.
  • If reestablishment either from sod or by seed is desired – now is an appropriate time for either practice.  In fact, if seeding is chosen – the earlier the better.  If the lawn was healthy going into the fall, seeding may be the better option.  The homeowner can mow the existing lawn low (i.e. scalp), collect the biomass (i.e. clippings), opening the canopy for seeds to make soil-to-seed contact.  By keeping some of the existing grass it may help speed recovery and provides a medium for seed to become established (i.e. a nurse grass).  The caveat to this is there was no preemergence herbicide applied this winter or spring.  If so, then don’t seed.  The herbicide will kill the germinating centipedegrass seed too.  Lastly, follow watering and establishment practices for a newly planted lawn.

Successful seasonal color beds

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Planning before planting seasonal color beds can improve their impact & quality and reduce the potential for problems. This is a list of some UGA publications that may be helpful in planning and planting successful color beds.

Crop Rotation and Cultural Practices Help Reduce Diseases in Seasonal Color Beds by Bodie Pennisi, Department of Horticulture and Jean Woodward, Department of Plant Pathology

This publication explains how to effectively use crop rotation and cultural practices to reduce disease incidence in seasonal color beds.

Success with Herbaceous Perennials by Bodie Pennisi, Paul Thomas and Sheri Dorn – Department of Horticulture.

This publication is intended to provide the basics of perennial plant biology, ideas on design and installation, and information on cultivation and maintenance of perennial beds.

Color wheelColor Theory by Matthew Chappell1, Brad Davis2, Bodie Pennisi1 and Merritt Sullivan3  – 1 Department of Horticulture, 2 Department of Landscape Architecture, 3 Dept of Horticulture B.S. Student.

This publication explores color relationships in the landscape, ways of seeing plants in terms of color, and various ways to use color successfully in plant selection and landscape design and composition.

To find other helpful UGA publications, visit http://www.caes.uga.edu/publications/

New fungicides for ornamental disease control

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Jean Williams-Woodward, UGA Extension Plant Pathologist

Several fungicides for ornamental production have come on the market within the past couple of years. Below is a summary of some of the products.

Many of the products control Oomycete diseases including downy mildews and Pythium and Phytophthora root rot and blights. This is great news since there were few good Oomycete fungicide options available previously other than Subdue MAXX, Aliette and the numerous phosphonates/phosphites. Oomycete pathogens develop fungicide resistance readily.

Current research on Phytophthora and Pythium populations within GA nurseries and greenhouses has shown that approximately 5-25% of the isolates from individual production facilities are resistance to mefenoxam (Subdue MAXX). To reduce fungicide resistance development, always use products according to label rates and restrictions and rotate applications with products with a different mode of action (i.e. different FRAC numerical code).

Brand Name Active Ingredient FRAC # Sites1 Diseases Controlled
Adorn Fluopicolide 43 G, L, N Downy mildew, Phytophthora, Pythium: Must be tank mixed with a product with a different mode of action (different FRAC #) for fungicide resistance management
Disarm O Fluoxastrobin 11 G, N Broad spectrum – Rhizoctonia, Phytophthora, downy mildew, powdery mildew, anthracnose, leaf rusts, various fungal leaf spots and blights
Micora Mandipropamid 40 G, N Downy mildew and Phytophthora foliar blight and root rot: Provides a good rotation partner to Subdue MAXX, Segway and Adorn.
Orvego Ametoctradin + dimethomorph 45 + 40 G, N Downy mildew and Phytophthora: Contains the same active ingredient as Stature fungicide. Use in rotation with products with different mode of action.
Pageant Boscalid + Pyraclostrobin 7 + 11 G, L, N Broad spectrum – Anthracnose, powdery mildew, various fungal leaf spots, Botrytis, downy mildew, Phytophthora, Rhizoctonia, Cylindrocladium
Palladium Cyprodinil + Fludioxonil 9 + 12 G,L, N Provides good Botrytis control, plus other diseases including Rhizoctonia, powdery mildew, Cylindrocladium, Sclerotinia, Sclerotium rolfsii, Fusarium, certain fungal leaf spots
Segway Cyazofamid 21 G, L, N Downy mildew, Phytophthora, Pythium.
Torque Tebuconazole 3 G, L, N DMI fungicide with same mode of action as Strike, Banner MAXX, and Systhane. Controls powdery mildew, rusts, Sclerotium rolfsii, black spot, and various other fungal leaf spot diseases.
Tourney Metconazole 3 L, N For use on woody ornamentals (not floriculture). DMI fungicide. Controls anthracnose, powdery mildew, rusts.
Trinity TR Triticonazole 3 G, L, N Supplemental labeling for use on ornamentals. DMI fungicide. Controls anthracnose, powdery mildew, Fusarium, Rhizoctonia, Sclerotium rolfsii, Sclerotinia, certain fungal leaf spots
Veranda O, Affirm Polyoxin D 19 G, N Botrytis, Colletotrichum, Alternaria, Fusarium, Rhizoctonia, Sclerotinia

1  Location where product is registered for use: Greenhouse (G), Landscape (L), Nursery (N)

UGA mobile apps help professionals care for lawns

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Sharon Dowdy, News Editor with the UGA College of Agricultural and Environmental Sciences

Four mobile applications designed by University of Georgia specialists are putting lawncare information at your fingertips, literally.

The turfgrass apps created by UGA College of Agricultural and Environmental Sciences faculty make turf management in Georgia readily available. Turfgrass Management, Turf Management Calculator, Turfgrass Weeds and Turf Management Quiz can all be downloaded from the UGA Turfgrass Team website at www.GeorgiaTurf.com or straight to a mobile device through iTunes.

A lite version

The most popular UGA turfgrass app is Turf Management Lite. This free app was created with students, homeowners and professionals in mind. It includes photos of turfgrass varieties, pests, weeds and diseases.

Mobile applications, or apps as they are commonly called, can be downloaded onto smart phones like Droids and iPhones as well as portable tablets like iPads.

“Back in 2009, mobile apps were fairly new to smart phones. We saw a great opportunity to put the information where it can be easily accessed by mobile phone, iPods and tablets, instead of publishing a telephone-book-sized publication,” said Patrick McCullough, a UGA turfgrass specialist based on the Griffin campus. The turfgrass apps are his brainchild.

“Rather than have to go to the office and get an Extension publication or go online to view a publication, turfgrass professionals can now access the information they need in the field,” he said.

In-depth subscription version

There are three versions of the first app: Turf Management Lite, Turf Management Subscription and Turfgrass Management – Spanish. The lite and Spanish versions are free, but the subscription version costs $20 per year.

The subscription version includes everything from the lite version, plus information on pest control applications and a pesticide database. “You can search for trade names as well, and it includes PowerPoint presentations from UGA turfgrass faculty,” McCullough said.

The Spanish version is very popular in the turfgrass industry. “We have folks in the industry that speak Spanish as their first language. This app is a nice opportunity for those who are fluent in Spanish or primarily communicate in Spanish at work to have research-based turfgrass advice,” he said.

The Spanish version has been downloaded in more than 40 countries across the globe.

Making calculations easy

In 2011, the Turfgrass Management Calculator app was released. “It’s a comprehensive program that covers all types of applications, pesticide rates, fertilizer requirements, topdressing sand requirements, and calibration of sprayers and spreaders. Users enter known values of equations – like how much area is needed for a pesticide treatment at a certain rate. The app then does the calculation for you,” McCullough said.

College students majoring in turfgrass management use the app to double-check their math when learning these calculations, he said. “Some of these are very complex formulas. You can enter information for two products with different application rates and see which is more cost effective.”

The calculator app costs $5 and includes more than 16,000 pre-programmed calculations. It can also convert units from standard to metric. “It’s really a great tool for turfgrass managers and professionals, but students can learn a lot from it, too,” McCullough said.

Flash cards and quizzes

The Turfgrass Weeds app was released in 2011. It is designed to help users learn turfgrasses and weeds through a series of flash cards. “The cards reshuffle so users can continue to study and learn turfgrass species and weeds,” he said.

Just a few months ago, the UGA Turfgrass Team released its latest turfgrass app – Turfgrass Management Quiz.

“This app is a trivia style education game. You get test questions or photos with four choices to answer. You tap the correct answer, and when you’re done, you get a quiz score,” McCullough said.

The quiz app has two modes – quiz mode and study mode. Quiz mode scores your answers and study mode helps you get the correct answer.

“This app is perfect for students, but it can also be used by any turfgrass professional who wants to brush up on their knowledge. It’s a fun application that challenges you to get the best score, improve on your score and test your knowledge,” he said.

The new turfgrass apps are perfect for those who like to learn on their phones or mobile devices. UGA publications are also available online for computer users and in print form for those who still like the feel of a book in their hands.

“(Mobile apps) are a new technology – a new method to get information in the hands of the end user. We are trying to make it easier for people to get UGA turfgrass recommendations so it just makes sense for us to create these programs,” McCullough said.

To download the UGA turfgrass mobile apps or get more information on the turfgrass research at UGA, see the website www.GeorgiaTurf.com.

Boxwood blight update

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Jean Williams-Woodward, UGA Extension Plant Pathologist

Boxwood Blight is caused by the fungus, Cylindrocladium pseudonaviculatum, which causes leaf spotting, stem dieback, and death of almost all cultivars and species of boxwood. The disease moves quickly through infected plants, gardens, and nurseries.

It has been identified in 12 states (CT, DE, MA, MD, NC, NJ, NY, OH, OR, PA, RI, VA) and three Canadian provinces, and it is causing significant damage to boxwoods in those states, some in landscapes while others are restricted to nurseries. The pathogen also infects pachysandra (ground spurge) and causes similar leaf spots and stem dieback.

To date, Boxwood Blight has not been found in Georgia. However, introductions are possible on infected plants or on boxwood tip cuttings originating from out-of-state nurseries and suppliers.

Tan, circular leaf spots with a dark brown border develop within two days of inoculation. This is followed rapidly by the entire leaf turning brown, black lesions developing on the stems, and plant defoliation (see images). In some cases, time between leaf spot symptoms to plant death was two weeks.

This is a very damaging disease that you do not want in your nursery or landscape. The fungus produces white tufts of spores on the leaves and stems. The spores are very sticky and they will stick to pruning or digging tools, worker’s pants and hands, and dogs or other animals that may walk next to infected plants. In NC, wild turkeys were suspected of spreading the disease within field-grown boxwoods.

There is no control for this disease once it is present. The only control is preventing its introduction and preventive fungicide applications to protect non-infected plants.

Cylindrocladium diseases are difficult to manage with fungicides. Dr. Kelly Ivors at NCSU has conducted some fungicide trials against boxwood blight and has found that fungicides containing chlorothalonil (Daconil, Spectro, Disarm C, Concert II), fludioxonil (Medallion, Palladium) or tebuconazole (Torque) provided the best control when applied preventively. However, most of these products are either not labeled for control of Cylindrocladium or for use on boxwood or both. Pageant (pyraclostrobin and boscalid) is labeled for both boxwood and Cylindrocladium disease and provided fair to good preventive control. There is a great need for fungicide labeling changes and additions for this disease. Currently, fungicides are only needed in high risk areas where Boxwood Blight is known to occur. Spraying plants after the disease is present will NOT control this disease. Curative applications are ineffective.

If the disease is detected, the infected plants and all of its fallen leaf debris needs to be bagged on-site and removed from the area to be burned or buried to prevent its spread. In nurseries, propane torches have been used to burn any remaining leaf debris to rid the area of the pathogen; however, this may not completely control this disease.

The fungus also produces microscelrotia within roots and leaf debris of infected plants. Microsclerotia may allow the pathogen to remain viable at the site for years. Not to sound like an alarmist (but I have to here!), if I was in charge of a boxwood planting (box garden, topiary garden, historic plantation garden, nursery production, etc.), I would not bring in any boxwoods from anywhere. I would do all propagation in-house. You may think you are buying plants originating from a “safe” nursery, but in reality it could be a brokered plant that originated from an area where boxwood blight is present.

I also would not allow anyone to prune, shear, take tip cuttings, or touch my boxwoods if they have worked on boxwood somewhere else previously without first disinfecting their tools and changing their clothes. I’d rather make someone angry today, then for me to cry later because all my boxwoods are dead. Bottom line: You won’t get this disease if you don’t bring in any boxwoods. The spores are not wind-borne; they are water-splashed and carried on plants, people, tools, and animals. If you do bring in boxwood plants, make sure they come from a nursery certified to be free of Boxwood Blight.

Dr. Ivors has also conducted a Buxus cultivar susceptibility trial. Buxus sempervirens cultivars (English, American, Justin Brouwers, etc.) tend to be more susceptible. Buxus microphylla cultivars tend to be more tolerant of the disease; however, all cultivars can be infected. In fact, more tolerant cultivars could look asymptomatic, yet carry the pathogen (i.e. be a ‘ Typhoid Mary’), and spread the disease to surrounding susceptible plants. The value of cultivar susceptibility testing is in the establishment of new boxwood hedges. If planting a new area, use a more tolerant cultivar to lessen your disease pressure in subsequent years. See http://plantpath.cals.ncsu.edu/ornamentals for more information on Boxwood Blight and links to Dr. Ivors’ research trials.

Inquiries about Fairy Ring, Mushrooms, and puffballs in turfgrass continue to be common

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Inquiries about fairy ring, mushrooms and puffballs in turfgrass continue to be common

There are three types of fairy rings based on the symptoms they produce.

  1. Type I. Grass is badly damaged or killed.
  2. Type II. Grass growth is stimulated.
  3. Type III. Grass growth is not influenced by the fairy ring. The only evidence of the fairy ring is the presence of fungal fruiting bodies.

The type III fairy ring symptoms are more predominant during prolonged periods of wet weather, while Type I and Type II fairy ring symptoms are common during hot, dry weather in the summer.

The most effective means for fairy ring control is to prevent the causal fungi from becoming established in the turf. It’s advisable to remove large pieces of woody material such as stumps, dead tree roots and other organic/woody debris before turf is planted to prevent the establishment of fairy rings.

Fairy rings thrive on organic matter; therefore, changing the organic content in the soil by spike/core aeration and thatch reduction can help to control fairy ring. Water and fertilize declining area inside ring appropriately to stimulate new turfgrass growth.

In golf course settings, the use of fungicides is an option to control fairy ring while corrective cultural measures are taken.

More information on fairy ring can be found at:

Turfgrass Diseases in Georgia: Identification and Control

Turf Disease Control Recommendations

Fall Turfgrass Disease Control

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Severe leaf and crown rot, caused by Bipolaris sp. can occur in bermudagrass lawns, sport fields, or golf fairways. Initial symptoms of this disease include brown to tan lesions on leaves. The lesions usually develop in late September or early October. Older leaves are most seriously affected.

Under wet, overcast conditions, the fungus will begin to attack leaf sheaths, stolons and roots resulting in a dramatic loss of turf. Shade, poor drainage, reduced air circulation; high nitrogen fertility and low potassium levels favor the disease.

To achieve acceptable control of leaf and crown rot, early detection (during the leaf spot stage) is a crucial.

Large Patch

Large patch disease of turfgrass is most common in the fall and in the spring as warm season grasses are entering or leaving dormancy. Large patch is caused by the fungus Rhizoctonia solani. It can affect zoysiagrass, centipedegrass, St. Augustinegrass and occasionally bermudagrass.

Large patch disease is favored by:

  • Thick thatch.
  • Excess soil moisture and poor drainage.
  • Too much shade, which stresses turfgrass and increases moisture on turfgrass leaves and soil.
  • Early spring and late fall fertilization.

If large patch was diagnosed earlier, fall is the time to control it. There are a myriad of fungicides that can help to control the disease. Preventative or curative rates of fungicides (depending on the particular situation) in late September or early October and repeating the application 28 days later are effective for control of large patch during fall. Fall applications may make treating in the spring unnecessary. Always follow label instructions, recommendations, restrictions and proper handling.

Cultural practices are very important in control. Without improving cultural practices, you may not achieve long term control.

  • Use low to moderate amounts of nitrogen, moderate amounts of phosphorous and moderate to high amounts of potash. Avoid applying nitrogen when the disease is active.
  • Avoid applying N fertilizer before May in Georgia. Early nitrogen applications (March-April) can encourage large patch.
  • Water timely and deeply (after midnight and before 10 AM). Avoid frequent light irrigation. Allow time during the day for the turf to dry before watering again.
  • Prune, thin or remove shrub and tree barriers that contribute to shade and poor air circulation. These can contribute to disease.
  • Reduce thatch if it is more than 1 inch thick.
  • Increase the height of cut.
  • Improve the soil drainage of the turf.

See the current Georgia Pest Management Handbook for more information. Check fungicide labels for specific instructions, restrictions, special rates, recommendations and proper follow up and handling.

Spring Dead Spot of Bermudagrass

The causal agents of Spring Dead Spot (SDS) are most active during cool and moist conditions in autumn and spring. Appearance of symptoms is correlated to freezing temperatures and periods of pathogen activity. Additionally, grass mortality can occur quickly after entering dormancy or may increase gradually during the course of the winter. Spring dead spot is typically more damaging on intensively managed turfgrass swards (such as bermudagrass greens) compared to low maintenance areas.

Management of Spring Dead Spot

Practices that increase the cold hardiness of bermudagrass generally reduce the incidence of spring dead spot. Severity of the disease is increased by late-season applications of nitrogen during the previous fall.

Management strategies that increase bermudagrass cold tolerance such as applications of potassium in the fall prior to dormancy are thought to aid in the management of the disease. However, researchers have found that fall applications of potassium at high rates actually increased spring dead spot incidence. Therefore, application of excessive amounts of potassium or other nutrients, beyond what is required for optimal bermudagrass growth, is not recommended.

Excessive thatch favors the development of the disease. Therefore thatch management is important for disease control,

  • Implement regular dethatching and aerification activities.
  • There are several fungicide labeled for spring dead spot control.
  • Fall application of fungicides is essential for an effective control.

Publication on Identification and Control of Spring Dead Spot

Additional information can be found at:

Turfgrass Diseases in Georgia

Georgia Turf

Pest Management Handbook (Follow all label recommendations when using any pesticide)

Methods to Maximize Efficacy of Turfgrass Fungicides

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Alfredo Martinez, UGA Plant Pathologist

Weather conditions have been conducive for turfgrass diseases. We have received numerous calls and emails about proper control strategies, especially on the appropriate selection of turfgrass fungicides and their efficacy. Some ways to maximize the efficacy of turfgrass fungicides include:

  • Read carefully and follow the label directions before applying fungicide.
  • Apply fungicides at the rate specified on the label.
  • Always follow instructions for re-entry to the area.
  • Fungicides are not equally effective on all diseases. Proper fungicide selection is very important for disease management.
  • The best control is achieved by applying fungicides preventively (before disease is present).
  • Use compatible tank mixes at recommended label rates.
  • Use proper sprayer, nozzles and pressure to deliver appropriate coverage of fungicides. Flat fan or swirl chamber (raindrop) nozzles are recommended for turfgrass fungicide applications.
  • Avoid turfgrass stress (drought or temperature) before or at the time of application. This could interfere with maximum fungicide uptake, activity and efficacy.
  • Fungicides should be sprayed when air temperatures are between 60°F and 85°F (15°C and 29°C) for best results.
  • Fungicides should stay on the turfgrass foliage for at least 6 hours for most effective control. Delay mowing and other cultural practices as much as possible to give the fungicide a chance to work (for proper mowing frequency follow the one-third rule).
  • Use enough water when applying fungicides for adequate coverage. Usually 2.0 gal water/1000 sq. ft. should give adequate coverage and deposition. Some fungicides have to be watered-in for proper placement to ensure adequate activity.
  • Do not apply fungicides when conditions are windy to avoid drift and poor coverage. Wind velocity tends to be the lowest early in the morning and late in the afternoon.
  • Be patient if an application appears to have produced no results. Some fungicide application results can be seen months later.
  • Use fungicides judiciously and sparingly.

Some notes on Fungicide Resistance

Fungi sometimes develop resistance to particular fungicides, especially when a product is used repeatedly without alternating with chemically unrelated fungicides. When fungicide resistance develops, there is no value in increasing rates, shortening intervals between sprays, or using other fungicides with similar modes of action.

Fungicide resistance has been confirmed in a few instances for each of the following turfgrass diseases and fungicide groups:

  • Dollar spot against benzimidazole fungicides (thiophanate methyl) and DMI fungicides (propiconazole)
  • Gray leaf spot against strobilurin (QoI) fungicides (e.g. azoxystrobin, etc.)
  • Anthracnose against benzimidazoles (thiophanate methyl) and strobilurins (QoI) (azoxystrobin, etc.)
  • Pythium blight against phenylamide fungicides (mefenoxam)

Benzimidazoles (e.g. thiophanate methyl) and phenyl amides (e.g., mefenoxam) have the highest risk of resistance.

Strobilurins have a moderately high risk of resistance

DMIs and the dicarboximides (e.g. iprodione) have a moderate risk

Nitriles (e.g. chlorothalonil), aromatic hydrocarbons (e.g. PCNB), and dithiocarbamates (e.g. mancozeb) have a low risk of resistance.

Several general strategies are recommended to minimize the risk of fungicide resistance.

  • First, don’t rely on fungicides alone for disease control.
  • Avoid using turfgrass varieties that are highly susceptible to common diseases and follow good disease management practices.
  • Also, limit the number of times at-risk fungicides are used during a growing season and alternate at-risk fungicides with fungicides in a different chemical group (those with a different FRAC numeric code).
  • When using an at-risk fungicide, tank-mixing it with another fungicide from another chemical group (different mode of action) can also reduce the risk of resistance.

These are general principles that can help to reduce, but not eliminate risk. A fungicide-resistant pathogen population can still develop when these principles are practiced. Refer to product labels before tank-mixing products to ensure compatibility and to avoid phytotoxicity.

For major chemical group description, see the Georgia Pest Management Handbook – turf disease control section.

Largest Mushroom Species in the Western Hemisphere Found Growing in Georgia

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Jeff DeLong, Undergraduate Researcher, Department of Plant Pathology
Marin Talbot Brewer, Assistant Professor, Department of Plant Pathology

See the original article here

Mushrooms from clusters of M. titans
Mushrooms from clusters of M. titans

Macrocybe titans is the largest gilled mushroom of any species in the Western Hemisphere, with caps in excess of 100 cm (3 ft). These giant mushrooms often occur in clusters within the tropics and subtropics of the New World, with previous sightings reported in the Caribbean, Central America, Mexico, South America, and only in Florida within the USA. Confirmation of this species in Georgia now extends the previously known range of M. titans. To our knowledge, this is the first report in Georgia. The mushrooms were discovered in October 2012 in the yard of an abandoned house in Athens. The fungus was identified as M. titans based on morphological features, habitat where it was found and DNA sequence similarity with known specimens.

The large, cream to buff-colored mushrooms were found growing in three large, dense clusters of eight to 10 mushrooms each (Figure 1). Single caps were 20-30 cm (8-12 in) across and convex with incurving at the margin. Younger mushrooms (Figure 2) had more convex caps than those of older specimens that became flattened with age. The smooth, dry surfaces of the caps were cinnamon-buff in color at the crowns fading to cream toward the margins. The inner flesh of the caps was white. The spore print, which was obtained by placing a cap on half white and half dark-colored paper and covering it with a bowl overnight, was creamy white (spore prints are necessary for proper mushroom species identification).

The stipes (stems) of the mushrooms were cream to buff measuring 30-45 cm (12-18 in) in length (Figure 3). They were club-shaped, tough and fibrous with bent-back scales and striations that curved around the stipe like stripes on a candy cane. The dense clusters of mushrooms were formed by the attachment of individual stipes at the base. Several miniature mushrooms less than 2.5 cm (1 in) in height were found attached to the base of the clusters. The cream to dull-yellow gills of the mushrooms were wavy, crowded and attached to the stipes. The species of the mushroom-producing fungus was confirmed as M. titans by sequencing a region of its DNA.

The mushrooms of M. titans, like the fruiting bodies of any fungus, are the reproductive structures where the spores are produced. The majority of the fungus is actually growing as filamentous hyphae underground and out of sight in decomposing dead and decaying plant matter in the soil. The three nearby clusters that were observed likely came from a single individual growing in the soil beneath the tall grass. M. titans is saprotrophic, which means that it decomposes dead or decaying plant matter and does not cause disease or rot on living grasses or trees.

It is not clear why or how this fungus found its way into Georgia. The mushrooms were close to landscape ornamental grasses and it may have arrived with the container plants, as Florida is a large producer of ornamental landscape plants. Or, it may be expanding its geographic range into Georgia due to climate warming or some other factor. This species was previously known as Tricholoma titans, but in 1998 was renamed Macrocybe titans, which literally translates from Latin into “giant large head.” The mushrooms are reportedly edible; however, never consume a wild mushroom without identification confirmation by an expert. Contact your county Extension office should you happen to encounter the giant mushrooms of M. titans.

We thank Kirk Edwards for discovering these mushrooms and contacting us about their identification.

References:

Bessette, A.E., Roody, W.C., Bessette, A.R., and Dunaway, D.L. 2007. Mushrooms of the Southeastern United States. Syracuse University Press, Syracuse, NY.

Bigelow, H.E., and J.W. Kimbrough. 1980. Tricholoma titans, a new species from Florida. Mycotaxon 11: 425- 429.

Pegler, D.N., Lodge, D.J., Nakasone, K.K. 1998. The pantropic genus Macrocybe gen. nov. Mycologia 90: 494-504.

Wood decay and falling trees are of great concern

by

Jean Williams-Woodward, UGA Extension Plant Pathologist

Damage from past years of drought has taken a toll on our trees. Drought stress, construction injury, soil compaction and root girdling injures tree roots and provides an entry point for wood decay fungi. Storm damage, improper pruning, and wounding of trunks and branches also leads to wood decay fungi entry and infection.

Wood decay fungi can be classified into two broad categories: white-rot and brown-rot fungi.

White-rotters are those fungi that rapidly breakdown lignin and eventually cellulose. The infected wood becomes soft, spongy and stringy. It is usually a root and butt rot by a white-rot fungus that causes hardwood trees to fail and fall (see images of Inonotus dryadeus).

Brown-rotters are those fungi that breakdown cellulose and eventually lignin. Wood crumbles and shrinks. These rots are often referred to as a cubical or dry rot.

Regardless of the type of rot and what fungus is infecting the tree, if you see conks or mushrooms growing on the tree trunk or root flare, then the tree is in advanced stages of infection and decay and there is a concern for possible tree failure. It takes years for infection and growth of the fungus in the wood to produce outward signs of conks and mushrooms.

At present, methods to accurately detect how much rot is present in the wood do not exist. There are methods to detect internal cavities in trees to determine the thickness of a trunk shell, but measurements of spongy wood is difficult. There is no cure for wood decay. The best management approach is preventing injury to trunks, branches, and roots.

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