Landscape Alert – September 2017

Fall Turfgrass Disease Prevention and Control  

by Alfredo Martinez

Large Patch

Rhizoctonia large patch is the most common and severe disease of warm season grasses (bermudagrass, centipedegrass, seashore paspalum, St. Augustinegrass, and zoysiagrass) across the state of Georgia. Due to spring and fall disease-promoting environmental conditions across Georgia coinciding with grasses leaving and/or entering dormancy, large patch can appear in warm season grasses in various grass-growing settings, including home lawns, landscapes, sports fields, golf courses, and sod farms. Symptoms of this lawn disease include irregularly-shaped weak or dead patches that are from 2 feet to up to 10 feet in diameter. Inside the patch, you can easily see brown sunken areas. On the edge of the patch, a bright yellow to orange halo is frequently associated with recently affected leaves and crowns. The fungus attacks the leaf sheaths near the thatch layer of the turfgrass.

photo of turfgrass disease large patch

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 Nitrogen fertilization.

If large patch was diagnosed earlier, fall is the time to control it. There is a myriad of fungicides that can help to control the disease. Fungicides in the following classes are labeled for large patch control: carboxamides, benzimidazoles, carbamates, dicarboximides, DMI fungicides, di-nitro anilines, control. For a complete and updated list of fungicides available for commercial control of large patch, visit http://extension.uga.edu/publications/detail.cfm?number=SB28  or http://www.commodities.caes.uga.edu/turfgrass/georgiaturf/Publicat/1640_ Recommendations.html.  Preventative or curatives (depending on the particular situation) rates of fungicides 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. Reduced mowing heights result in a more dense turf stand, which may create a more favorable environment for large patch development
  • Improve the soil drainage of the turf.
  • Control traffic patterns to prevent severe compaction, and core aerate to improve soil drainage and increase air circulation around the shoots and root

For more information on large patch visit https://secure.caes.uga.edu/extension/publications/files/pdf/C%201088_2.PDF

  

Spring Dead Spot of Bermudagrass

Fall cultural practices and fungicide applications are key for Spring Dead Spot management. The disease is caused by fungi in the genus Ophiosphaerella (O. korrae, O. herpotricha and O. narmari). These fungi infect roots in the fall predisposing the turf to winter kill.  As indicated by its name, initial symptoms of spring dead spot are noticeable in the spring, when turf resumes growth from its normal winter dormancy.  As the turf ‘greens-up,’ circular patches of turf appear to remain dormant, roots, rhizomes and stolons are sparse and dark-colored (necrotic).  No growth is observed within the patches.  Recovery from the disease is very slow. The turf in affected patches is often dead; therefore, recovery occurs by spread of stolons inward into the patch.  The causal agents of 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.

photo of turfgrass disease 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.
  • Timing, selection and application of fungicides are important for preventative management of SDS. Fungicide application in the fall when soil temperatures are between 60° and 80° F provides the best control of SDS
  • A complete list of fungicides, formulations and product updates for SDS can be found in the annual Georgia Pest Management Handbook and the Turfgrass Pest Control Recommendations for Professionals (http://www.georgiaturf.com). Some fungicide options are exclusively for golf course settings. Always check fungicide labels for specific instructions, restrictions, special rates, recommendations, follow-up applications and proper handling.

For more information on SDS visit https://secure.caes.uga.edu/extension/publications/files/pdf/C%201012_3.PDF

 

Early detection of bermudagrass leaf spot 

Severe leaf and crown rot, caused by Bipolaris ssp. 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.

Photo of turfgrass disease Bermudagrass Leaf SpotPhoto 2 of turfgrass disease Bermudagrass Leaf Spot

Dollar spot is still active in the fall/early winter

Dollar spot is most prevalent during spring and fall with infections developing rapidly at temperatures between 60 and 75 degrees Fahrenheit combined with long periods of leaf wetness from dew, rain, or irrigation.

  • Excessive moisture on turfgrass foliage will promote dollar spot epidemics. Irrigating in the late afternoon or evening should be avoided, as this prolongs periods of leaf wetness.
  • If feasible, prune or remove trees and shrubs to promote air movement and accelerate drying of the turfgrass canopy
  • A variety of fungicides are available to professional turfgrass managers for dollar spot control including fungicides containing benzimidazoles, demethylation inhibitors
    (DMI), carboximides, dicarboximides, dithiocarbamates, nitriles and dinitro-aniline. Several biological fungicides are now labeled for dollar spot control.
  • For a complete and updated list of fungicides available for dollar spot, visit http://extension.uga.edu/publications/detail.cfm?number=SB28 or http://www.commodities.caes.uga.edu/turfgrass/georgiaturf/Publicat/1640_Recommendations.htm.

photo: turfgrass disease dollar spot photo: turfgrass disease dollar spot2

Additional information on dollar spot visit https://secure.caes.uga.edu/extension/publications/files/pdf/C%201091_2.PDF

A Rough End to the Season for Warm-season Turfgrasses

The lack of rainfall in the second half of the growing season has hindered the production and storage of energy that normally takes place in warm-season turfgrasses from late summer through fall.  In effect, warm-season turfgrasses could enter winter dormancy with depleted carbohydrate reserves.  Dr. Clint Waltz, Extension Turfgrass Specialist with the University of Georgia, is concerned that winter hardiness and spring green-up issues could result from a rough end to the growing season.  The weather over the next few weeks will decide how warm-season turfgrasses cross the finish line into dormancy.

“The limiting factor is water,” said Waltz. The biological activity that is necessary to gather and store carbohydrates requires water and we need some rain.  With soil temperatures at the 4″ depth holding in the 60’s for October and the forecast through the end of the month calling for high temperatures near 80 degrees for much of the state, there may be some opportunity for growth where irrigation is available.  However, gains will be marginal as the day length, temperatures, and radiant heat levels continue to drop.  Applying 1/2″ inch of irrigation per week may be sufficient to help mitigate spring green-up issues and prevent crown desiccation if dry weather continues.  Fertilizer is NOT recommended for warm-season grasses at this point in the season, especially nitrogen.  Applications of potassium are generally recommended to promote winter hardiness, but without adequate water, the benefits of these applications may not be fully realized.

What can turf managers do to prepare?  Irrigate if you can, do not fertilize, minimize mowing and wear damage, and avoid practices such as aeration that would induce additional plant stress as the turfgrass enters dormancy.  When using irrigation systems, be sure to follow the parameters of the Georgia Water Stewardship Act of 2010 and stay informed on the latest drought information at www.georgiawatersmart.com. For more information on landscape watering visit www.Georgiaturf.com and download the publication “Best Management Practices for Landscape Water Conservation.” Most importantly, contact your local UGA County Extension Agent at http://extension.uga.edu/about/county/index.cfm or call 1-800-ASK-UGA1

Water Conservation and Drought Awareness: Information about the Georgia EPD Drought Level 1 Response

On September 9, 2016, a drought level 1 response was issued by GEPD for 53 counties in northwest and central Georgia. Georgia’s drought management plan, as outlined by the Georgia Water Stewardship Act of 2010, establishes a three-tiered approach to water resource conservation and monitoring.  The first tier of the system is called “Drought Level 1” and initiates a conservation and public awareness campaign by local water utilities in affected counties. Look for forthcoming information regarding the drought level 1 response from local water authorities in these counties to help citizens better understand drought, its impact on water supplies and the need for indoor and outdoor water conservation.  drought_level_1_9-15-2016

 

Outdoor watering: Is it okay to plant trees and irrigate turfgrass?  Yes, normal outdoor watering is allowed between the hours of 4pm and 10am and new landscapes can be watered any day, any time for 30 days in accordance with the Georgia Water Stewardship Act. However, proper plant care and responsible watering practices should always be followed.

Contact your local University of Georgia Extension Agent for scientific publications, bulletins, and fact sheets regarding plant care and irrigation practices. Key practices include mulching, proper plant selection, raising mower heights, and proper irrigation.  In addition, the Georgia Urban Ag Council and the Georgia Green Industry Association launched a website called Georgiawatersmart.com outlining best management practices for indoor and outdoor water conservation.

According to the 2012 Annual Report, the Metropolitan North Georgia Water Planning District estimates that the 15 County Metro Atlanta area reduced per capita water consumption by as much as 20% between 2000 to 2010 through local water stewardship and conservation efforts. Spread the word about water conservation and drought awareness and stay informed on the latest practices for managing drought stressed landscapes.  For more information about the level 1, 2, and 3 drought responses, visit the Water Conservation page of the Georgia Environmental Protection Division website.

Related Articles:

Tips for Managing Drought Stressed Turfgrass

Drought Level 1 Declared in Georgia

 

 

Tips for Managing Drought Stressed Turfgrass

Turfgrass_Drought

Tips for Managing Drought Stressed Turfgrass

During periods of hot and dry weather, certain modifications to your lawn maintenance practices will help to carry your turfgrass through periods of inadequate rainfall and reduce losses. The height of the warm-season turfgrass growing season spans May through August. Given average conditions (regular rainfall and moderate temperatures), bermudagrass, zoysiagrass, St. Augustinegrass, centipedegrass, and other warm-season species respond quickly to cultural and maintenance practices such as mowing, fertilizing, aerating, topdressing, and weed management.  However, the summer of 2016 has delivered hot and dry weather with less than normal rainfall.  With August approaching, now is the time to fine tune your turf management program to salvage an acceptable appearance while minimizing growth until environmental factors improve.

The first order of business is to recognize moisture stress in turfgrasses in the early stages.  Look for areas with a dull bluish-gray cast. Additionally, take note of footprints and tire tracks in the turf that do not seem to rebound.

Dr. Clint Waltz, UGA Extension Turfgrass Specialist, suggests these tips for managing turfgrass during drought periods:

  1. Raise the cutting height within the recommended mowing range
  2. Reduce fertilizer applications until conditions improve
  3. Modify herbicide programs during high temperatures and moisture stress
  4. Water deeply & Infrequently
  5. Grasscycle
  6. Use water conserving and drought tolerant turfgrasses

Raise the Cutting Height

Turfgrass stress can be reduced by using a sharp mower blade and raising the cutting height by 1/2″ or to the tallest allowable height of the recommended mowing range during drought.  A clean cut also reduces moisture loss through wounds and minimizes entry points for disease.  Taller shoots promote deeper roots and a dense canopy can help to reduce ground surface temperatures and conserve moisture.  Grasscycling (mulching clippings versus bagging) can also help to conserve moisture.

Reduce Nitrogen Applications

Plant growth requires water.  Without water, the benefits of nitrogen are not optimized and you may be wasting product. Promoting heavy top growth amidst drought conditions increases water demand. Reduce rates or postpone fertilizer applications until environmental conditions improve to fully realize the benefits of fertilizer while saving water and reducing turfgrass stress.

Modify Herbicide Programs During High Temperatures and Drought

Many herbicides act upon plant growth processes and can be less effective during periods of drought when weeds are not actively growing. In addition, certain herbicides may cause damage to drought-stressed turf or non-target landscape plants due to volatilization and drift during high temperatures. Review your pesticide labels for specific information regarding temperature requirements, watering requirements, and proper application.

Water Deeply and Infrequently

The optimum watering schedule can be roughly determined by observing the number of days that pass between signs of moisture stress. Apply sufficient water to saturate the root zone to a depth of 6-8 inches.  Clay soils and sloped areas may require staggered watering intervals to allow time for water infiltration between cycles and prevent runoff.  Irrigating in early morning conserves water by reducing evaporation and drift.  A good practice is to align watering schedules with drought management rules so that in the event of a declared drought, the appropriate watering program is already in place.  As of July 26, 2016 there are no official declarations of drought by state or local authorities in Georgia and responsible landscape and lawn watering may take place between the hours of 4:00pm and 10:00am in accordance with the Georgia Water Stewardship Act of 2010. In the event that water resources require a drought response level 2, watering programs would need to be adjusted for the odd-even schedule by address.

Use Water Conserving and Drought Tolerant Turfgrass Cultivars

The University of Georgia Turfgrass breeding programs continue to make excellent strides in developing improved cultivars with low water use and high drought tolerance. For new installations or where turfgrass replacement is needed, look for improved certified cultivars such as TifTuf bermuda.  Visit www.GeorgiaTurf.com for more information on selecting turfgrasses.


THE LOOK AHEAD: JULY & AUGUST

DATE:TITLEDESCRIPTIONDETAILS
July 27UAC Industry Issues Lunch + Learn.

Details & Registration

Beat the Heat and Earn 2 Category 24 GA Pesticide Recertification Credits or 1 PrivateLOCATION: Snellings Walters Insurance Agency, 1117 Perimeter Center W, Atlanta GA 30338
TIME: 11:30 am – 1:30 pm
COST: $20 for UAC members/$25 for visitors. Registration includes lunch.
August 4UGA Turfgrass Research Field Day

Details & Registration

Acres of Information & CEU Credits.  Discover the latest turfgrass information, products, and equipment.LOCATION: UGA-Griffin Campus 1109 Experiment Street
Griffin, GA 30223
TIME: 8:00 am – 2:30 pm
COST: Visit georgiaturf.com for Registration Details
August 9Georgia Certified Plant Professional  (Plant ID & Written Exams)

Details & Registration

The Georgia Center for Urban Agriculture Offers Achievement, Advancement, & Credibility through Professional Certification.LOCATION: Gwinnett Technical College
5150 Sugarloaf Pkwy, Lawrenceville, GA 30043
TIME: 9:30 am – 1:30 pm
COST: $165 For details, visit gcpp.info
August 31 – September 1SEGreen Landscape & Plant Conference

Details & Registration

See, hear, and make more green at SEGreen, the roadmap to the future for Southeast growers, landscapers, and retailers.LOCATION: Athens Classic Center
300 N Thomas St, Athens, GA 30601
TIME: 7:00 am – 6:00 pm
COST: For details, visit segreen.org
August 31 – September 1(SEGreen Conf.)
Georgia Certified Landscape Professional (Written & Hands-On Exams)Details & Registration
The Georgia Center for Urban Agriculture Offers Achievement, Advancement, & Credibility through Professional Certification.LOCATION: Athens Classic Center
300 N Thomas St, Athens, GA 30601
TIME: 7:00 am – 6:00 pm
COST: $165 For details, visit gcpp.info

Spring Green Up: Timing Nitrogen Applications by Temperature

“When soil temperatures consistently measure 65 degrees (F) at the 4″ depth and are trending upwards, it’s time to fertilize warm-season turf,” says Dr. Clint Waltz, UGA Turfgrass Extension Specialist.  Resisting the temptation to fertilize warm-season turf too early in the season not only conserves valuable time and resources, but encourages a healthy competitive lawn.  Spring season air temperatures often fluctuate from lows in the mid 40’s to highs in the mid 70’s, resulting in wide swings in soil temperature.  The best time to fertilize warm-season turfgrasses such as bermudagrass, zoysiagrass, St. Augustinegrass, and centipedegrass is during the active growth season spanning May through August when air temperatures reach highs in the mid 80’s to 90’s and soil temperatures remain well above 65 degrees.

Read more

Winter Bloom: Will the Azaleas Flower Again this Spring?

Dr. Bodie Pennisi, University of Georgia Horticulture Extension Specialist, reports that the azaleas will likely still bloom, only with a few less flowers.  “Many of the flower buds remained dormant during the warm spell. Keep in mind however, that the flower buds on azaleas developed last summer and any pruning done prior to the spring will potentially remove those flower buds.” The same applies to Hydrangea macrophylla (Bigleaf Hydrangea) and H. quercifolia (Oakleaf Hydrangea). Microclimates also affect cold damage, for example, overhangs, tree canopies, evergreen shrubs, and built features in the landscape often provide frost protection, buffer against radiant heat loss, and provide wind breaks.  Flower buds can be inspected for cold damage by opening a bud and looking for brown or black water-soaked tissues, indicating ruptured cells.

So far, January has delivered steady cool temperatures and allowed most plants to adjust to the cold with minimal damage.  Typically, it is the rapid fluctuations from warm to cold that cause issues, so we shall see what unfolds over the next few weeks.

Suggested Readings:

Westerfield, R., Lindstrom, O. PhD, (2015). UGA Extension Bulletin (C 872). “Winter Protection of Ornamental Plants.”

The Rains and Unusual Weather of December 2015

Winter Arrives after Unusual December

The conclusion of 2015 marked one of the soggiest Decembers on record with many areas of the state receiving in excess of 13 inches for the month (roughly 20% of the annual rainfall.) In addition, high temperatures hovered in the mid 70’s for much of December leaving Bermuda lawns green and irises, roses, magnolias, and azaleas blooming.  Perpetual rainfall kept soils waterlogged for an extended period of time and many folks ended the season wondering how the unusual weather might affect their gardens.

Total Precipitation – December 20152014
Blairsville13.35”3.06”
Griffin13.94”5.41”
Tifton8.41”6.48”

University of Georgia Automated Environmental Monitoring Network

Average Daily Temperatures – December 20152014
Avg. Max. Temp. (°F)Avg. Min. Temp. (°F)Avg. Max. Temp. (°F)Avg. Min. Temp. (°F)
Blairsville62.0141.2154.6833.82
Griffin66.2948.2258.1939.16
Tifton70.6552.4763.9444.59

University of Georgia Automated Environmental Monitoring Network

Will the azaleas bloom again this spring? Read more at www.ugaurbanag.com/Landscape Alerts.