Gray Leaf Spot

By Alfredo Martinez

Gray Leaf Spot


Figure 1 (left) and 2 (right). Gray leaf spot on St. Augustinegrass (images by Alfredo Martinez)

Gray leaf spot (Figure 2) is a fungal disease that affects St. Augustinegrass, perennial ryegrass and tall fescue in Georgia. The disease is particularly aggressive in St Augustinegrass. Hot, humid summer weather and high nitrogen levels can make turf susceptible to this disease. The fungus causing the disease is Pyricularia grisea.

Symptoms: The symptoms of gray leaf spot vary depending on the grass cultivar. On St. Augustinegrass, gray leaf spot first appears as small, brown spots on the leaves and stems. The spots quickly enlarge to approximately ¼ inch in length and become bluish-gray and oval or elongated in shape. The mature lesions are tan to gray and have depressed centers with irregular margins that are purple to brown. A yellow border on the lesions can also occur. In cool-season turfgrass, the symptoms are similar to those of melting out.

Conditions Favoring Disease: Gray leaf spot is favored by daytime temperatures between 80ºF to 90ºF and night temperatures above 65ºF. It is also found in areas with high nitrogen levels and that are stressed by various factors, including drought and soil compaction. This disease is most severe during extended hot, rainy and humid periods.

Disease Management Tips: Management practices that minimize stress and avoid rapid flushes of lush growth during the rainy season lessen the likelihood that severe gray leaf spot symptoms will develop. If irrigation is used to supplement inadequate rainfall, water infrequently but deeply.

Proper irrigation regimens should protect against symptoms of drought stress without increasing disease pressure by extending periods of leaf wetness. Excessive soil moisture and leaf wetness promote gray leaf spot. Irrigating in the late afternoon or evening should be avoided, as this prolongs periods of leaf wetness.

Proper mowing practices are most important for gray leaf spot management in St. Augustinegrass. This grass must frequently be mowed during the summer months to remove excess leaf tissue and keep the canopy open and dry. Mow the turf at the correct height for the designated turfgrass species and remove only one-third of the leaf blade per mowing. Collecting clippings reduces the spread of the disease when gray leaf spot symptoms are evident. Thatch layers should be removed if they are greater than 1 inch in depth.

St. Augustinegrass is especially sensitive to some herbicides. If possible, manage weeds using cultural management techniques and minimal amounts of herbicides. The timing of any atrazine application should be chosen carefully, as this herbicide can stress the grass, especially when temperatures may climb above 85 degrees F. Atrazine applications made before or during disease-favorable conditions increase the likelihood of severe gray leaf spot symptom development. Spot-treating trouble areas with the herbicide may also be considered. Herbicides should always be applied according to the label instruction

Fungicides are available to control the disease. Consult the current Georgia Pest Management Handbookwww.ent.uga.edu/pmh/.

Drought Response Level 2: Outdoor Watering Information

Prolonged dry weather has prompted an elevated drought response for northwest Georgia. Effective November 17, 2016, fifty-two counties have entered a drought response level 2 and fifty-eight counties are exercising a drought response level 1.  Rainfall has been scarce since August and water conservation is the banner message.  The Georgia Water Stewardship Act of 2010 establishes certain outdoor watering protocols to conserve water during times of drought.  These rules apply to all properties served by state permitted water systems.

Highlights of Drought Response Level 1:
A drought response level 1 initiates a public information campaign to explain drought conditions and the need for water stewardship and conservation.  Normal outdoor watering should follow best management practices and is allowed between the hours of 4:30pm and 10am any day of the week.

Highlights of Drought Response Level 2:
For existing landscapes, a drought response level 2 initiates the odd/even watering schedule by address for sprinkler systems.  For even addresses (ending in zero, 2,4,6,8) watering is allowed as needed on Wednesdays and Saturdays between the hours of 4pm and 10am.  For odd addresses (ending in 1,3,5,7,9) watering is allowed as needed on Thursdays and Sundays between the hours of 4pm and 10am.  Sprinkler systems should always be properly maintained and adjusted.  Evapotranspiration is much lower during the fall and winter and minimal irrigation is needed to prevent winter desiccation using a rate of 1/2 inch precipitation per week or less during periods of dry weather.

New Landscapes:
Under all levels of drought response, a 30 day exemption period is allowed for the establishment of new landscapes. Once the establishment period has expired, drought response watering practices should be followed accordingly.

Other Allowable Exemptions:
Handwatering using a hose with an automatic shut-off nozzle
Food gardens
Hydroseeding
Drip irrigation or soaker hoses
Horticulture crops intended for sale, resale, or installation
Athletic fields, golf courses, and public recreation areas
Maintenance or calibration of an irrigation system
Water from private wells and bodies of water on property (not exceeding state withdrawal limits)
Water from an alternate source (grey water, rain water, air-conditioner condensate)
Commercial Pressure Washing

Summary:
Stay informed on the latest drought information for your area (see helpful resources and information below).  While natural precipitation is generally sufficient to prevent plant desiccation in established landscapes during fall and winter, extremely dry conditions may require supplemental watering to help mitigate plant damage. Follow responsible watering practices and properly manage irrigation systems to protect plant health while promoting a culture of water conservation in Georgia.  Register for training opportunities such as the upcoming “Irrigation Training for Landscape Professionals” at the EDGE Expo at the Gwinnett Infinite Energy Center on December 8, 2016.

For more information on proper watering practices and training opportunities, contact your local UGA Extension Agent or call 1-800-ASK-UGA1.

Helpful Resources and Information:
http://extension.uga.edu/publications/
www.GeorgiaTurf.com
www.GeorgiaWatersmart.com
https://epd.georgia.gov/water-conservation

 

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 Bleeding: Maple, Birch, Elm, Grapevines

Following a late winter or early spring pruning of Maple, Birch, Elm, or Grapevines it is common to observe “bleeding” from the pruning wounds.  This phenomenon usually occurs just before and during leaf emergence in the spring, especially during years of abundant soil moisture.  The temporary bleeding is generally not detrimental to the health of the plant and primarily consists of a watery sap solution. The bleeding usually ceases once the leaves have fully emerged and water begins to evaporate through the leaf stomata, creating transpirational pull that overshadows the root pressure.

The upward flow of water is caused by osmotic pressure in the root system that begins with the imbalance of water molecules between the soil and the root system.  A high concentration of minerals and carbohydrates in the root system generally translates to a lower concentration of water molecules when compared to the surrounding soil. Water molecules enter the root cells to equalize distribution, causing root cells to become turgid and force water upwards in the vascular system.  (Incidentally, the reverse is true when too much fertilizer is applied and a higher concentration of minerals in the soil prevents the osmotic absorption of water into the root system.)

Occasionally, bleeding can be a nuisance where these plants drip on parked cars and pedestrian spaces.  In such cases, delay pruning of these species until late spring-early summer to help to reduce the issue.

If prolonged bleeding occurs and you observe any unusual signs or symptoms of pests or disease, report the information to your local extension agent for further assessment.

Lawn and Garden Moisture Index

Information taken from the Climate and Agriculture in the Southeast (CASE) newsletter.

Do things seem really dry where you are?  How much should you water your lawn or irrigate your crops?  There are a number of commercial products out there that can help you determine this, but one simple method that is available for free is the Lawn and Garden Moisture Index, a daily map put out by the Alabama State Climatologist based on estimated rainfall from radar.  This map tells you whether your lawn and garden have enough moisture or if more needs to be added.  This is one of a number of useful products available on AgroClimate.org, a website developed by the Southeast Climate Consortium, a group of eight universities around the Southeast.

lawn-garden-7-8-2014-235x300

This map shows the areas with surplus water in greens (no need to water or irrigate there) and areas with a water deficit in oranges and reds.  The darkest red areas are almost 2 inches short of water, including a large portion of Georgia.  If this situation continues, then the Drought Monitor is likely to add D0, abnormally dry conditions, to the next weekly Drought Monitor map.  Areas with deficits of an inch or more should be irrigated to help alleviate the dry conditions and keep lawns and gardens healthy.