Landscape Alerts & Updates | September 2019


Insufficient production and storage of photosynthates during the fall transition into dormancy can translate to issues during spring green-up.  Drought stressed turfgrass in August 2016 (Left) was able to recover prior to dormancy following appreciable rainfall (Right). However, we are seeing drought-stressed turfgrass in September of 2019 and the dormancy transition is quickly approaching.  Photo by Clint Waltz, UGA.

Tips for managing drought stressed turfgrass as dormancy approaches

by Clint Waltz

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 from May to October. 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 2019 has delivered hot and dry weather with sporadic rainfall.  With fall approaching, now is the time to adjust your turfgrass management program to promote a smooth transition into dormancy and green-up next spring.

From mid- through late-summer rainfall across Georgia has been variable with some areas receiving timely rain and other areas being droughty.  Moisture stress in turfgrasses can be recognized in the early stages by a dull bluish-gray cast.  Additionally, take note of footprints and tire tracks in the turf that do not seem to rebound.  If you are in an area that has lacked rain, consider applying some irrigation to get the grass growing.

Dr. Clint Waltz, UGA Extension Turfgrass Specialist, suggests these tips for managing turfgrass as it transitions into dormancy:

  1. Raise the cutting height within the recommended mowing range
  2. Do not apply nitrogen containing fertilizers
  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.

Avoid Nitrogen Applications

As grasses move into dormancy they need to “harden-off”.  Nitrogen fertilization encourages new shoot growth which directs plant sugars, and other metabolites, away from storage organs (e.g. rhizomes, stolons, and crown).  These storage organs and sugars provide the energy for the grass to green-up next spring. By allowing the plant to harden-off and accumulate sugars in the storage structures, the grass is better able to survive winter stresses and recover next year.

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.  The 2010 Water Stewardship Act permits lawn watering between the hours of 4:00pm and 10:00am.

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 cultivars such as TifTuf bermudagrass.  Visit www.GeorgiaTurf.com for more information on selecting turfgrasses.

Landscape Alerts & Updates | June 2019

Photo by Clint Waltz, UGA.

Nostoc Algae in Turfgrass

Guest post by Clint Waltz, Ph.D., University of Georgia Turfgrass Specialist.
(Turfgrass Blog #4: 2019 Edition, June 10, 2019)

With the recent dry weather encouraging the use, and possible overuse, of irrigation systems then the recent tropical conditions – rainfall and humidity – I have had several pictures and questions about a jelly-like substance growing in the turf.  The jelly-like “stuff” is a Nostoc algae,a genus of cyanobacterium formerly classified as blue-green algae.  It has multiple common names like star jelly, witch’s butter, and others.

Under warm temperatures Nostoc may appear suddenly in lawns, and other turf areas, following a period of rain and can be an indication of overwatering.  In turf, it is generally on a site where the grass is growing poorly due to severe compaction, overwatering, or both.  It does not cause turf decline or death; it colonizes areas where it has favorable growing conditions and the grass was already thin.  Poor drainage and compacted soils create a favorable environment for Nostoc. It will dry-out if the water or rainfall diminishes but it has only gone into dormancy.  With enough moisture, it will come back to “life”.

In its hydrated, gelatinous, green state it can be a safety hazard.  It is slippery.  Be careful walking on it.  However, when it dries-out it can become restrictive to turfgrass growth.  Nostoc dries into a black crust that can prevent stolons from rooting, or “tacking”, into the soil, delaying turfgrass growth and spread.

Nostoc can be difficult to control.  To discourage its growth, encourage the growth of the grass.  Algae is less of an issue with an actively growing turfgrass canopy.  The first step is to check the irrigation system to make sure it is watering properly (i.e. not too regular or too much).  The turfgrass species we grow in Georgia perform better when grown on the slightly dry side, so scaling back the irrigation and adjusting the irrigation schedule will benefit the grass and can discourage the algae.

Improve internal soil and surface drainage.  Core aeration opens the soil, allows oxygen into the root system, and reduces compaction.  While allowing the soil surface to dry-out then breaking up the Nostic “crust” by scarifying the upper ¼- to ½-inch can break the algae into pieces and encourage its spread, it also permits the turfgrass stolons to root into thin areas and outcompete the Nostoc.  With proper irrigation and core aerification the grass can cover and eventually predominate the area where the Nostoc was present.

For more information on Nostoc Algae, contact your local UGA Extension Agent at 1-800-ASK-UGA1, or click below to find your local office information.

 

Controlling Moss and Algae in Turf, UGA Extension Circular #823.
https://extension.uga.edu/publications/detail.html?number=C823&title=Controlling%20Moss%20and%20Algae%20in%20Turf

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

Landscape Alerts and Updates – MAY 2017

Slime Mold on Turfgrasses

Has your lawn been slimed?  Fear not, the grayish-black sooty substance on your turfgrass is a harmless soil protozoa that has temporarily migrated onto blades and stems to produce and disperse spores.  Diagnosis: Slime Mold,  Physarum and Fuligo sp./spp.  The occurrence is prompted by spells of humid, rainy weather during spring and early summer and is typically short-lived (1-2 weeks).  Aside from temporarily hindering photosynthesis, slime molds do not parasitize or damage the turfgrass.   Slime mold can be ignored, mowed, raked, or washed off with a pressurized stream of water.

Related Articles: what-is-this-unusual-growth-on-lawns


Lawn Burweed

If you missed the window of opportunity to manage burweed in your lawn in late winter/early spring, then you may be feeling it, literally!  The seed burs are now mature and a barefoot stroll across the lawn may inflict you with some painful hitchhikers.  At this point, applying a broadleaf herbicide product may kill the weed, but will not eliminate the existing burs that have formed, so mark your calendars for burweed scouting and control next February.  If an immediate solution is needed, locate individual plants and physically remove them.  Burweed tends to colonize compacted bare areas. For large areas of infestation it may be necessary to scalp and bag the clippings with a mower to remove the burs, followed by turfgrass renovation or establishment on those areas (assuming that you have a warm-season turfgrass species such as bermudagrass, it would not be advisable to scalp a Tall Fescue lawn in May).  For more information on scouting for lawn burweed, refer to the previous post “Winter Scouting for Lawn Burweed.”

Related articles: winter-scouting-for-burweed-soliva-pterosperma


Turf Aerification

Now is the time to aerify warm-season turfgrasses.  Last year, the dry conditions persisting from August through December depleted carbohydrate reserves in warm-season turfgrasses. A delay in turfgrass green-up was common this spring and warm-season turfgrasses are poised to replenish carbohydrate reserves and restore root systems.  “If there is a year to seriously consider core aerification, this is it,” says Dr. Clint Waltz, a Cooperative Extension turfgrass specialist with the University of Georgia College of Agricultural and Environmental Sciences.  Core aerification relieves compaction, improves air exchange and water infiltration, and stimulates deeper root growth.  Hollow-tine aerification is the preferred method, removing soil cores to a depth of 3-4 inches, and having longer-lasting benefits.  A light fertilizer application in concert with aerification can be beneficial, but heavy nitrogen applications should be avoided to allow for the replenishment of carbohydrate reserves (over-stimulating top growth depletes carbohydrates reserves).

To make sure soil pH, phosphorus and potassium levels are within recommended ranges for optimum growth, take a soil sample to your local University of Georgia Cooperative Extension office.

Read the full article on Core Aerification and find lawn care calendars for different turfgrass species at www.GeorgiaTurf.com .

Related Articles and Publications:

Turfgrass Fertility: Soil Texture, Organic Matter, Aeration, and pH (C 1058-1)


 

 

Aerification: Restoring Turfgrass Carbohydrate Reserves

Dr. Clint Waltz, Extension Turfgrass Specialist with the University of Georgia, reports that hot temperatures and low rainfall in the fall of 2016 likely sent warm-season turfgrasses into winter dormancy with depleted carbohydrate reserves. During “normal” circumstances warm-season turfgrasses accumulate and store carbohydrates from late summer through early fall.  Last year, non-irrigated turfgrasses likely suffered drought-induced dormancy and transitioned to winter a weakened condition.  With insufficient energy accumulated in root systems, a thin canopy and a two- to four-week delay in the green-up of warm-season grasses might be common this spring.

 

 

 

 

 

 

What can be done to improve the green-up and growth of warm-season turfgrasses this spring?

1) AERIFICATION – Core aerification in late April to mid-May.  This will improve air exchange and water infiltration to stimulate root and shoot growth.  Performing hollow-tine aerification that removes 1/2 inch diameter soil cores to a 3 or 4 inch depth is the recommended approach.

2) TIMING OF FERTILIZER – Withhold the application of nitrogen fertilizer until soil temperatures at the 4-inch depth are consistently 65 degrees and rising.  Visit www.Georgiaturf.com to find lawn calendars that include fertility recommendations for each species.  Soil temperature data from the Georgia Automated Environmental Monitoring System can be found at www.Georgiaweather.net.

3) SOIL TESTING – Collect a soil sample and submit for testing to ensure that soil Ph, phosphorous, and potassium levels are within the recommended ranges for optimum growth.  Contact your local UGA Extension Agent about submitting a soils sample to the UGA Agriculture and Environmental Services Laboratory or call 1-800-ASK-UGA1.

Restoring carbohydrate reserves this spring is an important step in preparing turfgrasses for a healthy growing season.  Read the full article by Dr. Clint Waltz at www.Georgiaturf.com.