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

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.

Reddish Spots Caused by Spot Anthracnose on Dogwood Leaves

Dogwood spot anthracnose

Disease Symptoms(Reddish Spots):

Small, reddish spots first appear on flower bracts. Reddish spots appear on leaves; leaves become distorted from infection in bud stage. Disease may cause leaves to drop.

Disease Management:

  • Rake and remove fallen leaves.
  • Disease will not cause significant damage to the tree.
  • Fungicides applied at swollen bud stage for flowers and leaves can reduce infection, but are only recommended for young, newly-transplanted trees.
  • Kousa variety is moderately resistant to disease.

Compiled by: Dr. Jean L. Williams-Woodward, UGA Extension Plant Pathology, Athens

Problems Your Extension Agents Are Seeing

Problems Your Extension Agents Are Seeing

Insect Problems

Ambrosia Beetles

Box elder bugs

Soft Scales & Aphids

Scale on holly

Sawfly Larvae (on rose)

Pecan Phylloxera

Carpenter bees

Galls on oak leaves

Black sooty mold on shrubs

Cellar Spiders in homes

Lots of honey bee calls

Disease Problems

Dogwood spot anthracnose

Large Patch – Turfgrass Diseases: Identification and Control

Leyland Cypress browning

Azalea leaf gall

Oak Leaf Blister

Other Problems

Herbicide damage to tomatoes

Squirrels digging lots of holes in lawns

Contributors

  • Neil Tarver
  • Brian Maddy
  • Louise Estabrook
  • Paula Burke
  • Nathaniel Paul Eason
  • Steve Pettis
  • Michael Wheeler
  • Brenda Jackson
  • Steve Morgan
  • Dr. Elizabeth Little

Oak leaf blister: What is this problem on oak leaves?

Oak leaf blister

Compiled by: Dr. Jean L. Williams-Woodward, UGA Extension Plant Pathology

Oak leaf blister: What is this problem on oak leaves?

Disease Symptoms:
Bulging, blister-like spots on leaves, may cause leaf distortion. Underside of leaf turns brown following spore production. Can be confused with eriophyid mite or midge damage. Affected leaves drop prematurely.

Disease Management:
Disease seldom causes significant damage. Apply fungicide spray when leaf buds swell in the spring and reapply at 7-10 day intervals until the leaf fully expands to reduce disease.

Leaf galls – What is this strange fleshy growth on azalea leaves?

Leaf galls - What is this strange fleshy growth on azalea leaves?
Leaf galls - What is this strange fleshy growth on azalea leaves?
Azalea leaf gall Image by Jean Williams-Woodward, UGA Plant Pathology

Leaf galls

Azalea leaf gall, caused by the fungus Exobasidium vaccinii, are common on azalea in the spring during wet, humid, cooler weather.

The fungus invades expanding leaf and flower buds causing these tissues to swell and become fleshy, bladder-like galls. Initially, the galls are pale green to pinkish. Eventually, they become covered with a whitish mold-like growth. Fungal spores are produced within the white growth and are spread by water-splashing or wind to other expanding leaf or flower buds, or they adhere to newly formed buds, over-winter, and infect these buds the following spring. Older leaves and flowers are immune to infection. As the galls age, they turn brown and hard.

The disease does not cause significant damage to affected plants. It just looks unsightly.

Azalea leaf gall can be prevented in subsequent years by removing the galls by hand as soon as they are detected and destroying them before they turn white and release spores. Fungicides are generally not needed or recommended for control of this disease.

For more information on azaleas, see the UGA publication Selecting and Growing Azaleas.

Watch for and report fungus affecting native azaleas!

Be on the lookout for fungus affecting native azaleas in Georgia


Dr. Marin Brewer at the University of Georgia is working on a fungus that affects Rhododendron canescens, which is commonly known as Piedmont Azalea, Pinxter Azalea, Wild Azalea, Sweet Mountain Azalea, or Wild Honeysuckle. The fungus, known as Exobasidium, forms a flower-shaped gall from the leaves of the azalea. The galls emerge in April and last into the summer.

If you see these flower-shaped galls on azalea in Georgia or have seen them in previous years please contact Dr. Marin Brewer at mtbrewer@uga.edu. We would like to collect them fresh and record their locations. They have been previously spotted in Florida and Alabama.

Dealing with freeze injury to ornamental plants

Jean Williams-Woodward, Extension Plant Pathologist

Freeze injury symptoms can include blackening or bleaching of foliage, tip dieback, stem or branch splitting, and plant death. The damage may not be readily apparent, especially on trees. Trunk damage and splitting may develop months to years later.

Often weak pathogens invade the damaged tissues resulting in trunk and branch cankers (usually from Botryosphaeria spp. infection) and secondary infection by weak pathogens, such as Colletotrichum spp. and Pestalotiopsis spp.

The best approach to deal with freeze injured tissues is to prune off the affected tissues. Prune dead branch tips after bud break. Give plants, such as liriope, a shearing to remove dead foliage.

Freeze on boxwood Woodward

Freeze on cast iron plant Woodward

 

 

 

 

 

 

 

 

 

 

Freeze injury symptoms of bleached, necrotic foliage and split bark (seen at arrows) on boxwood (left), cast-iron plant (upper right) and holly (bottom right). (Images of holly and cast-iron plant by Jean Williams-Woodward; Image of boxwood by Greg Bowman, Gordon County Extension Coordinator)

Rust Fungi in Eastern Red Cedar Trees

Elizabeth Little, UGA Extension Plant Pathologist

Each spring, as the leaves of Rosaceous plants such as apple, pear, and hawthorn are emerging, the Eastern Red Cedar (Juniperus virginiana) produces the bright orange fructifications of a group of rust fungi in the genus Gymnosporangium. Early spring rains induce the cedar rust galls to break hibernation and produce gelatinous orange protrusions that release basidiospores. However, these basidiospores do not re-infect the cedar tree but instead drift off to find the appropriate secondary Rosaceous host (like apple, pear, and hawthorn). On the leaves and/or fruit of the secondary host, the fungus will mate and produce a different type of brightly colored spores. These spores only infect the cedar tree and this infection results in the cedar galls that can take up to two years to mature.

Cedar apple rust
Image 1 – Cedar apple rust (top of image), hawthorn rust and quince rust

The most common and visible cedar rust is cedar-apple rust (G. juniperi-virginianae). Cedar-apple rust forms large round galls on the small branches of the cedar trees. (see image 1) The basidiospores produced by the galls infect the newly emerging leaves of apple and crabapple. On susceptible cultivars, the resulting leaf lesions can cause the leaves to fall during years of heavy infection. Fungicide sprays may help on susceptible trees. However, in the home and/or organic garden, the use of apple cultivars with resistance to both cedar apple rust and fireblight is highly recommended. Removal of cedar trees in the immediate area can help but may not be practical. Check the Georgia Homeowner’s Pest Management Guide for recommended treatments and cultivars.

Two other cedar rusts are common in Georgia, quince rust (G. clavipes) and hawthorn rust (G. globosum). The perennial galls of quince rust are formed under the bark on the cedar branches and are nearly invisible until the gelatinous protrusions emerge from cracks in the bark (see image 1). The spores produced by these galls infect the fruits of the apple, quince, mayhaw, and pear (see image 2). Hawthorn rust produces small inconspicuous galls on the cedar (see image 1). This rust infects the leaves and shoots of ornamental hawthorn.

Quince rust on pear
Image 2 – Quince rust on pear fruit

Why are these annuals dying? What can I do?

Info taken from the UGA publication 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

Color bed disease fig 2 JWW-BPSeasonal color plantings can often appear healthy and beautiful one day and absolutely awful several days later. Total collapse at planting is not uncommon. Even though the chief culprit may be a particular disease, there are usually multiple causes at the root of the problem, all leading to plant demise.

Landscapers can reduce disease pressure in color beds by proper care:

  • Color bed disease fig 2 B JWW-BP
    Figure 2. Mixed planting and improper crop rotation in two consecutive years. The petunias are exhibiting signs of disease in the first year (upper photo) as well as the second year (lower photo).

    Choose plants suited to the sun and light conditions at the site. See this list of annuals with preferred growing conditions.

  • Prepare the soil in the beds to ensure both adequate water retention and drainage by incorporating several inches of organic matter each year.
  • Install annuals at a proper depth to avoid stressing root systems.
  • Remove old materials and spent blooms as much as possible to reduce disease inoculum.
  • Use water sensors on irrigation systems to provide water when it is needed, not on a specific schedule.
  • Choose water delivery methods, such as spray emitters directed at the base of plants, soaker hoses and drip irrigation, that will keep foliage dry.

Avoid planting the same species and cultivar of flowering crop, or crops belonging to the same family, in the same bed for more than two years. For example, petunias should not be followed with petunias because certain pathogens specific to petunias tend to accumulate and persist in the soil from year to year (Figure 2). Additionally, if ornamental tobacco is planted after petunia, it still could lead to plants being attacked by the same pathogens because the crops are closely related. This is of particular concern if the petunias were experiencing problems in the first year, which means that the pathogen is already in the soil and in sufficient quantity to cause damage.

Use the following list to select plants from different families to plant in successive years:

Common annual flowering species and their corresponding botanical family.
Family NameCommon Name of Flowers
AmaranthaceaeCelosia (Spike Celosia, Cockscomb), Alternanthera (Joseph’s Coat)
ApiaceaeParsley
ApocynaceaeVinca (Periwinkle)
AraceaeCaladium, Alocasia, Colocasia (Elephant Ears)
AsteraceaeAster, Marigold, Gazania, Mums, Sunflower, Black-eyed Susan, Echinacea, Zinnia, Mexican Sunflower, Melampodium, Ageratum
BalsaminaceaeImpatiens
BegoniaceaeBegonia
BrassicaceaeAlyssum, Ornamental Cabbage, Kale
CaryophyllaceaeDianthus
CommelinaceaeSetcresea (Purple Heart)
ConvolvulaceaePotato Vine (Ipomoea), Morning Glory
CrassulaceaeSedum
GeraniaceaeGeranium
GoodeniaceaeScaevola (Fan Flower)
LamiaceaeColeus, Salvia, Mints
LythraceaeCuphea (Cigar Plant)
PlantaginaceaeSnapdragon
PoaceaeGrasses (e.g., Pennisetum)
PortulacaceaePortulaca (Purslane)
RubiaceaePentas (Shooting Stars)
ScrophulariaceaeAngelonia (Summer Snapdragon), Torenia (Monkey Flower)
SolanaceaePetunia, Ornamental Tobacco, Ornamental Pepper, Browalia
VerbenaceaeVerbena, Lantana
ViolaceaePansy, Viola

Find more information:

Crop Rotation and Cultural Practices Help Reduce Diseases in Seasonal Color Beds

Flowering Annuals for Georgia Gardens

Flowering Bulbs for Georgia Gardens 

Native Plants for Georgia Part III: Wildflowers

Landscape Plants for Georgia 

Success with Mixed Containers Using Perennial and Woody Plants