Nina Eckberg

Root Rot on Evergreens

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Source(s): Nina Eckberg

Root Rot on evergreen, is caused by fungi growing in the root system. The fungi include, but are not limited to: Fusarium, Phytophthora, Pythium, Rhizoctonia or Thielaviopsis (Black Rot)

rot

APPEARANCE

Leaves on an evergreen plant turn yellow to orange with no visible signs of insects or fungal disease. The change of color seems to move from the inside of the plant out to the tips. Sometimes exactly half of a plant will turn yellow, as if sprayed with herbicide. The leaves will remain on the plant for extended periods of time.

HOSTS

Azaleas, boxwood, cedars, junipers and rhododendrons.

SEASON

In the summer (during drought) and fall(during planting season), when gardeners over water their plants!

DAMAGE

When the root system of the plant is examined, the roots are black, mushy and slough away in your hand. There may be a swampy smell to the root ball, indicating rotting vegetation.

WHAT TO DO

Do not water plants everyday! Root systems need water and air to survive. Too much water suffocates or drowns the roots, so allow the soil to drain and slightly dry out between watering. Touch the soil around the base of a plant before watering. If the soil is moist, it doesn’t need more water. If the soil is dry, water deeply (at least 1″ of water) and check again in 3-4 days.

Mulch plants with 2-4 inches of mulching material to slow evaporation of water during dry periods. You will water less often if a plant is mulched properly.

If you suspect a root rot, bring a sample to your local Extension Service for proper diagnosis. The Extension Service will recommend a liquid fungicide as needed. READ THE LABEL of the product you choose.

COMMENT

If a root rot effects more than 50% of a plant root system the plant will have a hard time recovering. Fungicide drenches can control the spread of root rot if the disease is diagnosed early.

Resource(s):

Common Landscape Diseases In Georgia

Center Publication Number: 54

Shot-hole Disease

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Source(s): Nina Eckberg

Shot-hole disease is a combination bacterial infection (Xanthomonas prunii) and fungal disease (Blumeriella gaapi and/or Cercospora sp.).

Shot-hole Disease

Shot-hole Disease Identification

Shot-hole disease (on a laurel in the photos) is a combination bacterial infection (Xanthomonas prunii) and fungal diseases (Blumeriella gaapi and/or Cercospora sp.)

Shot-hole Disease Appearance

Circular holes in the leaves that eventually join and make larger holes. The appearance of shooting a shotgun at the shrub and causing multiple holes.

Shot-hole Disease Hosts

Laurels (bay and Otto Luyken), camellia, ligustrum (privets), hydrangea, ivy.

Shot-hole Disease Season

April through October, peak in May and September.

Shot-hole Disease Damage

Leaves appear to be ‘eaten’ away by the disease, leaving a ragged appearance. As leaves are damaged, they begin to fall away, the plant looses its ability to make food and can become stressed.

Shot-hole Disease Integrated Pest Management

Sanitation is the best way to keep the disease from coming back. Clean up contaminated leaves from under the plant. When diseased leaves build-up under the plant, rain or watering can splash the disease back up on the plant. Spray the leaves with Mancozeb, Kocide, Kop-R-Spray or other recommended products containing copper at the first sign of a problem. Always READ THE LABEL and DIRECTIONS FOR USE section carefully when using pesticides.

Resource(s):

Common Landscape Diseases In Georgia

Center Publication Number: 55

Gray Mold or Botrytis Blight on Pansies

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Source(s): Nina Eckberg

Identification of Gray mold or botrytis blight on pansy (Botrytis cinerea).

Gray Mold or Botrytis on Pansies Gray Mold or Botrytis on Pansies

Appearance

Gray to tan spots appear on pansy flower petals following infection. Periods of wet weather and stressful conditions (extreme cold or heat) favor disease development. Leaves and stems of young shoots wilt and die, turning brown to black color. Gray-brown, fuzzy patches (masses of spore) appear, a sign that the gray mold is spreading.

Hosts

Pansy, peony, petunia and geranium are susceptible.

Season

Winter, during wet periods and unfavorable growing conditions.

Damage

Gray mold is an airborne fungus that attacks flowers and damaged or dying tissue. Pansy flower petals discolor and rot. Stems and leaves yellow, then darken, turning slimy. If allowed to spread, the disease will damage the plant.

Integrated Pest Management

Conditions that favor gray mold/botrytis blight are:

  • high rates of fertilization
  • death of lower leaves
  • low light intensity
  • frequent watering
  • crowded plants

If fertilization is done at the time of planting and supplemented once a month, the plant stress will be less. Remove dead lower leaves so the disease has no food source. Be sure the planting bed is in a sunny area. Allow plants to dry out between waterings. As plants mature and fill the flowerbed, remove plants that are too close together. All of these conditions will stimulate healthy pansy growth without disease.

Comment

If you think you have gray mold/botrytis blight in your pansies, bring a sample to the Extension office for diagnosis.

Resource(s): Common Landscape Diseases In Georgia

Center Publication Number: 59

Black Spot on Roses

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Source(s):Nina Eckberg

Identification of Black spot on roses.

black spot

Appearance

Black spots 2-12mm in diameter develop on upper leaf surfaces. Leaf tissue surrounding the spots turns yellow and the yellowing extends throughout the leaf. On resistant roses, only tiny black flecks may form and leaves remain green. Raised, purple-red blotches develop on immature wood of first-year canes of susceptible roses.

Hosts

Rose varieties such as teas, hybrid teas, briers and polyanthas are quite susceptible. Rugosa, moss roses and wichuraianas are more resistant to the disease.
SEASON:Leaves are most susceptible while still expanding (6-14 days old). Fungal spores must be immersed in water and continuously wet for at least 7 hours while temperatures are between 70º-80º F.

Damage

When black spot is on a plant, the leaves can begin to fall off. Some plants become completely defoliated, but if cared for,will survive. Black spot lesions on the rose canes are small and seldom kill the plant, but are important in the survival of the disease over the winter.

Integrated Pest Management

Several steps can help control black spot on roses:

  • Air circulation around bushes speeds up drying and reduces black spot.
  • If possible, do not water plants overhead with sprinklers. Leaves must not be allowed to remain wet or in high humdity for more than 7-12 hours.
  • Sanitation is extremely important in controlling black spot. Remove leaves from the ground and prune canes that have lesions to reduce overwintering of the disease.
  • Fungal sprays can be used during periods of the year when conditions are favorable for black spot. Preventive spraying can begin in March until leaves are mature, then spray fungicide as needed. Call the Extension Office for the type of fungicides that control black spot and remember, READ THE LABEL of the product you choose.

Comment

If you think you have black spot on your roses, bring in a plant sample to the Extension Office for diagnosis.

Resource(s): Common Landscape Diseases In Georgia

Center Publication Number: 57