Common Tree Problems in Atlanta
Oak Leaf Blister
Taphrina caerulescens
Symptoms:
Oak leaves begin to show chlorotic, blister-like areas
on the upper surface that can be as large as one half
inch in diameter. The lower surface
has gray depressions that correspond to the raised
blisters. As the disease progresses, the blisters turn
brown and the leaf will curl as the blisters coalesce.
Premature leaf drop also may occur. Trees are not
severely damaged, but the appearance of the tree may
be unsightly. All oak species are susceptible to this
disease.
Favorable Conditions:
Leaves become infected when buds are beginning to
open in the spring. The pathogen can survive winter
on plant twigs and bud scales. The disease develops
during wet, humid, mild conditions in the spring.
Spores causing oak leaf blister are spread by wind and
rain.
Control:
Rake fallen leaves and debris and discard to reduce
disease inoculum. Contact Atlanta Arbor Care to treat with a fungicide.
Anthracnose
Apiognomonia quercinia
Symptoms:
Symptoms vary with host, weather and time of infection. Shoot blight is one of the first symptoms seen in
spring. Blighting causes leaves and shoots to brown
and shrivel. Young leaves become cupped or distorted
with necrotic lesions. Large lesions often follow leaf
veins or are delimited by leaf veins. Old lesions are papery and gray to white in color.
On the underside of an infected leaf, tiny brown fungal
fruiting bodies may be visible on or near major veins.
Premature leaf drop is common. Mature leaves are
fairly resistant and the symptoms are simple necrotic
spots. If infection is severe, branch cankers and twig
dieback can occur during winter and early spring. The
symptoms usually first appear on lower branches and
then spread upward. Favorable Conditions:
Anthracnose fungi overwinter in twigs and plant debris. If winters are mild, the pathogen is active causing cankers and dieback. Spores are spread by wind
and rain during the spring and infect new shoots. This
disease can have multiple cycles per year if the weather is moderately warm and wet.
Control:
Rake and destroy fallen leaves. Call Atlanta Arbor Care to prune lower branches
to increase air circulation and ensure proper tree fertility and irrigation. Chemical controls are rarely recommended unless trees are newly established.
Tubakia Leaf Spot
Tubakia dryina
Symptoms:
The symptoms caused by Tubakia are brown or reddish brown blotches on the leaves. Premature leaf
drop and twig cankers are common if the trees are
severely infected. Spots are well-defined on young
leaves and enlarge to necrotic blotches on older leaves. Small fungal fruiting bodies can be
seen within the lesions. Lesions may cause leaves to
collapse if they are on veins and restrict water movement.
Favorable Conditions:
The disease overwinters on twigs and plant debris. It
favors wet, humid conditions and warm temperatures.
Primary spore dissemination is by wind and rain. Red
oaks are more susceptible than white oaks.
Control:
Rake and dispose of fallen leaves. Call Atlanta Arbor Care to prune trees to
increase air circulation and ensure proper fertility and irrigation.
Bacterial Leaf Scorch
Xylella fastidiosa
Symptoms:
Symptoms of bacterial leaf scorch are described as
marginal leaf burn and are very similar to drought
stress symptoms (Fig. 7). In addition to marginal leaf
burn, there is a defined reddish or yellow border separating the necrosis from green tissue. Symptoms are
more noticeable in late summer after hot, dry conditions, but symptoms can be expressed all year. Symptoms first appear on one branch or section of branches
and on the oldest leaves. Each year symptoms will
reoccur and progress to other parts of the tree.
Favorable Conditions:
The disease is spread by leafhoppers, spittlebugs and
through root contact with neighboring trees. Since the
pathogen is harbored within insects, warm temperatures and high populations of leafhoppers and spittlebugs are conducive for bacterial leaf scorch.
Control:
Call Atlanta Arbor Care to remove severely infected trees and replant using
resistant species. Control weeds (to minimize insect
populations) and ensure proper tree fertility and irrigation to maintain health and vigor.
Hypoxylon Canker
Hypoxylon spp.
Symptoms:
Yellowing and wilting of leaves often related to physiological stress may be the first symptom of this disease. Fungal mats (stroma) will develop beneath the
bark of infected trees. Bark will begin to slough-off
due to pressure from the stroma beneath it. Stroma exposed by sloughing bark is hard, tan to silver gray on
the outside, and black within. There
may be small patches to elongated strips. Old stroma
eventually loses the gray color and appears black. The
sapwood becomes tan to light brown and has a definite
black border.
Favorable Conditions:
Hypoxylon cankers are opportunists that attack trees
weaken by other factors such as heat, drought, wound,
root injury or other diseases. Oak species most commonly infected are black, blackjack, laurel, live, post,
and white oaks. Hypoxylon can be present as a latent
colonist in healthy trees and this may account for the
rapid invasion of stressed trees. The fungus is favored
by warm temperatures of 60 to 100 degrees F but the
optimal temperature is near 86 degrees F. Spores are
primarily wind dispersed.
Control: Call Atlanta Arbor Care to keep trees vigorous with proper fertility and irrigation. Prevent wounds from mechanical, weather and
insect injury. Remove infected limbs or trees once
they become hazardous to property or people, and to
reduce disease spread to adjacent trees.
Bacterial Wetwood
Symptoms:
A sour odor is often associated with wetwood as water-soaked wood with large numbers of dead bacteria
begin to break down. The build-up of bacterial populations within the tree causes fermentation resulting in
internal gas pressure of up to sixty pounds per square
inch. Foliage sometimes wilts and branches may dieback. However, most of the time, wetwood is a minor
problem that leaves a vertical streak on the bark where
pressurized liquid escaped out of wounds. Many times, secondary fungi and bacteria
infect the surface liquid and create a slimy texture on
the bark.
Favorable Conditions:
Bacteria that cause wetwood tolerate low oxygen and
are often found in soils and on plant surfaces. Bacteria enter through assorted wounds above and below
the soil line. The bacteria may lay dormant during
the greatest periods of growth and become active in
mature or older tissues.
Control:
The only known controls for bacterial wetwood are a bactericide that can only be applied by Certified Arborists and
a 10% bleach solution which anyone may apply to
clean stains off the bark and reduce the smell.
Armillaria Root Rot
Armillaria spp.
Symptoms:
There are several general symptoms that accompany
Armillaria root disease, including crown dieback,
growth reduction, premature leaf drop or death of the
tree. Because these fungi commonly inhabit roots,
their detection is difficult unless characteristic mushrooms are produced at the base of the tree. Removing
the bark will expose the characteristic, white mycelial
rhizomorphs that grow between the wood and the
bark. Short-lived mushrooms may be found
growing in clusters around the bases of infected trees.
They are honey brown to reddish in color.
The fungus breaks down lignin and cellulose causing
the wood to become spongy.
Favorable Conditions:
Spread occurs when rhizomorphs contact uninfected
roots. Rhizomorphs can grow for distances of up to
ten feet and penetrate the roots by a combination of
mechanical pressure and enzymatic action. Mushrooms are produced in late summer or autumn, and are
most abundant during moist periods.
Vigorously growing trees often confine the fungi to
localized lesions and limit their spread up the roots
by secreting resin and rapidly forming callus tissues.
But when infected trees are in a weakened condition,
Armillaria spreads rapidly through the roots.
Control:
Because these fungi are indigenous to many areas and
live on a wide variety of plants and woody material,
their eradication is not feasible. Management should
be directed toward increasing tree vigor by calling Atlanta Arbor Care to
insure proper irrigation and fertility.