Plane Tree Pests Diseases

7/29/2019 Plane Tree Pests Diseases

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Sycamore Diseases & Insect Pests

Of the 10 species of sycamore (Platanus species),one species, American sycamore (Platanusoccidentalis) and one hybrid, London plane tree

(Platanus x acerifolia) are common in SouthCarolina. Both of these trees are well adapted to all

areas of the state; however, they are susceptible to

some diseases and insect pests. As always, the first

line of defense against pest problems is to followrecommended cultural practices in order to maintain

healthy plants. The healthier a plant is, the better it

is able to withstand disease and insect pests. Forinformation on cultural practices that favor the

growth of healthy sycamores, see HGIC 1022,

Sycamore.

Diseases

Anthracnose (Leaf & Twig Blight): Anthracnose

is the most serious disease of American sycamore,

but generally causes only minor damage to theLondon plane tree. It is caused by the fungus

Apiognomonia venata (asexual stage -Discula

platani). This disease may appear as four distinctphases:

1. Twig Blight: This phase occurs in thespring before leaf emergence, killing tips

of small, 1-year-old twigs.2. Bud Blight: This phase occurs in April

and May. The expanding buds die

because of the girdling action of the

canker on the branch.3. Shoot Blight: New shoots and immature

leaves on infected branches suddenly die.4. Leaf Blight: The most characteristic

symptoms are crinkling and browning of

the leaves. Entire leaves may be killedand then fall. These symptoms are very

similar to those caused by late spring

frost injury.

Sycamore anthracnose symptoms on leaves and twigs.

Robert L. Anderson, USDA Forest Service, Bugwood.org

Sycamore anthracnose symptoms on leaf

Clemson University - USDA Cooperative Extension Slide

Series, Bugwood.org

Sycamore anthracnose is favored by cool, wetweather (temperatures under 60 F) during

budbreak and the few weeks of growth that follow.

A severely infected tree may be completelydefoliated (lose all of its leaves) multiple times in a

single season. This defoliation will not kill an

otherwise healthy tree unless it occurs repeatedlyover several years. When a small twig or branch is

affected, cankers may girdle and eventually kill the

branch. The death of a branch will often result in

the production of many small shoots in the area just
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below the girdled portion of the branch, giving that

part of the tree a bushy appearance that is referred

to as witches broom. Spores (reproductivestructures) from the fungus are spread by rain and

wind to healthy leaves, buds and twigs. The fungus

survives the winter on fallen leaves and twigs aswell as on cankers present on twigs that remain on

the tree.

Prevention & Treatment:Apply adequate fertilizerand water to maintain the vigor of the tree(s) as per

recommendations in HGIC 1000, Fertilizing Trees

& Shrubs. When planting a new tree, select acultivar that exhibits resistance. Bloodgood,

Columbia and Liberty (London plane tree

cultivars) are moderately resistant to anthracnose.To limit the number of spores that are present to

start new infections, remove and destroy fallen

leaves and twigs. In addition, prune out and destroy

diseased branches. Care should be taken to disinfectpruning shears in rubbing alcohol or 10% bleach

solution after each pruning cut. For small trees,

spring applications of chlorothalonil, thiophanate-methyl or copper fungicides may protect the tree

from the disease. It is often impractical to spray

large trees. Read and follow all directions on thelabel. For valuable trees, certified arborists can

perform root flare injections using thiabendazole(Arbortect Macro-Infusion Fungicide), which may

aid in tree protection for three years.

Powdery Mildew:Microsphaera species cause

powdery mildew disease on sycamores. This

disease is common on plants growing in shady areas

with high humidity. Powdery mildew typicallybegins as circular or irregular patches of white to

gray powdery material (spores and threadlike

strands of the fungus) on leaves and twigs. Thesepatches may coalesce (grow together) to form a thin

powdery layer on the plant surface. Typically,

young shoots and leaves are more severely affected

than old parts of a tree. Infected leaves becomedistorted, and may turn yellow and drop. New

growth is often stunted. In late summer, small,pinhead-sized black structures may develop on the

whitish gray patches. These structures are for

surviving the winter. The following spring, they

produce a second kind of spore that causes moreinfection.

Prevention & Treatment: For large trees, it isusually not practical to spray, and control is often

not warranted. When spraying is feasible and

necessary, several fungicides (myclobutanil*,

triforine*, thiophanate methyl*, propiconazole,triadimefon, chlorothalonil, sulfur, copper

fungicides, and horticultural oil) are available. Read

and follow all directions on the label.

*Note: Powdery mildew fungi can develop

resistance to these fungicides if they are applied

exclusively.

Bacterial Leaf Scorch: Bacterial leaf scorch (BLS)

is a problem on several species of shade trees,

including American sycamore and Londonplanetree, oaks, maples, sweetgum, dogwood and

American elm. It is caused byXylella fastidiosa, a

bacterial pathogen (disease-causing organism) witha wide host range. This bacterium lives in the host

plants xylem (water-carrying tubes). Many

ornamentals and weeds are hosts to this organism,

but show no disease symptoms. To enter a newplant, the bacteria are generally carried by insects

such as leafhoppers, sharpshooters and spittlebugs

that have fed on xylem fluid from an infected plant.The bacteria may also spread from tree to tree by

root grafts.

Characteristic symptoms of BLS in sycamore

include irregularly shaped areas of scorch (dry andbrown tissue) on leaf margins and between leaf

veins. These symptoms are generally evident in late

summer/early fall. Oftentimes, there will be a bandof reddish color between the scorched portion of the

leaf and the rest of the leaf. Affected leaves may

curl upward, but often remain on the tree.

Sycamore leaves showing the scorched appearance and

upward curling characteristic of BLS.

Edward L. Barnard, Florida Department of Agriculture and

Consumer Services
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Initially, leaves on only one or a few branches may

be affected. With time, symptoms may appear on

other branches of the tree. Symptoms tend to beginwith older leaves on a branch and then develop in

younger leaves. As a result, younger leaves at the

ends of sycamore branches may appear healthy.Over several years, entire branches may die. The

resulting tree decline may require removal of the

infected tree.

Prevention & Treatment: There is no way to

prevent BLS, but if affected limbs are pruned out

early in the infection and well below the scorchedleaves, a cure may be possible. Providing irrigation,

mulch and fertilizer to an infected tree can extend

the life of the tree. Trees with extensive diebackshould be removed and replaced with non-

susceptible trees. Currently, spray treatments are not

available. However, certified arborists can perform

annual root flare injections of antibiotic treatments,using oxytetracycline (such as Bacastat), which can

reduce symptoms by suppressing the pathogen.

Insect Pests

Sycamore Lace Bug: Sycamore lace bug

(Corythucha ciliata) gets its name from the lacy

pattern seen on the adults wings, head, and thorax

(chest region). The adult is small,1/8 inch in length

and brown to black in color.

Sycamore lace bugs.Clemson University - USDA Cooperative Extension Slide

Series, Bugwood.org

Adults survive the winter under peeling bark of the

sycamore tree. They become active in the spring atabout the same time as leaves begin to develop. The

adult female lays eggs on the leafs undersurface,

attaching them with a brown sticky material. In a

few days, the nymphs (immature stage) hatch. The

nymphs are wingless, darker than the adults andcovered with spines. Both adults and nymphs feed

on the undersides of leaves. They have

piercing/sucking mouthparts that they use to removesap from the leaves. Around the feeding sites, the

leaf tissue turns yellow. These yellow flecks are

visible from the leafs upper surface. Late in thesummer, the lower surface of the leaf will typicallybe covered with dark spots of waste material and

the cast off skins of immature lace bugs. Damage to

trees is typically not serious, but heavy infestationscan reduce growth.

Prevention & Treatment:The sycamore lace bughas several natural enemies, including assassin

bugs, minute pirate bugs, lacewings, spiders and

predaceous mites. As much as possible, these

predators should be allowed to reduce lace bugpopulations. To control sycamore lace bugs, it is

important to inspect leaves every week for signs of

the insect. If the tree is small enough, spraying witha strong stream of water can control a light

infestation. Controlling this pest on a large tree

using chemicals is expensive and often notpractical. Since little serious damage results from

lace bug infestation of sycamore trees, toleratingsome damage is a good choice. If insecticide

application becomes necessary and is feasible,

acephate (sprays) and imidacloprid (soil drench) arerecommended for homeowner use. As with all

pesticides, read and follow all label directions and

precautions.

Prepared by Marjan Kluepfel and J. McLeod Scott, HGICInformation Specialists, James H. Blake, Extension Plant Pathologist;and Clyde S. Gorsuch, Extension Entomologist. Revised by J.McLeod Scott, HGIC Horticulture Extension Agent, Clemson

University. (New 01/01. Images added 03/09. Revised 05/09.)

This information is supplied with the understanding that nodiscrimination is intended and no endorsement by the Clemson

University Cooperative Extension Service is implied. Allrecommendations are for South Carolina conditions and may notapply to other areas. Use pesticides only according to the directionson the label. All recommendations for pesticide use are for South

Carolina only and were legal at the time of publication, but the statusof registration and use patterns are subject to change by action ofstate and federal regulatory agencies. Follow all directions,

precautions and restrictions that are listed.

The Clemson University Cooperative Extension Serviceoffers its programs to people of all ages, regardless of race, color, sex, religion, national origin, disability, political beliefs, sexual orientation, marital or family status and is an equal opportunity employer.

Clemson University Cooperating with U.S. Department of Agriculture, South Carolina Counties, Extension Service, Clemson, South Carolina. Issued in Furtherance of Cooperative Extension Work in

Agriculture and Home Economics, Acts of May 8 and June 30, 191 4Public Service Activities

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Plane Tree Pests Diseases