Tree and Forest Health Guide

Introduction
Much of forestry involves promoting and protecting the health of selected trees. This manual is intended to help Virginia foresters provide good advice about tree and forest health to landowners. It is not a substitute for the many excellent references that help identify and treat specific pest problems. Detailed information is limited to conditions that are common or important enough in Virginia to gain frequent attention. General guidelines are also given for the diagnosis and treatment of less familiar conditions.

Health is an abstract concept and has no definition that applies universally. Tree health is quite different from forest health. Generally speaking, a tree is considered healthy if it exhibits no symptoms or signs of injury or disease. Beyond this there is no commonly accepted basis for characterizing tree health. It is meaningless to ask how healthy a tree is. In reality, what we usually address is not health, but "sickness" because it is more concrete and we have some experience in dealing with it.

Forest health usually refers to the biological and environmental functions of forests, relative to human wants and needs. Perspectives vary, but the ideas of diversity and sustainability are common to most definitions. Dead and unhealthy trees are natural components of healthy forests.

This primer attempts to address both health and sickness as they apply to managing the private forests of Virginia.

"Fiber farming," the highly intensive production of wood to the exclusion of other objectives, is more akin to traditional agriculture, and involves unique circumstances that are outside the realm of this manual.

Although the following information applies to urban areas, it does not include some unique problems that result from the highly disturbed and altered conditions or the prevalence of non-indigenous species that characterize urban environments.

Guidelines for Promoting Tree and Forest Health

The following generalities should be considered when making management recommendations; but they are only guidelines, not rules:

1. Tree species tend to survive and grow best within their natural ranges; artificially extending these ranges involves risk. Occasionally it's worth the risk; many species perform well even on foreign continents. Experience is the only reliable guide. Trees do not always grow best on the sites where they normally occur; they just compete best in those places. When competition is not a factor, most species tend to grow best on deep, moist, well drained, fertile soils.

2. If management objectives don't require pure stands, encourage species mixes. Mixed stands tend to be less susceptible to attack and less vulnerable to damage from pest organisms.

3. It is the crown that uses light energy to produce cellulose (a complex carbohydrate) from carbon, hydrogen and oxygen; roots only provide water and nutrients to support the process. A full crown is necessary for optimum health and growth; give crowns all the light they can use. This will also ensure that roots have adequate space.

4. Trees usually respond quite slowly to environmental changes. They may decline over a period of several years before succumbing to prolonged stress; and it may take many years of favorable conditions before they recover fully from a weakened state. A tree's apparent health does not always reflect current conditions.

5. Injuries to boles and branches often lead to defect, degrade and decline, particularly among hardwoods. Thinnings and other partial cuts should be planned so that injuries are minimized and damaged trees can be removed as cutting progresses. This usually means beginning in the least accessible parts of a tract.

6. Roots are damaged by soil compaction, grade change and mechanical injuries. Expect tree decline and mortality following significant soil disturbance. Design access for partial cuts and construction sites so that soil disturbance is minimized around residual trees.

7. Vigor decreases with advanced age; trees can live longer than people, but they don't live forever. Harvest trees when they mature, or expect them to deteriorate.

8. Well designed and properly constructed roads help ensure long term forest health; they only have to be installed once, they help protect trees against injury, they protect water quality and they minimize site degradation from management activities.

9. Unusual habitats tend to include species and environmental conditions that can be difficult to reestablish if lost. Protection of these areas from disturbance is often an easy and effective way to help maintain or enhance diversity.

Diagnosing Tree Problems

When the cause of a health problem is not obvious there are always clues that can help with diagnosis. It is naive, however, to expect a satisfactory explanation for every condition. Many, if not most, tree problems result from combinations of factors. Often some abiotic (nonliving) influence, such as drought, makes trees more susceptible to invasion by biotic (living) agents such as fungi and insects. Fortunately, good advice does not always rest on complete understanding. The following tips should lead toward good advice.

1. Problems caused by physical, chemical and environmental factors usually affect most or all plant species present, whereas problems caused by organisms seldom affect more than a few species, and often just one.

2. Symptoms caused by organisms usually vary in space and develop over time; symptoms that appear suddenly, are relatively uniform and stabilize quickly, are probably not caused by an organism.

3. Healthy buds support a prognosis of recovery; dead or unhealthy buds suggest that recovery is unlikely.

4. Wilting indicates that water is not moving through the tree fast enough. The most common causes of wilting are root disease, vascular disease and drought. Vascular disease is usually caused by microorganisms; root disease can stem from physical or chemical injury, excess moisture, infection by microorganisms, and feeding by various animals.

5. Symptoms often result from the effects of secondary agents, not the primary agent. Trees weakened by adverse weather, unfavorable site conditions, injury, competition or advanced age become more susceptible to infections and infestations by secondary organisms. Treatment related to these secondary agents will provide temporary benefits at best, unless the primary problem is also addressed.

6. Agents that affect only foliage are unlikely, in themselves, to result in tree mortality; but they can reduce growth and predispose trees to other problems. Agents that affect only heartwood (e.g., some decay fungi) can increase the likelihood of stem breakage, and can make trees unmerchantable, but they might have little effect on tree life span.

7. Symptoms that seem to be associated with aspect, exposure, drainage or disturbance are very likely to involve an important environmental component; but organisms could still be the primary agent(s).

8. Check with a hand lens before ruling out organisms. Look for frass, silk, eggs, shed skins, holes, or life stages of mites and small insects. If you suspect fungus infection look for fruiting bodies, lesions, cankers, resin or sap flow, resin soaking of stems or roots, or sapwood stain near the transition between healthy and diseased tissue.

9. Genetic factors can have a noticeable effect on tree response to adverse conditions. Symptoms of ozone injury and needle cast infection, for example, can vary greatly among trees of the same species growing right next to each other.

Making Recommendations

Although the potential causes of tree problems are countless and complex, practical treatment options are relatively limited and simple. You can often provide good advice without specific and detailed knowledge about causal agents. The following guidelines should help you evaluate what is practical to do in most cases.

Landowners expect foresters to know something about yard trees as well as forest trees. In both cases, good advice hinges on knowing ownership objectives. Yard trees present such different circumstances from forests that they will be discussed separately.

Yard Trees

Trees in yards are usually valued for beauty, shade, screening, wildlife habitat, fruit, real estate enhancement or some combination of these. What matters most are appearance and expected life span; defect and degrade are often unimportant except when they create unacceptable hazards.

Regardless of the cause or nature of yard tree problems, there are only a few practical treatment alternatives available to most homeowners: mulching, fertilization, sanitation, watering and pesticide application. Often the appropriate treatment(s) can be chosen without specific information about causal agents. Yard tree problems resulting from environmental stress or moderate site disturbance can usually be alleviated by improving soil conditions. Even healthy trees benefit from attention to soil quality. Important soil characteristics include aeration, moisture retention, fertility and drainage. The simplest way to improve and maintain soil characteristics is through mulching. Apply a layer roughly two inches thick over as large an area as suits the landscaping scheme. This also helps reduce injuries from lawnmowers and other equipment. Organic mulch is preferable; avoid piling it against the bole. Where soil compaction is already severe, aerate before mulching. Watering during drought helps, but is often impractical except for small trees and new transplants because of the large volumes required; occasional thorough soaking is best. Nitrogen fertilization is usually beneficial for trees in decline. Avoid changing grade level or drainage characteristics around established trees. Select species adapted to poorly drained soils or install drainage and condition the soil before planting in wet areas.

Yard tree problems resulting from infestation or infection by organisms can sometimes be ignored or reduced through sanitation. Removal of dead, dying or fallen twigs and foliage is usually harmless and often helpful. When removing infected twigs, cut well back into healthy tissue; sanitize pruning instruments between cuts if transmission of microorganisms is likely. Use of registered pesticides should be considered only after the landowner is aware of alternatives, consequences, costs and benefits and when unacceptable damage can be prevented through pesticide application. For large trees, pesticide applications should be left to companies that have the specialized knowledge and equipment required for such treatments. The cost per tree is usually high.

Forest Trees

Private forests are usually valued for recreation (including wildlife benefits), screening, environmental protection, income, investment, financial reserve, inheritance or some combination of these. High timber value is an asset even when it is not an ownership objective.

The benefits of preventing or treating forest tree problems depend largely on the perspective and disposition of the landowner. Prevention through proper thinning, sanitation and protection is usually most practical. Heed these tenets to establish and maintain healthy forests: match species to site, favor species mixes where practical, protect unusual habitats, give desired trees plenty of light and growing space, prevent or avoid unnecessary site disturbance and tree injury, remove undesirable trees, harvest trees before their quality begins to decline. Pesticide applications and other special treatments are expensive and should be subjected to cost/benefit analysis. Sometimes, the value of a single, high quality tree is enough to cover the management costs for several acres.

Tree Problems: Diagnosis and Treatment

1. Several to many unrelated species affected

1. Only a few or related species, or only a single tree affected

2.(1) Signs of feeding or oviposition present: generalist feeders such as gypsy moth, fall cankerworms, sapsuckers, beaver and deer; oviposition injury by cicadas; small area clearing by woodchucks or mound ants. Defoliation of healthy trees can usually be ignored; protection of unhealthy trees, if desirable, should be accomplished before significant feeding has occurred. Appropriate barriers can protect individual trees against birds, mammals and cicadas.

2.(1) No such signs: weather damage; air pollution; chemical injury; site disturbance; fire; flooding. Such conditions are usually beyond practical treatment; trees often recover on their own.

3.(1) Symptoms relatively uniform within tree and among trees so that affected parts (or whole tree) look very much the same wherever they occur.

3.(1) Symptoms vary within or among trees and may change or progress noticeably over a period of a few to many days.

4.(3) Whole tree involved to some extent (i.e., dead, discolored, wilted, missing, debarked).

4.(3) Some tissues or parts of tissues not involved: chemical injury; air pollution; heat or cold injury; lightning, hail or squirrel injury; some insects, mites or microorganisms. Such conditions are usually beyond practical treatment; see section on common and important problems.

5.(4) No above ground evidence of biotic agents; some foliage or twig distortion possible: herbicide, salt or other chemical poisoning; root problem from infection by microorganisms, site disturbance, flooding, girdling by insects or mammals, drought, transplanting shock, shallow soil, winter injury or suppression; vascular disease from microorganisms, including nematodes; storm damage; lightning. Such conditions are usually beyond practical treatment; see section on common and important problems.

5.(4) Above ground symptoms of infestation, infection or other injury present: mammal damage; bark beetles; severe foliage injury or defoliation by caterpillars, mites, lacebugs, miners, beetles, scales or fungi. Sanitation often helps; pest suppression is sometimes appropriate; see section on common and important problems.

6.(3) Symptoms include one or more of the following: feeding injury, frass, silk, galleries, holes, shed skins, waxy secretions, honeydew, galls, slits, stage of causal agent (use hand lens; dissect galls, affected twigs, bark): insects, mites, mammals, birds. Pest suppression is sometimes appropriate on Christmas trees and ornamentals, especially for scale insects and mites.

6.(3) Symptoms include one or more of the following: cracks, lesions, stains, fruiting bodies, resin flow, cankers, galls, leaf spots or blisters, scorch, bleaching, browning, premature abscission, chlorosis, mottling, epicormic sprouting, necrosis, decay: microorganisms, weather, soil conditions. Sanitation often helps; see section on common and important problems.

Tree Problems: Common and Important

Pests or conditions that affect many host species are listed only under the most common host(s)

Conifers

Eastern Hemlock

Pest or Condition: woolly adelgid
Evidence: white, cottony masses on undersides of branches, especially Feb.-May
Effect: gradual discoloration followed by defoliation, decline, mortality
Notes: treat valuable yard trees with horticultural oil, insecticidal soap or systemic insecticide

Pest or Condition: spider mites
Evidence: older foliage turns gray-green, drops; newer foliage stippled near center
Effect: defoliation, vigor loss
Notes: common in yard trees; use hand lens to see fine silk, eggs, adults or strike branch over white surface to dislodge mites; treat ornamentals with miticide as soon as infestation evident

Pest or Condition: drought
Evidence: decline, mortality; hemlock borer infestations following drought
Effect: usually fairly synchronous regional decline and mortality
Notes: most mortality often along stream banks

Eastern Redcedar

Pest or Condition: cedar-apple rust
Evidence: orange, gelatinous fruiting structure in spring, dries to woody gall
Effect: sometimes kills portion of twig beyond gall
Notes: can cause significant disease on alternate host apple trees

Pest or Condition: bagworm
Evidence: tough, silk-and-needle bags hanging from host foliage; defoliation
Effect: defoliation can be severe and repeated, often ruins yard trees
Notes: control by removing, disposing of bags if practical; chemical suppression
should be applied early, when bags are very small; feeds on many species

Pest or Condition: annosum root rot (see yellow pines)

Pest or Condition: Phomopsis blight
Evidence: dead branch tips with grayish band at base where fruiting bodies occur
Effect: can kill seedlings; may invade stem and cause canker
Notes: common in nurseries, yard trees; affects succulent tissues; dead tips persist

Eastern White Pine

Pest or Condition: white pine weevil
Evidence: wilted/dead/infested terminal
Effect: kills tree top only; also infests Norway spruce
Notes: spray Christmas tree plantation in late March if 5% or more trees infested the previous year; prune out infested terminals in June before weevils exit; tie side branch in upright position if height growth and form are important

Pest or Condition: procerum root disease
Evidence: chlorosis, wilting, resinosus on bole, basal canker, blue-black basal sapwood stain (one or all in any combination)

Effect: kills tree
Notes: uncommon in natural stands; remove infected tree and roots where practical; do not replace with another white pine; do not plant white pine in poorly drained soils

Pest or condition: pine bark adelgid
Evidence: bole with light to heavy white, cottony covering
Effect: prolonged infestation can be associated with bark disease, tree mortality
Notes: natural controls usually effective; can be suppressed with insecticides

Pest or condition: white pine blister rust
Evidence: branch/bole cankers with orange fruiting bodies in spring
Effect: stem deformity; eventual mortality
Notes: almost exclusively west of Blue Ridge; significant problem only in high hazard areas; conduct preplanting exam to locate and eliminate alternate host plants (i.e. currants and gooseberries, genus Ribes)

Pest or Condition: introduced pine sawfly
Evidence: larvae; defoliation from up to three generations; cocoons on vegetation
Effect: eventually consume both old and new needles; reduce growth
Notes: only sawfly on white pine that spins cocoon above ground; natural enemies usually prevent extended outbreaks

Pest or condition: Pityogenes hopkinsi (bark beetle)
Evidence: tiny, frass-filled entrance holes in smooth bark of stem or branches
Effect: portends tree mortality
Notes: infests slash or trees weakened by other agents

Pest or condition: eriophyid mites
Evidence: small portion to whole crown gradually turns off-green to yellowish
Effect: needle loss; weakens tree
Notes: cigar-shaped mites too small to see without hand lens and good light, look between needles near base; symptoms progress quickly; infested Christmas trees should be treated immediately

Pest or Condition: white pine aphid
Evidence: shiny, dark aphid with white dorsal stripe; rows of dark eggs on needles
Effect: heavy infestations can reduce growth of individual branches, small trees
Notes: hatching eggs can be nuisance on Christmas trees

Pest or condition: ozone injury
Evidence: tip to most of needle light yellow
Effect: probable growth reduction
Notes: sharp transition between affected tip and unaffected base of needle; small percentage of trees
exhibit symptoms owing to genetic predisposition

Pest or Condition: deicing salt injury
Evidence: roadside foliage scorch, defoliation, dieback, decline
Effect: repeated application and gradual accumulation can lead to mortality
Notes: injury occurs both through soil and foliage contact with splashed water or salt in blown roadside
dust; tolerance to salt varies greatly among species

Pest or condition: adverse site
Evidence: poor growth, thin crown, chlorosis
Effect: low vigor, unhealthy appearance, mortality
Notes: white pine has been planted as an ornamental or screen in many places where it does not occur naturally;
sometimes it does well in such places but it should not be planted in poorly drained soils or in the hottest and
driest regions of Virginia

Pest or condition: physiological needle blights
Evidence: orange to reddish-brown tips on newest foliage; or yellowing and shedding of older needles especially
in top third of tree; buds healthy
Effect: no lasting effect on otherwise healthy trees
Notes: devalues Christmas trees; weather related, no treatment available

Fraser Fir

Pest or condition: Phytophthora root rot
Evidence: foliage turns brown; can be more gradual on larger trees
Effect: tree mortality
Notes: avoid planting in poorly drained soils; spreads readily through infected soil

Pest or condition: balsam twig aphid
Evidence: needles twist, particularly on branch tips, to reveal silvery undersurface
Effect: alters tree appearance; heavy infestations can stunt growth
Notes: infested Christmas trees should be sprayed when buds swelling in spring

Pest or condition: balsam woolly adelgid
Evidence: top growth stops; gouty branch swellings; white flocculence on bole
Effect: tree decline and mortality
Notes: individual trees can be protected with thorough spray coverage

Pest or condition: eriophyid bud mites
Evidence: buds enlarge and flatten out
Effect: stops branch growth
Notes: treat when buds swell in spring

Pest or condition: spider mites
Evidence: older needles gradually lose healthy color; mites, silk visible with lens
Effect: heavy infestations can cause needle drop
Notes: treat when mites present on significant percentage of foliage

Pest or condition: freeze injury
Evidence: new growth, young cones turn brown; succulent shoots droop
Effect: growth loss
Notes: avoid planting in frost pockets

Southern Yellow Pines

Pest or Condition: regeneration weevils
Evidence: chewed/girdled stem/twig on small trees/branches in spring and fall
Effect: kills or weakens seedlings; can cause branch flagging on larger trees
Notes: plant insecticide treated trees when reforesting harvested area that was
10% or more pine and was cut or site prepared after May, or spray seedlings
after planting, or delay planting for one full growing season; feeding injury can
be under ground; affects all pine species

Pest or condition: bark beetles (southern pine, turpentine, Ips)
Evidence: pitch tubes, galleries, fading crowns, fallen frass, fallen green needles
Effect: tree mortality from successful attacks; sometimes only top kill from Ips
Notes: periodic southern pine beetle outbreaks cause severe local to regional
pine mortality; turpentine beetles usually attack injured or weak trees, low density
attacks sometimes don't kill tree; Ips beetles tend to attack only stressed trees; all pines affected

Pest or Condition: Nantucket pine tip moth
Evidence: dead, resinous buds, branch tips
Effect: delayed growth of affected branch or terminal; temporary deformity
Notes: problem mostly for small trees; multiple generations; tends to be more severe where site preparation intensive

Pest or condition: pine webworm
Evidence: frass-filled, silk webbing on top or entire seedling; defoliation
Effect: weakens tree, retards growth; can contribute to seedling mortality
Notes: very common, particularly in first growing season; no practical control

Pest or condition: annosum root rot
Evidence: poor growth and color; eventual mortality, increasing over time; small,
rough, irregular conk at ground line; resin soaking of infected roots; also kills eastern redcedar if present
Effect: gradual mortality, spreads to neighboring trees through root grafts, stumps
Notes: severe only in deep, well drained sands; do not thin heavily infected stands on high hazard sites,
harvest when practical

Pest or condition: stem rusts
Evidence: globular or spindle shaped swelling on branch; canker on bole
Effect: stem deformity; can result in mortality of portions beyond, above infection
Notes: minor economic importance in Virginia; rust fungi have alternate hosts

Pest or condition: pitch canker
Evidence: branch, bole canker with resin flow; wood resin-soaked; shoot dieback
Effect: dieback, deformity, poor growth; sometimes eventual mortality
Notes: top dieback common symptom on loblolly; avoid branch and bole injuries

Pest or condition: Atropellis canker and Diplodia blight
Evidence: small, resinous branch or stem cankers; wood resin-soaked/dark stained
Effect: dieback or deformity
Notes: can be separated from pitch canker by dark staining of wood; common
problems on Scotch pine Christmas trees; can be spread by shearing

Pest or condition: needle cast
Evidence: older foliage turns some shade of yellow to brown or gray-brown; often
mottled or banded; dark fruiting bodies sometimes evident

Effect: discoloration, early loss of older needles
Notes: occasionally prevalent over large area; much individual tree variability;
many species of fungi cause needle cast; Christmas and ornamental trees
can be protected by fungicides

Pest or condition: sawflies
Evidence: spring defoliation of older needles on branch to whole tree
Effect: growth reduction; rarely mortality
Notes: larvae (several species) feed gregariously; periodic, large population
fluctuations; tend to occur in patches rather than uniformly over region;
many natural control agents usually effective

Pest or Condition: eastern pine looper
Evidence: ash-gray moths in understory in May and June; larvae feed into late fall
Effect: defoliation, growth reduction of loblolly pine
Notes: most prevalent in coastal plain, occasionally at high population densities

Pest or Condition: pine spittlebug
Evidence: spittle mass with immature bug inside
Effect: can enable invasion of fungi
Notes: adults feed on same hosts, but don't produce spittle

Pest or condition: voles
Evidence: small trees turn from yellow to brown; feeding injury evident at base
Effect: usually tree mortality
Notes: feeding sometimes below ground; usually associated with snow cover;
worse where sod, other vegetation dense; can be partially prevented by
keeping sod killed/mowed back

Spruces

Pest or Condition: spider mites
Evidence: foliage turns off-green, then yellow to brown and eventually drops,
from bottom up and inside out; eggs, mites, silk visible with hand lens

Effect: Gradual defoliation, can lead to mortality
Notes: Favored by cool, dry weather; particularly common on Alberta spruce;
treat with miticide, horticultural oil when discovered

Pest or Condition: adelgid twig galls
Evidence: pineapple shaped swellings on twigs
Effect: disfigures ornamentals
Notes: more than one species; adults, eggs near bud bases; can suppress with
dormant oil spray

Pest or Condition: white pine weevil on Norway spruce - see eastern white pine

Pest or Condition: adverse climate/weather
Evidence: poor growth and color, infection and infestation by secondary agents
Effect: transplanting failure; poor growth; mortality
Notes: many places in Virginia are too hot and dry for spruces to remain healthy

Hardwoods

Ash

Pest or Condition: borers
Evidence: galleries; exit holes; sap, frass associated with entrance hole
Effect: wood product degrade; weakening, mortality of ornamentals
Notes: avoid injuries; fell brood trees; process sawlogs promptly

Pest or Condition: ash yellows
Evidence: basal witches broom, growth decline, thin crown, bark cracks, mortality
Effect: pronounced growth reduction, eventual mortality
Notes: harvest infected forest trees; fertilize infected yard trees

Beech

Pest or Condition: beech bark disease
Evidence: red, lemon-shaped fruiting bodies visible with hand lens; tiny, white scale
infested bark; rough, dead bark patches

Effect: gradual decline, invasion by secondary organisms, breakage and mortality
Notes: infections by nectria fungi follow scale infestation and kill areas of bark;
trees can be girdled or may live many years, but continue to deteriorate; some trees are resistant to the scale

Pest or Condition: beech blight aphid
Evidence: aphids covered with long, white cottony threads on branches, bark
Effect: occasional high populations result in profuse honeydew, sooty mold
Notes: common on forest trees; little effect

Cherry

Pest or Condition: eastern tent caterpillar
Evidence: silk webs in branch crotches; larvae
Effect: defoliation in early spring
Notes: common on roadside cherry and home fruit trees; natural enemies
eventually suppress high populations; shiny, dark, cylindrical egg masses
around small twigs can be removed to achieve control

Pest or Condition: cherry scallop shell moth
Evidence: leaves webbed together on branch ends with larvae inside
Effect: defoliation, sometimes complete
Notes: usually regulated by natural enemies; mostly on black cherry

Pest or Condition: black knot
Evidence: rough, black elongate branch galls
Effect: progressive branch dieback
Notes: prune out and remove infected branches before early spring

Dogwood

Pest or Condition: dogwood anthracnose
Evidence: tan, purple rimmed leaf spots, brown blotches and margins; starts in
lower crown; dead leaves often persit

Effect: tree mortality
Notes: mostly a problem at altitudes above 1000 feet and in moist conditions;
confirmation requires lab culture; prune water sprouts to reduce infection;
spot anthracnose, leaf spot very common on dogwoods and not serious

Pest or Condition: borers
Evidence: withering leaves, twig dieback, sunken bark, basal wounds
Effect: dead twigs; decline; sometimes mortality
Notes: twig borer larva kills only small stems, can be pruned out; main stem borer
usually gains entry through wounds, larvae feed on cambium and can girdle tree;
protect trees against lawnmowers, string trimmers

Pest or Condition: club gall
Evidence: swellings on small twigs
Effect: some tip dieback
Notes: very common, caused by a midge (gnat-like fly)

Pest or Condition: powdery mildew
Evidence: bright white to grayish patches or complete covering of leaf surface
Effect: distortion, discoloration of developing and developed leaves
Notes: weather related; suppression not necessary; don't fertilize while infected

Elm

Pest or Condition: vascular diseases
Evidence: wilting, yellowing of foliage; sapwood stain
Effect: branch dieback, mortality
Notes: Dutch elm disease can be prevented and treated through sanitation and
fungicidal injection; it can be confirmed through culture; no treatment is available for elm yellows

Pest or Condition: leaf beetles
Evidence: skeletonizing; larvae
Effect: heavy defoliation, nuisance from descending larvae
Notes: several species; elm leaf and larger elm leaf beetles noticed most in yards

Hickories

Pest or Condition: decline
Evidence: premature leaf coloration; progressive dieback; attacks of secondary
organisms

Effect: decline over several years, often leading to mortality
Notes: episodes have been associated with drought, shallow soils, shoostring root
rot, bark beetles and borers; and with disturbance from construction; borer infested trees
should be felled or removed when practical

Pest or Condition: gall phylloxera
Evidence: spherical galls on twigs and leaf stems
Effect: sometimes severe infestations result in early leaf fall
Notes: many species of phylloxerans on hickories; only a problem on yard trees

Pest or Condition: fall webworm
Evidence: gregarious larvae inside increasingly large webs covering foliage
Effect: defoliation, sometimes complete
Notes: infests many tree species; often prefers hickories; periodically at outbreak densities along Blue Ridge

Pest or Condition: twig girdlers/pruners
Evidence: smoothly severed branches; may have central gallery
Effect: clutter of fallen branches; foliage, twig loss; crown disfigurement
Notes: mostly in yard trees; pick up and destroy all fallen branches

Other periodic hickory defoliator: hickory tussock moth

Locust

Pest or Condition: locust leafminer
Evidence: adult skeletonizing of lower leaf surface, followed by larval mining
Effect: widespread annual browning of locust foliage; growth, vigor reduction
Notes: adult beetle overwinters, feeds and lays eggs in spring; larvae feed in
common mine initially, then mine separately; two generations

Pest or Condition: locust borer
Evidence: entrance holes, frass, galleries, poor form
Effect: poor growth; riddled stem susceptible to wind breakage
Notes: tends to be worse on poor sites; can be reduced through sanitation

Pest or Condition: rimosus heart rot
Evidence: hard, woody, brown, perennial conk; decayed heartwood
Effect: renders wood unusable
Notes: very common; not lethal; remove infected trees

Maples

Pest or Condition: Verticillium wilt
Evidence: leaf stunting, chlorosis, scorch, death; green to brown sapwood stain
Effect: branch mortality, sparse foliage, slow growth or tree mortality
Notes: affects many woody plants; susceptibility varies among maple species;
usually begins in roots; nitrogen fertilization can sometimes arrest disease

Pest or Condition: yellow-bellied sapsucker
Evidence: horizontal row(s) of more or less uniform holes in bark
Effect: bark disfigurement, sap flow; fungus infection, staining of wood
Notes: bird frequently returns to same trees; feeds on sap, occasionally on insects, buds,
cambium; hundreds of tree species affected; favorites include pines, hemlock, birches, beeches, aspens, maples

Occasional maple defoliator in eastern Virginia: whitemarked tussock moth

Oaks

Pest or condition: defoliators (many species)
Evidence: partial to complete leaf loss any time after spring bud swell
Effect: growth, vigor reduction in rough proportion to leaf loss and time of year
Notes: early season, heavy defoliation results in refoliation, which reduces food reserves and predisposes tree to secondary pests; can lead to mortality; proper fertilization will help weakened yard trees recover; less impact from late season defoliators. Among the major oak defoliators are fall cankerworm, oak skeletonizer, oak leaftier, gypsy moth, forest tent caterpillar, buck moth, variable oakleaf caterpillar, scarlet oak sawfly, linden looper

Pest or condition: decline
Evidence: progressive crown dieback from top down and outside in; premature leaf coloration; attacks of secondary organisms, especially shoostring root rot and two-lined chestnut borer

Effect: decline over several years, often leading to mortality
Notes: episodes have been associated with advanced age, drought, shallow soils,
early season defoliating insects and disturbance from construction

Pest or condition: galls
Evidence: abnormal growths on leaves, twigs, roots
Effect: usually none; can lead to early leaf fall, stem breakage
Notes: hundreds of kinds on oaks alone; most caused by insects

Pest or condition: leaf blister
Evidence: convex/concave distortions of leaf blade; a few spots to whole leaf
Effect: can lead to partial defoliation
Notes: shows up early in season; sometimes widespread

Pest or condition: shoestring root rot
Evidence: black, string-like rhizomorphs between dead bark and wood
Effect: usually accelerates decline and death of trees weakened by other agents
Notes: many species of varying virulence; ubiquitous; also causes decay

Pest or condition: borers
Evidence: holes, frass, sap flow, galleries, bark irregularities
Effect: wood product defect and degrade; can lead to stem breakage
Notes: development often takes more than one year; heavily infested brood trees timber
stands should be felled

Pest or condition: scale insects
Evidence: presence of sooty mold; scale covers; bark abnormalities; tree decline
Effect: generally innocuous in forest stands; can be lethal to yard trees
Notes: natural enemies usually effective; heavy infestations on yard trees should be suppressed;
horticultural oils effective

Pest or condition: anthracnose
Evidence: small to large, brown patches on succulent leaf tissue; sometimes
causes distortion; patches often bounded by veins
Effect: can cause partial defoliation, twig dieback, reduced growth
Notes: weather related; no practical treatment; susceptibility varies among species

Pest or Condition: oak wilt
Evidence: leaf wilting, color change to yellow, bronze, tan; leaf drop; sap stain
Effect: tree mortality, particularly among the red oak group
Notes: found west of Blue Ridge; can kill tree quickly; moves slowly tree-to-tree

Pest or condition: periodical cicada
Evidence: mass emergence, singing; oviposition wounds leading to twig mortality
Effect: damage to fruit bearing branches; partial defoliation; some growth loss
Notes: up to several broods per county, each on a different 17- or 13-yr. cycle

Pest or condition: twolined chestnut borer
Evidence: dieback; mortality; D-shaped exit holes; winding galleries
Effect: infestations often begin in top and move downward; intersecting galleries in outer
sapwood and inner bark tend eventually to girdle and kill tree
Notes: frequently found in trees weakened by defoliation and infected by shoestring root rot

Pest or Condition: acorn feeders
Evidence: empty or damaged acorns
Effect: poor to no seedling development; loss of mast for wildlife
Notes: many species of insects, mostly weevils, destroy a high percentage of acorn crops annually;
can have a major impact on regeneration, wildlife

Sycamore

Pest or Condition: anthracnose
Evidence: emerging leaves turn dark brown; larger leaves with brown patches
Effect: leaf fall; thin crowns, twig dieback
Notes: very common; early symptoms easily confused with freeze injury

Pest or Condition: lace bugs
Evidence: insects clustered under leaves; foliage stippled to almost entirely brown
Effect: discoloration, early leaf fall
Notes: adult lace bugs flat, whitish with lacelike wings; many species; most have two
generations a year; stay on undersurface of leaves

Other common sycamore defoliator: sycamore tussock moth

Yellow Poplar

Pest or condition: leaf weevil
Evidence: multiple, oval or crescent-shaped holes, mining in leaves; defoliation
Effect: repeated partial defoliations weaken trees
Notes: a periodical problem in southwestern counties; often over large areas

Pest or condition: Columbian timber beetle
Evidence: entrance holes about 2 mm in diameter; exude frass and sap; branched tunnels into heartwood

Effect: galleries and associated stain devalue wood; infestation can build over time
Notes: ambrosia beetle -- food is fungus grown in galleries; does not eat wood

Pest or condition: aphids
Evidence: profuse honeydew, often with sooty mold beneath infested trees
Effect: nuisance from honeydew, sooty mold on lawn furniture, sidewalks, cars, etc., and from ants,
wasps, bees attracted to honeydew
Notes: severe infestations can cause distortion of succulent tissues; some aphids cause galls;
virtually all tree species play host to aphids