Tree Disorders Identification List

Air Pollution The effects of pollutants on trees can cause the tree to weaken and die. Trees have less resistance to diseases and insects when pollutants enter their pores, according to the U.S. Department of Agriculture’s Forest Service Department Ozone near the ground interferes with photosynthesis by blocking sunlight. Ozone pollution in Los Angeles has killed some ponderosa and other pine species. Ozone has also affected white pine tree survival in Canada and the Eastern United States. Causes loss of leaves.

Air Pollution

Aphids Aphids are tiny little sucking insects, 1/8 inch or smaller. They suck the juice out of plants and they can also transmit plant virus diseases. Yellowing of leaves and deformed new growth are symptoms. Look on stems and on the undersides of leaves. Aphids can be white, green, yellow, red, even black, depending on the species. Green or white aphids are the most common. Can leave white residue. Aphid infestations are easy to identify, because they leave the leaves looking puckered, yellowed and twisted. In severe cases, they will cause the leaves to drop and the branches to die.

Aphids

Beetles Beetle adults are small, cylindrical, hard-bodied insects about the size of a grain of rice. Most species are dark red, brown, or black. A buckshot pattern of holes is apparent on the bark surface of infested branches or trunks where the new adults have emerged. Larvae of most species are off-white and grub like, and may have a dark brown head. Tunnels resemble centipede on wood surface and the inner bark; adults feed on and kill twigs, shot holes in bark indicate damage attack midtrunk of large trees, bubbling holes with boring dust indicate damage.

Beetles

Heart rot disease in living trees is caused by fungi which have entered the tree through open wounds and exposed bare wood. Usually a conk or mushroom "fruiting" body is the first sign of infection. All deciduous trees can get heart rot. Butt rot disease is the most common disease affecting hardwoods. Many fungi are capable of causing root rots and some cause considerable decay of the butts of trees as well. Butt and Heart Rot

Butt or Heart Rot

The term "canker" disease is used to describe a killed area in the bark, the branch or the trunk of an infected tree. Dozens of species of fungi cause canker diseases. Canker

Canker

Herbicides most often damage trees when they come into contact with and are absorbed by the roots. Trees affected by herbicides have yellow, spotted or deformed leaves and a spiraling pattern of dying tissue up the trunk. Browning or yellowing of the leaf margins and brownish or discolored irregular areas on leaves are common symptoms of chemical burns. Severe injury may be evidenced by distortion of new leaves, or defoliation. Chemical Damage

Chemical Damage

Cicadas can damage small twigs and branches because the female will deposit her eggs inside small branches the size of a pencil. The twigs die when the female bores under the twig bark to place her eggs. The dead twig’s color contrasts with the green leaves. This is called “flagging”. Young trees are the most severely damaged by flagging because they have more branches of the preferred size for egg laying by the cicada. Although Oaks are commonly attacked, the most serious damage occurs on newly planted ornamental, deciduous trees. Pines and evergreens are not usually attacked. Cicada

Cicada

Damping-off is a disease of germinating, and newly emerged, conifer and hardwood seedlings that results in decay of succulent tissue, wilting, and seedling death. Pre-emergence damping-off occurs when fungi infect developing radicals and kill seedlings while shoot tissues are still below ground. Post-emergence damping-off occurs when fungi infect the succulent tissue of germinants with aboveground shoots, causing decay, wilting, and death Damping Off

Damping Off

Douglas Fir Tussock Moth Caterpillars of the Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), chew the needles of spruces, Douglas fir and true firs. During outbreaks they may cause extensive defoliation, with injury typically first concentrated at the top of the tree. Older caterpillars may rapidly defoliate a tree and tops may be killed Douglas Fir Tussock Moth

Douglas Fir Tussock Moth

The adult beetles nibble on ash foliage but cause little damage The adult beetles nibble on ash foliage but cause little damage. The larvae (the immature stage) feed on the inner bark of ash trees, disrupting the tree's ability to transport water and nutrients Initial damage appears as thinning in the upper canopy of the tree as larvae feed under the bark they damage the conductive tissue. However, other conditions can cause canopy die-back in ash trees, and this symptom does not specifically indicate EAB. Emerald Ash Borer

Emerald Ash Borer

Fire Damage

The larvae move to the leaves of trees and begin to eat, mostly at night It has a preference for the leaves of deciduous hardwood trees such as maple, elm, and particularly oak. Gypsy moths appear to dislike ashes, sycamores, butternuts, black walnuts, dogwoods and balsams. Depending on the degree of infestation, tree damage ranges from light to almost complete defoliation. Most deciduous trees can survive a moderate degree of defoliation. Many can even survive one complete defoliation by the gypsy moth caterpillar. However, continuing attacks can fatally weaken a tree or leave it vulnerable to other insects or disease. Gypsy Moth

Gypsy Moth

Hemlock Woolly Adelgid The hemlock woolly adelgid is tiny, less than 1/16-inch (1.5-mm) long, and varies from dark reddish-brown to purplish-black in color. As it matures, it produces a covering of wool-like wax fi laments to protect itself and its eggs from natural enemies and prevent them from drying out. This “wool” (ovisac) is most conspicuous when the adelgid is mature and laying eggs. Ovisacs can be readily observed from late fall to early summer on the underside of the outermost branch tips of hemlock trees Hemlock Woolly Adelgid

Hemlock Woolly Adelgid

Landscape Equipment Damage Compacted soil from walking over and wheel barrows prevents sufficient moisture and oxygen from reaching the tree roots. Landscaping equipment such as weed-eaters and lawn mowers can cut the tree, which harms it. Landscape Equipment Damage

Landscape Equipment Damage

Tall trees, lone-standing trees, and trees growing in extremely moist soil, such as a lake or river bank, are extremely susceptible to lightning strikes. The moisture in a tree acts as a conductor for the high power electrical discharge of a lightning bolt. In some cases only the bark is affected. In other cases the heartwood may be split. Lightning strikes can also cause a tree to burst into flames. Lighting Damage

Lighting Damage

Unprofessional pruning or slashing a tree trunk with a backhoe can do irreparable harm Rototilling can destroy the majority of the tree’s roots, starving and suffocating the tree to death Mechanical Damage

Mechanical Damage

Broadleaf mistletoe absorbs both water and mineral nutrients from its host trees. Healthy trees can tolerate a few mistletoe branch infections, but individual branches may be weakened or sometimes killed. Heavily infested trees may be reduced in vigor, stunted, or even killed, especially if they are stressed by other problems such as drought or disease. Mistletoe

Mistletoe

The formation of these galls damages the water- and nutrient-conducting abilities of the roots. Root knot nematodes usually cause distinctive swellings, called galls, on the roots of affected plants. Worm-like microscopic organisms harm the roots leaving defoliation on pines known as Pine Wilt Disease. Nematode

Nematode

Spindle-shaped swellings or galls develop on branches or main stems Spindle-shaped swellings or galls develop on branches or main stems. On older trees, infections are somewhat depressed on one side. The fungus produces orange spores on pine galls in the spring. On oaks, orange spores appear on lower surface of leaves. Infected areas may grow for many years until they eventually girdle and kill the branch or stem, or they may become inactive. Rust

Rust

Pine sawfly eggs are laid in clusters and newly hatched larvae frequently feed close together. Often there may be 50-100 larvae feeding in a group. Young larvae eat the outer tissue of the needles while older larvae eat the entire needle and may cause severe defoliation. The insects are most active during late summer and fall. No tree mortality resulting directly from needle loss has been reported but severe defoliation causes loss of tree vigor and increases susceptibility to attack by bark beetles. Larval feeding may can cause unsightly damage to ornamental or landscape plantings as well as trees in nurseries. Sawfly

Sawfly

Some scale species, when abundant, weaken a plant and cause it to grow slowly. Infested plants appear water stressed, leaves turn yellow and may drop prematurely, and plant parts that remain heavily infested may die. The dead brownish leaves may remain on scale-killed branches, giving plants a scorched appearance. If the scale produces honeydew, this sticky excrement, sooty mold, and the ants attracted to honeydew can annoy people even when scales are not harming the plant. Scale

Scale

The newly hatched budworm larva is very small and difficult to find because it bores into and feeds on needles or expanding buds. These larvae can cause severe damage to the expanding buds. As the larva grows, needles are severed at the base and left hanging in a thin silken web. The severed needles turn brown, giving the defoliated tree a scorched appearance Spruce Budworm

Spruce Budworm

Sunscald often is called southwest injury because it most often occurs on the southwest side of young tree trunks. High intensity sunlight, which occurs at a lower angle in the sky during the winter, heats up the south and southwest side of deciduous tree trunks. This causes cells to come out of dormancy and become active. After sunset or as weather changes, temperatures may drop below freezing. This temperature drop kills active cells and conductive tissue. This injury may appear as sunken, discolored bark. Also this bark may crack or fall off in patches, revealing dead tissue underneath. Young, thin-barked deciduous trees, such as honey locusts, fruit trees, ashes, oaks, maples, lindens and willows are at highest risk Sunscald

Sunscald

Defoliation of trees, building of unsightly silken nests in trees, and wandering caterpillars crawling over plants, walkways, and roads cause this insect to be a pest in the late spring and early summer. Eastern tent caterpillar nests are commonly found on wild cherry, apple, and crabapple, but may be found on hawthorn, maple, cherry, peach, pear and plum as well. While tent caterpillars can nearly defoliate a tree when numerous, the tree will usually recover and put out a new crop of leaves. In the landscape, however, nests can become an eyesore, particularly when exposed by excessive defoliation. The silken nests are built in the crotches of limbs and can become quite large Tent Caterpillar

Tent Caterpillar

Slime flux or Wet Wood is a foul-smelling and unsightly seepage of sap from the trunk of shade trees. It occurs in apple, birch, elm, hemlock, maple, mulberry, oak, poplar and willow. Slime flux is a bacterial disease. The infected wood is frequently discolored or appears water soaked. Gas (carbon dioxide) is produced by fermentation by bacteria. The gas produces pressure in the wood. This pressure forces sap from the trunk through cracks in branch crotch unions, pruning wounds, lawn mower wounds, other injuries and occasionally unwounded bark. This oozing of sap is termed fluxing. The flux is colorless to tan at first but darkens upon exposure to the air. As fluxing continues, large areas of the bark become soaked. Wetwood or slime flux

Wetwood or slime flux

Wildlife/Livestock Damage Woodpeckers- at times cause damage to buildings with wood siding, especially cedar and redwood Deer- Damage to trees caused by antler rubbing can be severe. Browsing of hardwood saplings and young fir trees in regenerating forests can reduce growth rates and misshape trees Porcupines- in winter feed on inner bark of trees Livestock- Compaction of the soil results in a tree's inability to absorb needed nutrients and water. Additionally, the roots are often damaged, and these injuries serve as a source of entry for decay organisms. They often scrape and peel the bark off at the base of the tree. These injuries are points of entry for decay organisms that further reduce the quality of the tree. Wildlife/Livestock Damage

Wildlife/Livestock Damage -sheep Deer- Wildlife/Livestock Damage Porcupine-

Wood-boring insects are among the most destructive pests of ornamental trees and shrubs. Borers are the larvae, or immature stage, of certain moths and beetles. They tunnel and feed under the bark in living wood, destroying water- and sap-conducting tissues. This causes girdling, branch dieback, structural weakness, and decline and eventual death of susceptible plants. Infestation sites also provide entry points for plant pathogens. Wood Borer

Figure 1b. Coarse, sawdust-like frass exuding from cracks in the bark from clearwing borer Wood Borer