Bronze birch borer or Agrilus anxius

• Eventually twigs and then branches dieback starting at the top of the canopy and progressively working its way down
• Foliage at top of the canopy first becomes sparse
• Raised lumps or ridges can be seen on the trunk and branches
• D-shaped exit holes can eventually be observed on the trunk and branches
• S-shaped galleries can be seen under the bark
• Preferred hosts are European white birch and white-barked Himalayan birch; paper birch, gray birch are also attacked; river birch is rarely infested

Identifying infested trees is challenging
Look for these symptoms:

• Wilting or yellowing of leaves and dieback starting at the top of the tree. There can be other problems that can cause similar symptoms in the canopy so dieback is not automatically due to borers.
• As the tree continues to decline, dieback extends down into major branches and eventually into the main stem.
• Sawdust packed S-shaped galleries under the bark. Bronze birch borer galleries create raised ridges in the thin bark due to calluses forming over the galleries. Twolined chestnut borer galleries can only be seen when the bark is removed.
• 1/8-inch D-shaped exit holes on trunks and branches. They can be hard to see.

Keep trees healthy, minimize stress

Trees that are stressed, from drought, defoliation or other causes, are more susceptible to damage.

To minimize stress:

• Add organic mulch to oaks and birch to improve their health. Mulch keeps soil temperatures cooler and slows the rate of moisture evaporation. It increases the water holding capacity of the soil and creates a better rooting system. Mulch is helpful for birch which has a shallower root system.
• Always keep trees well-watered.
• Avoid fertilizing stressed trees. Fertilizers increase water demand for the trees and can be injurious to them.
• If changes are being made to the landscape, make sure to protect the roots of trees. Root damage caused by soil compaction or root severing due to heavy equipment will stress trees. Remember that the roots can extend well beyond the canopy of the tree.

Using pesticides

Treating trees with pesticides to kill borers is only effective if the tree is in the initial stages of decline and dieback.

Pesticides are not effective when more than 40 to 50 percent of the canopy has been killed by borers.

Systemic pesticides

• Imidacloprid is applied as a liquid drench to the soil around the trunk of the tree (professional applicators can also apply it as a soil injection or a trunk injection).
• Dinotefuron is applied as granules to the soil directly around the tree (professional applicators can also apply it as a bark spray, soil drench or soil injection).

CAUTION: Apply these products to birch and oak trees only after flowering in the spring to reduce pesticide exposure to bees. Do not apply systemic pesticides to the soil when bee attractive flowers are planted next to trees.

Canopy sprays

Non-systemic control of borers is difficult because precise timing and coverage is necessary. Pesticide is effective if applied to the infested tree when the adult beetles are first active in early June.

Spray pesticide on the trunk and branches where the eggs are being laid. When the larvae hatch from the eggs, they will come in contact with the pesticide as they burrow through the bark.

Products containing permethrin, lambda cyhalothrin, and other pyrethroids are effective.

• Two applications are necessary.
• The first application should be applied as black locust trees bloom and the second two to three weeks later.
• Homeowners can spray small trees themselves.
• Contact professional tree care companies for treatment of larger trees.

Professional services

Contact Ostvig Tree Care when you are dealing with larger trees. Ostvig Tree Care have experience in managing borers and in handling and applying pesticides. We have access to products and procedures that are unavailable to homeowners.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

Information source: University of Minnesota Extension

Coral spot canker or Nectria cinnabarina

• Common on trees stressed by drought, recent transplant or
  other factors
• Dead branches and twigs are often first observed in early spring
• Sunken dark brown area on branch that is often cracked or has a ridge at the edge
• Raised cushion-like bumps on affected branches, may be cream
  to orange or red, turn black with age

Canker diseases are common, widespread, and destructive to a wide range of trees and shrubs. A ‘canker’ is really a symptom of an injury often associated with an open wound that has become infected by a fungal or bacterial pathogen. Canker diseases frequently kill branches or structurally weaken a plant until the infected area breaks free, often in a wind or ice storm. Some of the more common cankers are Cytospora canker found on spruce, pine, poplars and willows, Phomopsis canker found on juniper, Russian olive, Douglas-fir, and arborvitae, and Nectria canker found on honey locust, oak, and maple.

Symptoms

Cankers are usually oval to elongate but can vary considerably in size and shape. Typically, they appear as localized, sunken, slightly discolored, brown-to-reddish lesions on the bark of trunks and branches, or as injured areas on smaller twigs.
The bark often splits between the diseased and the healthy tissue, and sometimes it may ooze sap or moisture. The inner bark turns black and sometimes gives off a foul odor. The newest leaves on affected branches are usually the first to show decline symptoms. Leaves may appear smaller than normal, pale green to yellow or brown, often curled and sparse. As the fungal pathogen invades bark and sapwood, the water-conducting tissues (vascular system) become blocked or dies, causing wilting and dieback to occur. Cankers are formed by the interaction between the host and pathogen. The pathogen grows within the wood and the host tree tries to contain the growth. Cankers can take months (or years) to enlarge enough to girdle twigs, branches, or trunks.

Disease Cycle

Canker and stem dieback diseases are most common on trees and shrubs under stress. Damage results when opportunistic, living (biotic), infectious pathogens (fungi or bacteria) enter a wound during a time of plant stress, such as transplant shock, drought, or winter injury. Other stress agents that provide opportunities for canker diseases include prolonged exposure to extremely high or low temperatures, flooding, summer or winter sunscald, hail, high winds, nutritional imbalances, soil compaction, mechanical injuries (lawnmower, vehicles), animal damage, pruning wounds, root rot, insect borers, and improper planting. Most cankers are caused by fungi, which invade bark tissue on current season wood. However, some colonize both bark and inner tissue causing canker rots that persist for years. All fungal cankers contain fruiting bodies that appear as pinhead-sized, black or colored (red-orange on Nectria canker) raised bumps embedded in the bark. When present these are an important diagnostic characteristic. Unfortunately, fruiting structures are not always present and many are not easily distinguished. The spores produced by these fruiting bodies serve as inoculum for new infections, mostly in wet or damp weather.

Management

Cankers are difficult to control. No chemicals are universally registered for the treatment of cankers. The best controls are preventative ones to keep plants healthy or to prune out the diseased plant parts when practical.

Grow only trees and shrubs that are adapted to the area and site, and select resistant varieties.

Keep plants healthy and vigorous through proper planting, mulching, watering, soil management, pruning, and winter protection practices.

Avoid all unnecessary bark wounds, because many pathogen’s main entry is through injuries.

If a canker infection occurs on twigs or branches, carefully remove the affected parts several inches behind the infection. Pruning cuts should be made at the branch collar and avoid leaving stubs.

Do not prune when the bark is wet, to reduce the spread of the fungus. Pruning tools should be sterilized between cuts using rubbing alcohol or 10% household bleach.

Once a trunk canker develops, the tree may begin to seal off the area by forming a callus around the canker. Avoid cutting into such cankers because it may renew fungal activity and increase damage. Any type of trunk canker removal is best left to a professional certified arborist.

Information source: University of Minnesota Extension

Drought

• Foliage wilts and sometimes turn brown around the edges
  but more commonly turns a dull, gray-green color
• Dried brown to gray-green leaves hang on the tree or more commonly, foliage drops prematurely and litters the ground
  under the tree
• Severe drought stress may cause dieback of individual branches starting at branch tips

Information source: University of Minnesota Extension

Ganoderma root and butt rot (artist’s conk) or Ganoderma applanatum

• Leaves are smaller in size and turn yellow earlier than normal
• Canopy appears thin with few leaves and multiple dead branches
• Fungal conks, a semicircle shelf fungi, can be found from the base of the tree up to 3 feet high on the trunk
• Conks are reddish-brown and shiny on top, white and porous underneath; a rim of white may be visible on the edge of
  growing conks
• Infected wood at the base of the tree is white, soft, stringy
  or spongy
• Infected trees frequently break or fall over in storms

Varnish fungus rot, caused by the fungus Ganoderma lucidum and (unvarnished) fungus rot, caused by G. applanatum infect the roots and lower trunk (butt) of many deciduous trees and some conifers. They attack the lower heartwood, and at advanced stages damage the structural integrity of the host tree, often resulting in windthrow (the potential to be uprooted or broken by wind). Maples, oaks, and honeylocusts are particularly susceptible, although ashes, elms and many other deciduous trees and some conifers can be attacked.

Symptoms and Diagnosis

Trees affected by fungus rot may exhibit yellowing, wilting, or undersized leaves and dead branches. Tree vigor may decline as the decay of the sapwood advances. The first visible sign of infection is often the formation of fruiting bodies (single or in clusters) on the lower trunk and exposed root areas. The fruiting bodies are conks:  shelf-like in appearance and up to 14 inches wide. The upper surface of varnished fungus rot is typically red-brown with a white edge, shiny, and with a lacquered appearance. Conks of the unvarnished fungus rot are brown with a white edge weathering to grey. Both have a white, porous surface (when fresh) on the underside. Young trees, as well as older, larger ones, can be killed by this disease. Unfortunately, by the time the conks are noticed, it is too late to reverse the infection. The rate of decay can lead to death in as little as 3 to 5 years from the time of infection and appears to be determined by tree vigor, which is often influenced by environmental stresses.

Life Cycle

New spores released from the conks are dispersed throughout the summer during humid periods and infect open wounds on root flares and lower trunk areas of susceptible trees. The spores germinate, and the infection advances to attack the sapwood of major roots and the lower tree trunk. The amount of decayed wood increases year after year, resulting in dangerously soft, spongy wood in the part of the tree that serves as its anchor. The conks are annual; new conks may be produced each summer and fall, after which they die and deteriorate.

Integrated Pest Management Strategies

1. Proper planning.  Appropriate species and cultivar selection to match the right tree for the right site will make it easier to keep trees healthy for their entire life.

2. Proper tree maintenance. Subsequent good cultural practices (planting, fertilizing, watering, pruning, etc.) will help to maintain the health and vigor of any tree.

3. Avoid damage to tree trunks and roots. Even small wounds from mowers and trimmers can allow infection by decay fungi. Avoid damaging all deciduous trees, both young and old.

4. As soon as possible, remove trees that exhibit conks on the lower trunk and exposed root areas. Large trees with severe internal rot may fall with little warning, injuring people and causing extensive property damage. Consult a certified arborist for the removal of large trees.

Information source: Missouri Botanical Garden

Heart rot or Polyporus squamosus, Laetiporus sulphureus, Fomes
fomentarius, Phellinus igniarius, Piptoporus betulinus

• Canopy may show no symptoms or may have small yellowing leaves or dead branches depending on the extent of the decay
• In cross-section of the trunk, the wood at the center is discolored, soft, crumbling, stringy or spongy
• Fungal fruiting bodies arise along the stem; often near a pruning wound, crack or other wounds
• Many colors, shapes, and sizes of fruiting bodies may be seen

Heart disease in trees is caused by fungi invasions. Although there are many species of fungi that cause decay in living trees, most important are those fungi that cause heart decay often called heart rot. These pathogens usually enter the tree as a result of injury Such points of entry may come from broken branches caused by wind, fire, lightning, and even from improper pruning by us humans. Once inside the tree, fungi cause decay. Interestingly, heart rot fungi do not invade the living wood of healthy trees.

Detecting heart rot can be difficult. Since this type of decay takes place internally, it can remain out of sight for many years. Usually, in the latter
stages of heart rot, mushrooms grow on the trunk or branch. This is one of the first visible signs that a fungal pathogen resides within the tree. Unfortunately, as decay progresses, the heartwood is destroyed; and the integrity of the tree’s strength becomes a serious issue.

These external mushrooms are the fruiting bodies of the fungi. They are generally called conks or bracket fungi. These visible conks produces spores. Spores become wind-borne, microscopic, seed-like structures. The wind carries spores to other susceptible trees thus perpetuating the life cycle of conks. These fungi appear bracket-like, attached to the tree and varying greatly in size, color and texture. Note: The visible presence of conks
calls for investigation.

Eliminating or minimizing heart rot is accomplished by keeping one’s tree healthy. When pruning branches, make cuts just outside the branch collar so proper mending can take place. Shape trees at an early age, so major branch removal creates small wounds.
Remove broken branch stubs immediately following storm damage. Have suspected heart rot trees checked by an arborist to determine if sufficient live wood is present for structural safety. Check trees every few years to be certain new growth is maintaining sound structure.

I am certainly not a doomsday advocate, but I do know that large tree trunks and main branches revealing numerous conks are certain indications that little sound wood remains to support the tree.

After all, one doesn’t want heart disease, more commonly called heart rot, in trees to cause the homeowner heartache when his or her tree comes tumbling down damaging, or possibly destroying, his or her home.

Information source: University of Nebraska

Leaf and shoot blight or Diaporthe alleghaniensis

• Leaves wilt, die and remain attached to the branch when the canker completely girdles the branch
• Infections on young shoots cause branch tips to curl over in the form of a Shepard’s crook
• Black sunken cankers occur on bark of infected branches
• Occurs only on yellow birch

Blight is progressive dieback of young, green shoots. Leaf spot pathogens that cause dieback of young shoots typically do not progress to infect the older woody branches.

Examples of leaf spot diseases that progress to leaf and shoot blight include Aschochyta blight on lilac and Venturia shoot blight on Populus species such as poplar, aspen and cottonwood trees.

• Trees and shrubs should be carefully scouted for discolored areas of bark.
• Any infected branches or shoots should be pruned out several inches below visible signs of the infection.
• Infected branches should be burned or buried.

Information source: University of Minnesota Extension

Perennial nectria canker or Neonectria galligena

• Dead branches and twigs killed by girdling cankers
• Sunken target shaped cankers on main trunk or branches
• Cankers do not have bark and raised ridges of wood occur in target-like rings within the canker
• Red to reddish orange raised cushion like bumps can occasionally be seen on the edge of the canker

The fungus Neonectria (Nectria) galligena causes perennial Nectria canker on branches and stems of angiosperm trees and shrubs.

Initial infection occurs at leaf scars, branch stubs, cracks in branch axils, sunscald lesions, and other wounds to the bark that expose the cambium. Most spores are wind and rain splashed during the spring and the fall from nearby established cankers. The tree typically responds to a perennial Nectria canker by compartmentalizing the infection with, among other responses, a cork barrier. Once established in the cambium the Nectria fungus grows through the callus during the dormant season, killing the bark, cambium, and the outermost sapwood as it progresses. Clumps or individual red to orange fruiting structures can appear from autumn to spring on the surface of young cankers. The next growing season the tree responds to the breach in its defenses around the canker by forming another compartmentalization barrier. During the ensuing years as the tree and the Nectria fungus alternate with their respective growth responses, the series of callus ridges develop a target pattern.

Once perennial Nectria canker establishes itself in a tree, interventions focus on sustaining the vitality of the tree. Remove infected branches when the weather is too cold or dry for the fungus to infect the pruning wounds, and dispose of the debris away from the trees. Irrigate when conditions are dry, fertilize if soils are deficient in minerals, prune to preserve sound branch structure, avoid wounding the bark, and maintain 2-3 inches of composted mulch over as much of the root zone as possible.

Information source: University of Massachusetts Amherst