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Whats wrong with my tree?

A lot of people don’t realize it, but trees get sick—kind of like we do. And like us, trees are more susceptible to disease when they’re stressed and unhealthy.

If your tree isn’t looking so hot, one or more of the following things might be going on:

 

1. Fungal Infections
2. Bacterial Infections
3. Insects and Other Pests
4. Structural, Environmental, and Nutritional Issues

Fungal Infections

Fungal infections often occur in areas where humidity and soil moisture are high. Fungal disease such as phytophthora often occurs as a result of overwatering a landscape. The abundant moisture around the tree’s roots gives the pathogen the opportunity to spread and thrive in a tree. Some fungal infections such as oak wilt can be so devastating that certain species of trees with this disease will most certainly die within a few years.

Bacterial Infections

Bacterial infections can also devastate a tree. They’re often spread by insects or may already live in the soil. These infections can cause a variety of problems including blackened and dying leaves, as well as oozing cankers that have the potential to cut off water and nutrients to the tree.

Insects & Pests

There are a bunch of tree damaging insects that can plague your tree. Insects such as tree mites, wood boring insects, and scale are a few that can cause serious damage. Tree mites are pesky, little, spider-like creatures that feed on the undersides of leaves. Wood boring insects are often host-specific; meaning a particular species of bug tends to prefer destroying a particular species of tree. For example, the Emerald Ash Borer destroys only ash trees. With most wood boring insects, it is the larvae, or the young caterpillar-like stage, that feeds on and destroys a tree. While scale spends most of their lives immobile, they can cause a surprising amount of damage.

Structural, Environmental & Nutritional Issues

Do you know what a root flare is? The root flare of your tree is also known as the root collar, root crown, or trunk flare. This is area at the base of the tree where the roots and stem come together. It should be exposed to the air and not buried under mulch or soil. Many homeowners make the mistake of piling mulch or soil too high around the base of the tree so that root flare can’t breath. This is the cause of many tree diseases and can be easily avoided. Check your trees to see if the root flare is exposed. If it isn’t simply remove the soil or much by pushing it back away from the trunk.

 

The health of the tree ultimately lies in the soil. To help prevent disease get a soil test to check for any important tree nutrients that are lacking and to check the soil pH level. Most landscape trees enjoy a pH around 6.5, anything much lower or higher can jeopardize the health of your tree. Have no fear, soil quality can be managed and brought to the appropriate level of nutrition and pH that your tree will love!

 

Finally, it’s important to note that improper pruning is often the source of tree infections. The wounds left from improper pruning are open doors to these pathogens. Learn proper pruning techniques or consult with a certified arborist about pruning your tree for optimal health.

Common Tree Diseases & Conditions

Oak Wilt

Oak Wilt

Fungus

Trees Affected

More than 20 species of oak trees are susceptible to this deadly disease. The most vulnerable are in the red oak group. Red oaks include the scarlet oak, Shumard oak, willow oak, northern red oak, and black oak, among others. Oaks in the white oak group are also affected, most notably the southern live oak, and Texas live oak because of their extensive system of grafted roots between trees. Other white oaks susceptible to oak wilt include white oak, bur oak, overcup oak, and post oak.

Symptoms

Leaves of live oaks become chlorotic (yellow) or bronze, often with brown tips and yellow to brown color along the veins. Diseased trees may lose their leaves and die quickly, but some survive several years, showing progressive dieback and producing adventitious sprouts with small leaves on the trunks and large limbs. Some trees will form mats of fungus on the surface of the wood and inner surface of the bark on the trunk. The mats are oval shaped and can range from 2.5 to 20 x 1 to 10 cm in size. They start out gray and turn black with age. These fungal mats may cause the bark to crack open, allowing access to insects. Fungal mats are most often found on infected trees in the red oak group.

How it Spreads

C. fagacearum overwinters in diseased trees. Sap-feeding beetles visit the fungal mats and become covered with the disease. Later, these insects visit fresh wounds of healthy trees and spread the disease. Pruning wounds on shade trees are common sites of infection where Oak wilt occurs near-by.

 

Oak wilt can also spread through the naturally grafted roots of trees growing near each other. Live oak trees are especially susceptible to infections because of their system of shared, or grafted, roots.

 

Another cause of spread is tree trimmers using pruning the limbs of infected trees and then infect other trees by using those same tools without proper cleaning.

How To Control it

Pruning during the dormant season or during summer can minimize the danger of oak wilt infections through pruning wounds. Girdling or cutting-down newly diseased trees can also reduce oak wilt hazard. This prevents or slows down fungal mat production. You can suppress oak wilt symptoms in live oaks with regular injections of fungicide.

 

You can also inoculate healthy oaks to prevent them from catching it.

Anthracnose

Anthracnose

Fungus

Trees Affected

There are several different species of fungus that cause anthracnose disease. Anthracnose affects many trees including elm, ash, oak, sycamore, walnut, hickory and pecan, dogwood, birch, redbud, maple, hornbeam, camellia, citrus, pine, and fig.

Symptoms

Because there are several different strains of anthracnose that are specific to certain kinds of trees, the symptoms can vary greatly. For example, elm trees will experience black spots and blackening leaves as the disease spread and kills living cells. On oak trees anthracnose causes a brownish-bronze die-back of the leaves as well as small pimply cankers along the twigs and small branches. On sycamore trees it causes shoot tips and leaves as well as large cankers along the trunk and branches. On nut trees such as walnut, pecan, and hickory anthracnose causes yellow patches to form on the leaves along with brownish-black dead tissue.

How it Spreads

The fungus lives on the tree year round, overwintering in the dormant buds. In the springtime the fungus begins to grow and infect new areas of the tree. Fallen leaves also harbor the disease and can perpetuate the problem if they are not raked away and burned. The fungi can actually shoot into the air in an attempt to spread onto healthy leaves. When the fungus lands on a new victim, it produces a germ tube that can penetrate leaf cell walls. The fungus then goes to work to kill the leaves and cause unsightly cankers.

 

The disease thrives in wet or moist environments and can increase during rainy weather, especially during the spring. When plant leaves remain wet for several hours, the disease is more likely to occur.

How To Control it

Removing diseased leaves and limbs that have fallen from the tree is an important part of limiting the spread of anthracnose. Pruning the tree to remove diseased limbs will also help. A proper pruning job will also increase light penetration and air-flow around the leaves and branches, thereby decreasing the likelihood of infection.

 

Fungicides may be applied in the winter, before bud break. This will kill the fungus before it has a chance to re-infect the tree, although never fully getting rid of the disease.

Bacterial Leaf Scorch

Bacterial Leaf Scorch

Bacteria

Trees Affected

Bacterial leaf scorch, or BLS can affect many different kinds of trees and shrubs including maples, pecans, buckeyes, American beautyberry, hackberry, dogwood, sweetgum, mulberry, oleander, sycamore, almonds, plums, oaks, elderberry, elms, and grapevines. There’s a good chance you have at least one of the trees listed.

Symptoms

The bacteria essentially clog the water and nutrient conducting system (xylem) in the tree, causing a number of symptoms. Trees will most likely show a marginal reddening or yellowing followed by brown leaves, decreased fruit or flower production, reduced vigor, later budbreak, stunting, dieback and sometimes death. The leaves will usually show signs during mid to late summer when the weather becomes warm and dry.

How it Spreads

The disease is usually introduced to the tree from an insect vector or root graft. Once introduced, the bacteria multiply in the xylem sap and are carried with it both upward and downward-eventually infecting your entire tree. In the US, leafhoppers (a common leaf chewing insect) are vectors for the disease. The adult leafhoppers can carry the bacteria around with them for several days, infecting many trees as they move around.

How To Control it

Unfortunately, there is no cure for BLS, but there are ways to increase the lifespan of your infected tree. A yearly application of the antibiotic tetracycline can alleviate symptoms and improve the health of your tree.

 

The best management tool for this disease is to keep your tree as healthy as possible. This will give it the power to slow down the spread of BLS through its system.

Fire Blight

Fire Blight

Bacteria

Trees Affected

Fire blight affects plants in the rosaceae, or rose, family including apple and pear trees, hawthorn, quince, and Pyracantha (firethorn). Ornamental and fruit producing trees can be plagued by fire blight.

Symptoms

The main signs of this disease occur on the blossoms, young fruits, and leafy shoots. It can also reveal itself in cankers and dieback. Blossom blight is usually the first new symptom each year. Flowers and flower clusters appear water-soaked and darkened, then quickly droop, shrivel, and turn brown or black. If many shoots are blackened at the same time the tree may look scorched or burned, as the name implies.

 

Cankers may occur in twigs and branches. During the growing season the margin or active cankers may appear slightly raised or blistered. Cankers can also occur on the trunks or root collars as a result of infected basal shoots or wounds by bacteria carried in water from diseased parts above. These cankers may girdle and kill entire trees.

 

During humid weather or after rain, drips of cream to honey colored or orange slimy fluid called ooze emerges from pores of the tree and tiny wounds on recently infected parts.

How it Spreads

Fire blight bacteria overwinters in diseased tissue at the edges of cankers. It also overwinters in buds and twigs infected the previous season. The bacteria is active during warm weather in the spring and summer. The bacterial ooze unfortunately attracts insects that can become covered and then spread it to a healthy tree. Water splashed onto the ooze can also move the bacteria from an infected tree to a healthy one. Birds and humans can also be accidental spreaders of the disease. However, the most common spread of the disease comes from pollinating insects.

 

Fire blight epidemics occur in warm, humid weather during bloom time (usually early spring). Large outbreaks of fire blight often occur after storms with heavy rain, hail, and strong winds. Devastating epidemics sometimes follow hail storms because the bacteria enters the wounds. Damage by insects such as cicadas that wound stems also promotes infections.

How To Control it

Many fruit growers predict outbreaks using weather data (warm humid springs) and spray preventative anti-bacterial products before infections can occur.

 

Avoid heavy fertilization that may encourage new growth because the bacteria tends to cultivate itself on new growth. Plants growing in well-drained, moderately fertile soil with a balanced supply of nutrients are least damaged by the disease.

 

There are some varieties of trees in the rose family that have some resistance to the disease. Bradford pear, for example is rarely affected and then sustains only minor damage. Resistant firethorns include ‘Pyracantha coccinea ‘Sensation’, and P. koidzumii and its cultivar ‘Santa Cruz Prostrata’.

 

Destruction of ornamental plants by fire blight can be delayed or halted by carefully pruning out all blighted twigs or branches, making cuts at least 4 to 5 inches below cankers or margins of dieback. Do this while plant surfaces are dry, preferably during the winter. Also remember to practice sanitary pruning methods.

Tree Boring Insects

Wood Boring Beetles

Insects / Pests, usually secondary invaders

Trees Affected

Many shade trees can become victims of wood boring insects. Woodborers tunnel into the inner bark layer, which transports nutrients and water to the leaves. Their tunnels eventually block the cambium and girdle the plant. Eventually everything above the damaged site dies. There are many species of tree boring insects that are host specific, while some insects are not so picky.

Symptoms

Unfortunately the problem of wood boring insects often goes unnoticed until plants or plant parts begin to die or show external signs of damage such as dying limbs or leaves. You may notice small and randomly distributed holes in the bark.

How it Spreads

Adult borers emerge from infected trees in the spring and summer. After mating, the females fly to a suitable host and lay eggs on the bark, often into crevices or around the wounds. The eggs hatch about 10 days to 2 weeks later. The young larvae quickly tunnel beneath the bark where they feed and grow. Once inside the tree, the borer larvae are no longer vulnerable to insecticide spray and are rarely detected until serious damage has been done.

How To Control it

Many of these insects are attracted to stressed-out trees. Sick trees actually release unique chemicals that wood-boring insects can smell. It’s important to keep your trees happy and healthy with proper pruning and soil health.

 

An arborist with an applicators license can apply insecticides to prevent the adult wood borers from laying eggs and entering your tree. There are a few insecticides designed to be applied as trunk-injections while some are applied as foliar sprays. The treatments should be timed to match adult insect activity. Insecticides are most effective if applied when the adults are emerging and laying eggs.

 

Unfortunately, once trees and shrubs are infested, your options for control are a bit more limited. One option is to remove and destroy heavily infested or injured plants. Also, inspect damage sites closely to determine if the larvae can be extracted from the plant with a pocketknife.

Tree Mites

Tree Mites

Insect-like Pest

Trees Affected

Tree mites feed on many shades trees such as oaks, maples, and others. They also affect shrubs such as camellias and azaleas, as well as fruit trees and vegetables.

Symptoms

You may first notice mite damage as tiny yellow or bronze spots on the leaves of your tree. You may also notice the tree not looking as healthy and vigorous as it should. If you were to turn over a leaf on a mite-infested tree, you will see the tiny critters living there, feeding on your tree. On a light to moderately infested tree, the yellow or bronze spots tend to be concentrated around the leaves’ midrib and large veins. Leaves on more heavily injured plants can become yellowed, bronze, and fall off.

How it Spreads

Somehow these guys will find an opportunity to infest a stressed plant where predatory insects populations are low. They will set up shop to spread their kind, take over, and go to town on the juicy leaves of your tree.

 

You may be surprised to learn that mite populations often get larger after insecticides have been sprayed. Because mites are more closely related to spiders than insects, insecticides rarely affect them. In fact, it is the good insects such as ladybugs, lacewings, and predatory mites that keep the pest mite populations low.

How To Control it

A healthy tree growing in an environment where beneficial insects are active will rarely have trouble with mites. Try to limit the use of insecticides in your landscape to increase populations of beneficial insects.

 

If the problem is not too large, blasting water on the plant daily until the problem is gone can eliminate them. Natural enemies of mites also help to keep the problem under control. Their natural enemies include predatory mites, ladybugs, assassin bugs, wasps and other insects.

 

Miticides are also available and effective means of controlling large populations of mites. Miticides are chemicals specially formulated to kill mites. When you apply the miticide, be sure the wind is not too strong. Be sure you reach the undersides of the leaves where the mites are active. For best results, contact a tree health specialist to apply it for you.

 

The best way to avoid a mite outbreak is to observe your tree’s overall health. Proper watering that allows the soil to dry out between watering and providing your plants with rich nutritious soil can go a long way in keeping your trees healthy.

Phytophthora

Phytophthora

Fungus

Trees Affected

Unfortunately, not many trees are spared from this ubiquitous fungal pathogen. At least one, if not several species of Phytophthora can infect many forest trees, shade, and ornamental trees. It causes a variety of symptoms in a variety to tree species, one of which is root rot. Oak and dogwood trees are particularly susceptible to Phytophthora root rot.

Symptoms

Phytophthora species can cause a variety of symptoms in trees. In many cases the leaves will appear stressed and may turn dull green, yellow, red or purple. If left untreated the tree can survive for a few years before the disease kills it.

 

You may also notice the color of the bark at the base of the tree appears darker than usual. If you cut away some of the bark, the wood should appear reddish brown if infected with a phytophthora species.

 

Phytophthora may also cause shoot blight, dieback, and wilting. The fruits of many trees will rot when infected. Phytophthora will also cause crown cankers or root rot. It can redden and kill the top branches of dogwood trees. The cankers caused by this disease may have a black ooze coming from them.

How it Spreads

Phytophthora species can survive in the soil for years, as long as the soil stays moist. Like other bacterial and fungal tree diseases, it can spread through splashing rain, irrigation water, and runoff water. Lawns with a sprinkler system that keep the ground constantly moist are particularly susceptible to this fungal pathogen.

 

Phytophthora can be spread through contaminated soil from a garden center to your home, or on borrowed gardening equipment. This is true of many soil dwelling plant diseases. Cleaning gardening equipment after a neighbor or a friend has used it will help prevent the spread of the disease from one landscape to another. Also be sure that the nursery where you purchase plants is effectively managing for Phytophthora. You would hate to introduce this into your yard by accident!

 

Rainy weather also enhances the spread of phytophthora throughout the landscape. In flooded conditions (any standing water, really) the fungus produces swimming zoospores that can move through water in search of plant roots to infect. Therefore improving soil drainage in the landscape will help reduce the spread of this tree disease.

How To Control it

Don’t worry, this disease can be managed so that your tree will continue to live a long life. There are many fungicides registered to kill Phytophthora. A tree health specialist can help you make a plan to save your tree.

 

Using foliar sprays along with an early spring and/or late fall soil drench is a good method of prevention. This will protect the plants early and include two different types of fungicide chemistry.

 

Finally, apply foliar nutrients to make up for rotting fibrous roots’ loss of uptake. This form of fertilizing is sprayed on the plant’s leaves where the nutrients are taken up. But avoid excessive nitrogen fertilization, which encourages the spread of Phytophthora.

Seiridium Canker

Seiridium Canker

Fungus

Trees Affected

The disease caused by Seiridium sp. infects species of trees in the Cypress families; Cupressaceae and Taxodiaceae. Seiridium sp. have caused severe damage in Africa, Japan, the Mediterranean region, New Zealand, and the United States. In the 1920’s an aggressive strain of the disease began destroying populations of Monterey cypress (Cupressus macrocarpa) and Italian cypress (C. sempervirens) in California. From there it was spread around the world.

 

Trees that can become infected with seiridium canker include Monterey cypress, Italian cypress, Leyland cypress. This disease can also damage the Lawson cypress, Hinoki-cypress, Sawara cypress, Portuguese cypress, eastern red cedar as well as the Oriental arborvitae.

 

Trees that are resistant, including bald cypress and western red cedar, halt infection rapidly and then form a cork barrier that isolates the disease.

Symptoms

Girdling cankers on twigs, branches, or the main stems cause fading and death to the foliage. The cankers are usually lens shaped and become sunken as diseased bark dries and surrounding tissue grows around it. Some cankers, especially on young fast growing trees, will exude a black resin. Older, slower growing trees rarely show resin coming from the cankers. Large trees infected with seiridium cankers may slowly decline over many years from the cumulative effects of multiple cankers. Death comes quicker if the tree also suffers from drought or insect pressure.

How it Spreads

Like most fungi, seiridium fungi are mobile during wet weather. Rainy springs or even an overused sprinkler system can invite the spread of this destructive disease. Wounds on the twigs, branches, or trunks of your trees are often the place where an infection can start. Pruning tools and infected seed have been known to spread the disease. Insects can also move the fungi from an infected tree to a healthy one.

How To Control it

Prune and throw away or burn infected limbs. Prune the limb 3 to 4 inches below the infected canker and don’t compost them or leave them lying around. Fungal spores are so small and light that just a light rain can send them soaring into the air to find a new host. Put them in a trash bag and then in a covered garbage can. Burning them is also a good way to kill the disease and get rid of the infected limb. Be sure to practice sanitation-pruning methods. The spores from the infected tree can easily transfer onto your tools only to infect a healthy tree or limb.

Scale

Scale

Insect

Trees Affected

Unfortunately, most species of shade trees, fruit trees, and ornamental shrubs are susceptible to damage from scale insects. Ornamental trees such as crape myrtles, camellias, maples, and oaks are particularly susceptible.

Symptoms

Depending on the species of  tree and the kind of scale, the insects may be found on plant stems, twigs, trunks, foliage, or fruit. They often cause the leaves to turn yellow and stunt a tree’s growth. Scale insects damage a plant by sucking out its juice, which causes a reduction in strength and beauty, while introducing other diseases pathogens.

How it Spreads

Scale spend most of their life feeding on the same spot of plant and unable to walk. After eggs hatch, young scales can walk and are called crawlers. Crawlers are very small and move to a spot where they will stay camped out for the spring and summer. Most of them become flat before they cover themselves with a waxy shell or armor. The armor is very difficult to penetrate with insecticides. Some species of scale, called soft scale, do not have protective armor. When the weather turns cold they return to the twigs and bark where they spend the winter.

How To Control it

It is important to know what kind of scale insects you have. It will help determine the kind of treatment you use. Soft scales are a good target for beneficial insects such as ladybugs and wasps. When scale numbers are low, you can rub them off or pick them off by hand. For heavier infestations, prune and destroy twigs and branches.

 

The crawlers are vulnerable to chemical and biological control, and are generally active from late May through June. Horticultural oil will smother the crawlers. Many pesticides are available to apply if you wish to control scale insects yourself. A tree health specialist can help you determine the kind of scale insects you have and how to get rid of them.

Unexposed Root Flare

Unexposed Root Flare

Structural Problem

Trees Affected

All trees can suffer from the effects of an unexposed root flare. Unexposed root flare is by far one of the most common causes for tree decline in urban settings. When the root flare of your tree is not exposed to air, it becomes a breeding ground for fungus, bacterial and insect infestations. The problem can be created from planting a tree too deep or from piling mulch too high around the base of the tree trunk. Groundcovers or vines that surround a trunk can also cause problems associated with unexposed root flare.

Symptoms

Your tree may appear to be declining in health, showing signs of premature leaf drop and eventually branches may die. The circling and girdling roots that form as a result of unexposed root flare can limit or cut off movement of water and nutrients from the root system to the upper portions of the tree.

How it Spreads

Unexposed root flare is a cultural problem and not necessarily a disease that spreads. However, homeowners who do not know how important it is to have an unexposed root flare may perpetuate the problem as other homeowners copy their flawed method of deep planting and piling mulch high against the base the tree.

How To Control it

You, and only you, can prevent unexposed root flare. Be sure the trees in your landscape are not suffering with mulch, soil, or plants hugged up against the base of the tree. You can simply dig around the area until you see where the roots connect to the tree. Leave this area exposed to the air. 

 

If your tree is buried very deep as a result of sediment build-up, or construction activities have piled backfill around the base of the tree, an arborist can help uncover the root flare with an air spade. An air spade is a professional tool capable of removing large amounts of soil around the base of the tree.

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rootFlare Tree Diseases
Is Your Root Flare Showing? Problems of an Unexposed Root Flare

One of the most important ways you can take care of the trees in your landscape is to make sure the root flare—also called the root collar or the buttress of the trunk—is exposed to the air. When the flare is underground or covered by mulch or groundcover plants, the bark can remain moist and unable to breath or respire. This invites bacteria, fungal growth and can lead to rot, even death.

rootFlare Tree Diseases
Is Your Root Flare Showing? Problems of an Unexposed Root Flare

One of the most important ways you can take care of the trees in your landscape is to make sure the root flare—also called the root collar or the buttress of the trunk—is exposed to the air. When the flare is underground or covered by mulch or groundcover plants, the bark can remain moist and unable to breath or respire. This invites bacteria, fungal growth and can lead to rot, even death.

seiridiumCanker Tree Diseases
Tree Cold Sores: The Seiridium Canker

Seiridium, one of many tree diseases, is a cankerous, fungal disease that is found all over the country, just blowing in the wind. Seiridium canker is a major problem on cypress (Arizona, Italian, Leyland) and and Thuja species (also called arborvitae). It can also be a minor problem on junipers.

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