A well-kept tree can be the crowning jewel of any home garden or municipal park. However, many tree species across the United States are under attack from a variety of diseases, making tree maintenance more of a problem than ever before. If you’re concerned about the health of your trees, read on to learn more about common tree diseases and how you can combat them with the help of an experienced arborist.
1. Ash Trees
Ash trees are natives to many parts of Virginia, providing a habitat and food source for countless native animals. These trees, belonging to the Fraxinus family, are widely popular for both city and home gardens, due in large part to their bright yellow leaves in the fall. They also happen to produce the wood of choice for baseball bats.
The Emerald Ash Borer
Ash tree populations have been under threat across the United States since 2002 when southeast Michigan discovered its first infestation of the Emerald Ash Borer. Originally from the eastern regions of Asia, the Emerald Ash Borer poses little threat to its home environment. In America, however, Emerald Ash Borer infestations can be fatal to a tree within two years. Millions of ash trees die annually, and since coming to Virginia in the summer of 2008, it’s caused a significant drop in the ash tree population.
The Emerald Ash Borer costs property owners and municipalities millions each year, which is why understanding and combating it is essential.
The Emerald Ash Borer likely made its way to the United States via trade with East Asian countries, stowed along in wood packing materials aboard a plane or ship. The adult, a long beetle with a metallic green shell, poses little threat, eating foliage without doing internal harm to the plant.
The white, wormlike larvae, however, feed on an ash tree’s inner layers of bark. When the tree loses this layer, it also loses its ability to transport water and nutrients throughout the tree’s body. If feeding continues throughout the larvae’s growing season, from August through October, the tree may die from the damage caused.
Emerald Ash Borer damage can be difficult to find early on. You may notice small exit holes and snakelike larvae channels under a tree’s outer layer of bark. If you notice any excessive bark splitting or woodpecker activity, this could also be a sign of activity.
The following symptom, seen after the ash borer larvae have gotten to work, is the death of a tree’s uppermost leaves, followed by new growth lower in the tree. This is the tree’s attempt to work around the bark damage. If the damage is extensive enough, the tree can’t make up the lost productivity, and the tree will die.
In the case of an Emerald Ash Borer infestation, you should notify local authorities responsible for pest management and prevention. This helps them know to check the surrounding area for ash borers. The next step is to find a professional to treat the tree. They know how to get rid of an Emerald Ash Borer infestation if the tree is salvageable.
If you note a leaf loss of over 50 percent, however, then it’s unlikely the tree will survive. An arborist can determine what to do in either case. Because Emerald Ash Borer treatment can be hit or miss, prevention is essential. Prevention measures mostly include the use of insecticides. Always consult with an arborist before taking action — they have the expertise you need to implement insecticides appropriately.
Oak trees are majestic, but slow growing. Once fully grown, however, they can function for hundreds of years as great shade, a habitat for wildlife and an interesting feature to anyone’s garden. The one big problem many oak trees suffer from is root rot, which can cut an oak’s life down to mere decades. The most common of these in Virginia are the armillaria and ganoderma root rots.
Armillaria Root Rot
This common fungus is one of the most problematic causes of root rot in oaks, especially in the United States. This disease leaves trees spongy and sickly, taking anywhere from a few weeks to a few years to finally succumb to their illness.
Armillaria root rot is caused by a family of root-inhabiting fungi. The most common of these, Armillaria mellea, is commonly found in warmer regions of the United States. The wet soil found during the summer months encourages the fungus to multiply, spreading to the roots of oak trees.
This fungus is a problem for already stressed trees, as healthy trees can easily fend off the rot. In stressed trees, the armillaria destroys the roots, meaning that the tree can’t absorb enough nutrients to support its daily functions. Their ability to grow and heal suffers, as a result, causing the tree to sprout yellowed leaves. Some more visible signs of the disease include mats of white, fungal threads under the bark of the tree near the roots.
Armillaria is fungicide-resistant, so it’s more important to manage the conditions of the oak tree to improve root health. Oak trees tend to prefer dryer summer conditions, so cutting back the amount of water in the soil may be the best way to prevent root rot before it starts or minimize the spread of the fungus. If the tree is apparently suffering, consult with an arborist to determine the next step.
Ganoderma Root Rot
For oak trees growing in moist soil, ganoderma root rot is a serious issue. Already stressed oak trees tend to suffer more often, but even the healthiest trees can succumb.
This root rot is caused by Ganoderma lucidum, also known as varnish rot fungus. Like the armillaria root rot, it is often found in warmer regions and multiplies using spores during the wetter part of the season, spreading to the roots of trees in the area.
A ganoderma infection destroys an oak tree’s roots, bringing about a significant loss of foliage, yellowing leaves and dying branches. Ganoderma is most defined by white-margined, reddish structures extending approximately 14 inches from the base of the oak.
Treating a ganoderma-infected oak mostly involves removing dead limbs or removing the entire tree to prevent further spread of the disease. Prevention is the most efficient strategy for handling this condition, however. Oaktree owners can accomplish this by avoiding over-watering or damaging the tree.
3. Leyland Cypress Trees
Leyland cypress trees are elegant additions to any garden, providing beautiful green foliage and a rapid growth rate. They’re often used for decoration as screens or hedges. However, these trees are prone to a wide variety of diseases, any of which can brown the foliage and even result in the death of the tree. These diseases are listed and described in more detail below.
The seiridium canker is a common and extremely damaging disease for Leyland cypress trees. Any plant of any age or size can easily die from this condition.
Seiridium cankers are caused by Seiridium unicorne, a fungus that attacks just under the surface of a tree’s bark, forming cankers that can disrupt function in a tree’s nutrient and water flow system. The fungus spreads from one part of an infected tree to another, either from water splash or by coming in contact with pruning tools.
The most characteristic symptom of seiridium canker is the appearance of cankers. These sunken, brown patches of the bark appear everywhere on a tree, causing stems to die and fall off. Any branches killed by the disease turn bright reddish-brown. What defines this form of canker from others is the sheer amount of resin infected Leyland cypress trees secrete after infection.
There are no chemical treatments available for seiridium canker at the moment, so prevention is highly recommended. Avoiding overwatering or wounding Leyland cypresses is by far the most efficient of these prevention measures. If a tree is already infected, infected branches should be removed as soon as possible, and equipment sterilized. If the plant is too diseased to save, then it must be removed and destroyed before the disease spreads.
Botryosphaeria canker looks very similar to seiridium canker and can be just as devastating. Here’s everything you need to know about this Leyland cypress disease.
This canker fungus is caused by Botryosphaeria dothidea, which takes advantage of the wetter weather in early summer by spreading through water droplets from one tree to another. They can also be spread by the wind.
Like seiridium canker, botryosphaeria canker can be identified by the appearance of scattered bright reddish-brown dead twigs and branches throughout an otherwise healthy tree. These cankers are dark in color and sunken, much like botryosphaeria cankers, but they do not produce excess resin. Additionally, botryosphaeria is characterized by uniquely long, narrow cankers on the trunk of the tree.
Experienced arborists know how to save a dying Leyland cypress tree in most cases — usually, it involves pruning and destroying dead branches. However, extensive cases of botryosphaeria canker can result in removal of the tree. For this reason, prevention is essential for a Leyland cypress tree owner to consider. Healthy, appropriately watered plants are more resistant to botryosphaeria, and avoiding heavy fertilization or pruning can keep them that way.
Cercospora Needle Blight
Needle blight is a relatively new disease to the Leyland cypress, more commonly found on other tree species. However, this fungal disease can still be deadly to a young Leyland cypress.
This blight is caused by the fungus Cercosporidium sequoia. This fungus grows best during wet periods and spreads using the wind throughout the spring and summer. This allows it to spread quickly, affecting large groups of trees all at once.
The first symptom of blight is browning in lower needles of the tree. The disease spreads upward, leaving only the uppermost needles in late-stage cases. This may look like normal stress, but close inspection should also reveal green fruiting bodies of the fungus appearing on the needles and twigs throughout the spring and summer.
Needle blight is best controlled using a spray of copper-containing fungicides. Spray plants throughout the growth season every ten days to prevent Leyland cypresses from turning brown after planting. If the infection is more widespread, a professional arborist will know how to save a dying Leyland cypress tree.
Annosus Root Rot
Though far from the Leyland cypress’ only root rot problem, annosus root rot is most likely to lead to browning. This form of root rot is common among landscape plants.
Annosus root rot is caused by the fungus Heterobasidion annosum. This type of rot affects landscaped trees by infecting new stumps and sinking into the roots. Once in the roots, the fungus spreads to the roots of other trees
The most notable symptom of annosus root rot is the browning of the leaves. The tree may show such symptoms slowly or all at once. In later stages of the illness, the entire plant becomes a reddish-brown color.
There are no chemical cures for this type of root rot, and destroying an infection entirely often means removing and destroying the infected tree. For this reason, prevention is essential for Leyland cypress owners. Treat fresh stumps with granular borax after cutting if they can’t be immediately removed, and ensure the soil drains properly. When in doubt, contact a professional arborist for prevention and treatment plans.
Phytophthora Root Rot
Phytophthora root rot poses a problem for nursery and landscape trees, especially ones with smaller roots. This fungal disease is especially problematic during wetter seasons and in more humid environments.
This form of root rot is caused by Phytophthora cinnamomi, which is spread from stump to stump when infected plants are felled. The fungus grows through the stump and the root system to infect nearby trees and rot the root.
As with many root diseases, upon infection with the disease, the tree experiences a general yellowing of foliage. After the roots have undergone enough damage, the entire tree may turn a red-brown color and eventually die off. The best way to tell this rot from others is the small brown fruiting bodies that grow at the tree’s base.
This type of root rot can only be diagnosed using laboratory tools, and it can’t be cured once a tree is infected. Instead, an arborist must remove the tree using appropriate fungicidal measures. Since it cannot be cured, preventative measures are the best ways to control phytophthora root rot. Keep soil relatively dry and try to use mild fungicidal measures when feasible.
4. Hemlock Trees
Hemlock trees are graceful additions to any landscape, but they require precise conditions to thrive. Without proper care, they can die off from one of many diseases. The most common of these disorders are described in more detail below.
Hemlock Woolly Adelgid
The hemlock woolly adelgid is a type of insect, first found in Virginia in the early 50s. Since its introduction, its habitat has taken over a large portion of the United States. Once infected with this disease, hemlocks die within a decade, sooner if they’re already living under severe stress.
Native to Asia, the hemlock woolly adelgid is an aphid-like insect that is reddish-brown to purplish-black in color with a slightly woolly appearance. Their larvae, however, are the primary problem. These tiny crawling insects feed on the starch reserves of the hemlock, which is how these plants survive in winter. Without their stores, the tree dies. These insects feast on hemlock trees of all species.
Leaf death is the most significant sign of a hemlock woolly adelgid infestation. The infestation will often result in off-color needles that turn a grayish color. The way to distinguish this infestation from others is by looking at the twigs of the tree — infested branches will have white woolly egg sacs deposited along the twig below the needles.
Both chemical and biological control options are available for Hemlock Woolly Adelgid treatment. Insecticides can be effective for smaller-scale infestations, while biological controls are currently being studied for more widespread control. However, prevention — primarily by moving bird feeders away from hemlocks and removing infected trees from a lot as quickly as possible — is the best way to combat the woolly adelgid. Contact an arborist if you need help with your hemlock’s woolly adelgid infestation.
Contact All Natural Tree Experts
At All Natural Tree Experts, we want to provide the best tree treatment services for Roanoke, Virginia and the surrounding area. We work with both commercial and residential customers, offering expert advice and service for trees of all kinds. Our team of certified arborists can do everything from limb and stump removal to chemical treatment. We’re so dedicated to your satisfaction that we even offer 24/7 emergency services.
Choose the best tree treatment company in Roanoke Virginia. Contact All Natural Tree Experts today for a free estimate.