Prevent your Georgia trees from falling victim to killer pests and diseases. By knowing how to identify a distressed tree and its cause, you can take measures to keep it alive and protect surrounding trees.
georgiatreecare.wordpress.com gathered information on common tree pests and diseases found in Georgia, how to treat them, and how to prevent them.
Protecting Your Georgia Trees
Georgia tree species have spent millennia evolving and adapting to climate change, aggressive tree pests, and invasive diseases. While trees are highly effective at protecting themselves, your ability to detect potentially devastating pest infestations and diseases can aide in the preservation of Georgia’s tree population.
The following are pests and diseases commonly found to afflict Georgia tress:
Pine Bark Beetles (SPB, BTB, and Ips)
Pine bark beetles are among the most destructive insects affecting pines in the State of Georgia. They occur across all land types and geographic regions of the state. Since 1962 annual losses from pine bark beetle outbreaks have exceeded $5 million in the state.
The species most responsible for infesting Georgia pines include:
- SPB – Southern Pine Beetle
- BTB – Black Turpentine Beetle
- Engraver Beetle – Ips Beetle
Adult bark beetles are about 3/32″ in length and reddish-brown to black. Trees are affected and killed when thousands of adult beetles bore beneath the bark to feed and lay eggs. Fungi are carried from tree to tree by the beetles. These fungi invade the water-conducting tissues (xylem and phloem), causing hydraulic failure. This results in the needles drying more rapidly.
Signs and Symptoms – Signs of beetle attacks include:
- Pitch tubes
- Boring dust
- Needles will turn yellow-green, then red, then brown
The time it takes for needles to begin fading after a beetle attack can range from 2 weeks (attacked in the summer) to 2 months (attacked in early spring or late fall).
Affected Species – Pine bark beetles attack all species of southern yellow pines (sapling, pulpwood, and timber size). It is extremely destructive in mature and crowded stands. Infestations are often fueled by droughts, flooding, lightning strikes, and human disturbances.
How It Spreads – Adult beetles take flight and move from tree to tree. These beetles are more successful when mounting attacks on trees in decline or stressed from other factors. Healthy trees may also become infested after multiple attacks reduce the effectiveness of their defenses.
How To Treat It – Pine trees that have been successfully attacked by beetles cannot be saved by applying an insecticide to the bark or by injecting the substance into the tree. Homeowners should beware of persons advocating using chemicals to control any species of pine bark beetle.
The most effective step in stopping a beetle infestation is to remove and destroy all infested trees. Remaining healthy trees can be treated and protected by applying an approved insecticide to the tree’s outer bark (on the entire tree).
The best treatment against bark beetles is to prevent them. You can accomplish this by:
- Promoting the health and vigorous growth of your trees
- Treating the bark of your trees
- Removing and destroying infested trees
- Immediately remove trees after being struck by lightning
- Reporting suspected infestations in your area
As pines reach maturity and continue aging, their susceptibility to bark beetles steadily increases. In regions where outbreaks are confirmed, these trees must be protected or removed to slow or halt the beetle’s spread.
Emerald Ash Borer (Agrilus planipennis)
The Emerald Ash Borer (EAB) belongs to a group of metallic wood-boring beetles. Unlike Georgia’s native beetles that infest and kill weakened trees, emerald ash borers attack and kill vigorously growing and weakened ash trees. EAB is not native to the United States and was first found in Michigan in 2002.
The July 2013 discovery of Emerald Ash Borer (EAB) in Georgia prompted a regional quarantine which, by 2017, resulted in the quarantine of the entire state. This quarantine regulates and restricts transportation of the following:
- Emerald Ash Borer in any of its life stages
- Firewood of all hardwood species
- Ash nursery stock
- Green (non-heat treated) ash lumber
- Any living, dead, cut, or fallen material of the tree genus Fraxinus, including logs, stumps, roots, limbs, and composted and non-composted chips that have not been ground to a small enough size to destroy EAB in any of its life stages
Characteristics and habits of the EAB include:
- Adult EAB are bright, metallic, and emerald green in color
- They are less than 1/2 inch long and feed on ash foliage, although that damage is typically minimal
- EAB larvae feed on the inner bark of ash trees, impeding a tree’s ability to transport water and nutrients, killing the tree
- Larvae tunnel S-shaped galleries on trees
- There may be bulging and vertical splitting of bark over larval galleries
- EAB adults make D-shaped exit holes on the bark of infested trees
Once an ash tree is infested by EAB, it will most likely die. Ash trees have little to no defense against this tree killer. For this reason, even the healthiest, most vigorous ash trees can be successfully attacked and killed.
Signs and Symptoms – When an ash tree is successfully attacked by EAB, symptoms are quick to appear and include:
- Canopy dieback starting in the top of the canopy and spreading until the tree is bare
- Growth of epicormic shoots (sprouts growing from the trunk and roots)
- Large holes left by woodpeckers foraging for larvae and pupae
- Bulging areas of bark with vertical splitting (over galleries)
If you suspect an EAB infestation, find and contact your local County Extension Office at caes.uga.edu/extension/office.cfm or your local Georgia Forestry Commission Office at gfc.state.ga.us/about-us/contact-us/county-units/index.cfm
Affected Species – As the name suggests, EAB attacks ash species including:
- Green ash (Fraxinus pennsylvanica)
- Black ash (Fraxinus nigra)
- White ash (Fraxinus americana)
- Blue ash (Fraxinus quadrangulata)
EAB has also been found infesting non-ash hosts such as white fringe tree (Chionanthus Virginicus) in North America.
How It Spreads – After adults emerge from their host, they proceed to the tree’s canopy and feed on the tree’s foliage. Males will hover around the trees in search of females to mate with. Mated females will then lay eggs, on the same or new host tree, between bark crevices, flakes, or cracks.
After eggs hatch, larvae chew through the bark to reach the phloem and xylem layers, where they feed and develop, starting the insect’s lifecycle again.
How To Treat It – Once infested, there are no known treatments, and the tree will need to be removed and destroyed.
Under normal circumstances, promoting the tree’s health and vigor is the first line of defense for trees. In the case of EAB, this is not enough. Ash trees have no defenses against an EAB attack.
Insecticides can be applied to ash trees by direct application, injection, or soil drench as a preventive measure. These insecticides should only be administered by licensed applicators and do not guarantee the tree’s safety or preservation.
If you suspect an EAB infestation or have become aware of a nearby infestation, contact an ISA certified arborist to evaluate your landscape and present a course of action to preserve your trees.
Dutch Elm Disease (Ascomycota)
This is a vascular wilt disease that has decimated the country’s elm tree (Ulmaceae family) population throughout the last century.
In 1930, a Dutch scientist, Christine Johanna Buisman, first identified DED in Ohio. The disease then spread up and down the US east coast and then across the continent, until reaching the west coast in the early 1970s. Tens of millions of American elm trees have perished to this disease. Today, DED continues to be a destructive disease of all elm tree species in the US.
Signs and Symptoms – Once the symptoms of DED appear, fast action must be taken to contain the disease. Consider the following:
- Yellowing and wilting of leaves on individual branches
- As branches die, the leaves curl up and turn brown
- Dead leaves may remain attached to the tree
- Initially affected leaves are at the extremity of the crown
- Progression of the disease causes the entire crown to show symptoms
- Sapwood discoloration
Trees infected with DED via beetle vectors will likely develop initial symptoms in the crown’s upper extremities. Trees infected by the disease via root grafts first develop symptoms in the lower parts of the crown.
Note: When the disease is introduced through a root graft, it can be quickly distributed throughout the tree’s vascular system. When this infection method occurs in early spring, a completely healthy elm can decline and die by mid-summer.
Tip: Other wilt diseases that affect elm trees, such as Verticillium wilt, also cause similar foliar symptoms and sapwood discoloration. Positive DED diagnoses should be made by laboratory examination.
Affected Species – All US native elm species are vulnerable to DED, including:
- American elm (Ulmus americana)
- Red or slippery elm (Ulmus rubra)
- Rock elm (Ulmus thomasii)
While this may seem like a bleak prognosis, hybrid elm species are being produced that are resistant to DED.
How It Spreads – Carried by bark beetles primarily, here are the beetle species most likely to spread DED:
- Elm bark beetle (Hylurgopinus rufipes)
- European elm bark beetle (Scolytus multistriatus)
- Banded elm bark beetle (S. schevyrewi)
Adult females of elm bark beetles lay eggs under the bark of recently dead or dying trees, or in cut wood. Larvae then feed on the inner bark and sapwood of the tree, creating galleries as they feed.
If the attacked tree is infected with or was killed by DED, spores will be present in the wood. When these beetles emerge as adults from infected trees, they come carrying spores of the fungus in and on their bodies.
As beetles move on to healthy elms chewing through the bark, spores are knocked off the beetle’s body within the tree, starting a new DED infection.
When elm trees grow in close proximity, DED can spread from an infected tree to a healthy tree via grafted roots.
How To Treat It – Treating DED is tricky, to say the least. Several thorough inspections of all elm trees in an area must be performed during every growing season. Infected wood or trees must be aggressively pruned or removed, burned, chipped, or buried so it cannot house beetle vectors.
Likewise, for elms planted in rows or within 10 to 15 feet of one-another, steps must be taken to break and prevent root grafts between these trees.
Chemical management of Dutch elm disease can be used to protect elm trees of high value. Such fungicides are costly and should be administered by a licensed tree service professional. This tree company can help with tree health assessments, tree removal, and pest or disease treatments:
Note: Chemical treatments are used mostly as a preventive measure.
When opportunities to plant or replant present themselves, select disease-resistant elm cultivars. Elm breeders have spent decades to produce hybrid and clonal elms resistant to Dutch elm disease. Educate yourself and learn more about tree planting and care before planting the above species in Georgia.
Seiridium Canker (Seiridium Unicorne)
In Georgia, Seiridium canker is one of the most prevalent and destructive diseases affecting Leyland cypress in the general landscape.
While the fungi Seiridium cardinale, Seiridium unicorne, and Seiridium cupressi have been reported to cause diseases on Leyland cypress and other needled evergreens, only Seiridium unicorne is associated with cankers and twig dieback. Leyland cypress specimens of all sizes and ages can be adversely affected by the disease in the landscape.
Signs and Symptoms – Seiridium Canker symptoms are most likely to appear in early spring can be seen at any time of the year, and may include:
- Yellowing or browning of the foliage on one or more top or lateral branches
- Formation of numerous thin, elongated cankers on stems and branches
- Cankers cause twig and branch dieback
- Cankers are slightly sunken, with raised margins, and discolored dark brown to purple cracked bark in infected areas can be accompanied by extensive amounts of resin flowing down diseased branches
- Cambial tissue beneath oozing area will be reddish to brown in color
Disease expansion will often continue until a significant portion of the host tree is dead.
Affected Species – Seiridium cardinale, Seiridium unicorne, and Seiridium cupressi all affect multiple needled evergreen species in the cypress family, including:
- Cryptomeria japonica
However, cultivated Leyland cypress (Cupressus × leylandii), often referred to simply as leylandii, is most affected.
How It Spreads – When overhead watering and rainy weather, fruiting bodies of the disease release spores spread by splashing water. This water splashes and travels, carrying the infection to open wounds on stressed trees. Infection on multiple branches of a tree or on the trunk can kill the entire tree quickly.
How To Treat It – This fungus survives in infected bark tissue. Once the disease is confirmed, prune and destroy all infected branches 3 to 4 inches below the affected area. If the disease is present on the trunk, consider removing the tree altogether.
After pruning or removal, sterilize all equipment after use on an infected tree with a 10% bleach or a 70% alcohol solution to prevent the spread of this fungus.
Prevent winter-related damage by:
- Multiple deep waterings in late fall
- Cover trees with burlap
- Mulch the root plate to prevent ground freeze
Promoting your tree’s health and preventing damage of any sort will help you keep your tree healthy and disease-free.
Currently, there are no fungicides proven to be highly effective in controlling this disease.
Georgia Tree Pest And Disease Prevention
In this article, you discovered several tree-killing pests and diseases found in the state of Georgia, how to identify them, treat them, and prevent them.
By knowing how to identify and treat pests and diseases, you can take swift action to save your tree and prevent pests and diseases from spreading throughout your neighborhood.
When you ignore the signs of a tree in decline, you risk losing your tree quickly and spreading the disease or pest to your entire landscape and beyond.