Emerald Ash Borer Damage

An invasive species to North America, the emerald ash borer is a green jewel beetle that feeds on species of ash trees. Adults are generally a third of an inch long, .063 inches wide, and a bright metallic green in color. The wing covers tend to be a darker green but can have copper hues. This beetle can be identified from below when it is flying by the upper abdomen, which is bright red.

The exotic beetle was discovered in the summer of 2002 in Michigan, near Detroit. They probably came into the United States in cargo ships or airplanes from their native Asia on packing material of solid wood. As of late 2018, the beetle was found not only in 35 states but 5 provinces of Canada as well. Since its discovery, the borer has killed ash trees in the hundreds of millions in North America, caused quarantines to be placed on logs, trees, and hardened firewood in areas of its occurrence, and cost property owners, municipalities, forest products industries, and nursery operators money in the hundreds of millions.

Emerald ash borer damage appears on largely in green, white, and black ashes. Of the North American species of ash, the blue appears to be the species that is most resistant. The beetle, whose name is often abbreviated to EAB, can also be found feeding on white fringetree. Tree symptoms are typically noticed initially in the top canopy. In fact, by the time a homeowner notices a D-shaped exit hole at ground level from an emerging adult EAB beetle, that tree will probably have been infested by generations of the beetles. Damage is typically quite evident by this point and is visible by watching the upper tree canopy first dying back, followed within the next couple of years by the lower canopy.

Females of the emerald ash borer lay eggs in crevices in the bark of ash trees. Larvae then feed beneath the bark of the ash trees to emerge in one or two years as adults. They exit through D-shaped holes. Adult beetles nibble on the foliage of ash trees but do little damage. The immature stage, or the larvae, feeding on the inner bark causes the true damage. This disrupts the tree’s ability to manage the transport of nutrients and water.

Tree symptoms show as canopy dieback and thinning upon first notice, epicormic suckering and sprouting as the tree is girdled by insect damage, bark cracks and splits, and a high profusion of woodpecker damage as the birds feast on the insect larva. When trees experience stress, they sometimes attempt to grow new leaves and branches where they still can. This is suckering.

Infected trees display top-down dieback with one-third to one-half of branches dying upon first notice; the remaining canopy dies within the two years that follow. This tends to be followed by a great many shoots arising beneath the dead sections of large branches and the trunk. Trees may exhibit two- to four-inch vertical splits within the bark as a response to larval feeding.

Woodpecker predation of EAB larva is another sign of potential emerald ash borer damage in a tree. The splinters of wood from woodpecker feeding tend to be a different color when there is recent damage: a light orange-yellow. The damage will be first noticed in upper branches that have a diameter of three to four inches, but it can be discovered throughout the tree when the infestations are in the advanced stages. Winter is when the damage is particularly visible from the ground level when woodpecker activity is more prevalent. Splinters of wood become more weathered in appearance through late spring and following into the summer months. Extensive damage from woodpeckers is sometimes known as bronzing or flecking.

The issue is further complicated by the fact that these symptoms are not unique to the EAB beetle. Native insects, diseases, and environmental factors may be responsible for symptoms that look identical to those of the EAB. Often common diseases like fungal cankers and verticillium wilt are mistaken for symptoms of emerald ash borer damage.

Specific signs of EAB include D-shaped exit holes that appear in June and July where the adults emerge from the ash trees. The holes are about one-eighth inch wide and may be oriented in all directions. These differ from exit holes of native borers, which will be oval or round and can vary size-wise. Another sign is a series of distinct S-shaped, serpentine tunnels or galleries beneath the bark. The tunnels are about an eighth inch wide and packed with frass, which is a mixture of insect excrement and sawdust. As the larvae feed, trees try to create callus tissue around the galleries. This sometimes causes the bark to split vertically, revealing the galleries and larvae. The final sign of the emerald ash borer infestation is the actual sight of the adults, larvae, or pupae.

Emerald Ash Borer Treatment

A Guide to Emerald Ash Borer Treatment

The emerald ash borer is one of the most destructive species of insect to owners of ash trees. The small, green beetle wreaks havoc on these beautiful trees and it is important to apply comprehensive and effective treatments to properly eradicate them. Since infestation can be systemic causing the species to multiply rapidly, it is important to regularly inspect your ash trees and no what the signs are. If you are able to salvage your ash trees from the destruction, there are thankfully a number of treatment options available.

What Do These Insects Do?

The EAB is an invasive species of insect that primarily lives inside of ash trees, which is the insect’s food source. Discovered in 2002, this species originated in Asia and found their way to the United States where they have decimated all varieties of ash trees and have caused much stress for landscapers and homeowners. The mechanism of infestation begins when females lay their eggs underneath the bark of the trees and the hatched larvae feast upon the trees interior bark, causing the tree to rot from the inside out.

The insect has destroyed millions of ash trees in the United States and Canada alone. The repercussions have been devastating to local home and garden retail stores throughout North America due to wary consumers not wishing to deal with the severity of a possible infestation. Once an infestation spreads throughout the tree, it becomes difficult to salvage due to the destruction of its interior due to the insects feeding.

Treatment Methods: Insecticides

Insecticides are the most popular forms of treatment against invasive insects, however, it can be confusing trying to find the best product. If you have ever experienced the nightmare of cockroach, termite, or bed bug infestation, then you are no doubt aware that insecticides must evolve to keep up with the defense mechanisms of insects. Emerald ash borer treatment is a continuously evolving process and insecticides are at the forefront of that approach.

Treating ash trees with insecticide requires precision since the larvae of the insect maintain a pattern of eating underneath the tree bark. Insecticide treatment should be a two-pronged process where treatment of the adult beetles and the larvae are handled separately. Systemic insecticides are water-soluble insecticides whose mechanism of application involves injecting the soil around a tree or directly injecting the chemical into the tree trunk. Some of these insecticides can be used by homeowners while other types require professionals to administer.

Imidacloprid and dinotefuran are insecticides that can be applied to the soil surrounding the ash tree. These chemicals are absorbed by the tree and work by poisoning the beetles during feeding. Landscaping professionals can administer these chemicals with both accuracy and safety. These chemicals can be administered by spray or injection and offer a comprehensive line of defense against the insects.

Insecticides that are administered through soil or trunk injections are incredibly effective as this allows for the chemical to reach the insects much faster. This process can only be administered by a pest control professional, which is worth the cost if trees are visibly dying. To prepare for this service, it is a good idea to irrigate the ground surrounding the tree as dry soil can drastically limit the effectiveness of the product.

An insecticide spray is a good idea to apply to ash tree foliage to kill adult insects on contact and maintain the killing process through a residual coating. This is the quickest and easiest way to treat ash trees–however, it is perhaps not the most effective. The spray will coat the exterior of the tree and foliage but will take a long time to kill all of the insects, especially the larvae underneath the bark.

Treatment: Tree Removal

The results of insecticides in the treatment of ash trees against these insects have produced mostly positive results. The efficiency of emerald ash borer treatment is dependent upon how bad the infestation is upon discovery and how efficient the homeowner is in providing the most effective course of treatment. The larvae can also feed upon the interior of the tree making patterns where insecticide cannot reach them. Sometimes, alternative methods need to be considered.

Due to the genetic makeup of insects, it is only a matter of time before they develop resistance to popular pesticides. In most cases, if emerald ash borer infestation is caught early, pesticides will adequately save the tree. If the damage has been done, it may be cost-efficient to have the tree removed and start again. Always consult with a landscaping professional to decide the best course of action–since treatment may be a possibility. If needed, they can also remove the infected trees with ease and discuss new options.

If you choose to cut your losses with tree removal and want to start over with new ash trees, start preventative treatment early. Regular inspections of ash trees will alert you to any signs of infestation and will ensure that early detection will help to save your tree. Regular chemical injections by a landscaping professional, either by soil or trunk once per year will keep your tree insect free. Regular inspections by your landscaping company can add to your inspections by also providing preventive and active treatment against any insects found.

In Summary

The ash tree is a beautiful tree that brings joy to homeowners all over North America and even though they are susceptible to these voracious insects, their beauty should be protected. Professional landscaping services offer protection for your trees and can ensure they remain protected with regular maintenance and inspections. Through a selection of chemicals that maintain safety for trees and provide toxicity to the insects, landscaping professionals can combine their experience with the most effective treatment options that will get rid of insects and keep them away. This beetle is moving to more and more states in the country,