Family Forest Blog

How FFCP Helps with the Invasive Emerald Ash Borer Beetle

Ian Forte, Senior Forester, Central Appalachian Region

September 22, 2023

AFF-Emerald-Ash-Borer

The emerald ash borer is an invasive insect that is detrimental to ash trees.

Many family forest owners turn to a forester for advice on how to locate, treat and manage invasive plant and insect species. Landowners enrolled in the Family Forest Carbon Program benefit from a close relationship with a forester provided to them by the program. Our foresters help them implement a sustainable forest management plan that includes measures against invasive species. Here we share valuable information to help fight against a common and destructive invasive insect, the emerald ash borer.

What is the Emerald Ash Borer

The emerald ash borer is a small, iridescent green beetle, roughly one-half inch long, that attacks ash trees. In the adult stage, it nibbles on ash foliage but does not destroy the tree. In its immature larvae stage however, the insect tunnels through and eats an ash tree’s inner bark, preventing the tree from transporting water and nutrients, ultimately killing the tree. This insect has been found in thirty-five U.S. states and five Canadian provinces and has destroyed millions of ash trees in North America, causing negative financial impact to forest landowners, municipalities, and timber-related industries.

How This Insect Was Introduced

The emerald ash borer is thought to have been introduced to North America in the 1990’s through imported wood packing materials or pallets. It was first detected in 2002 in southeastern Michigan and adjoining Ontario. Then in 2007 the insect was detected in western Pennsylvania. It has spread from this epicenter through natural expansion, with adults capable of short flights traveling up to six miles, and human-mediated transportation of infested firewood and nursery stock.

Impact on Native Plants

Invasive species are detrimental to native ecosystems. The emerald ash borer became an additional problem for landowners after a variety of non-native shrub species were introduced around wetlands of south-central Pennsylvania. The non-native shrubs inhibited native tree regeneration, native plant growth and forest succession. This damage to the ecosystem was compounded by the emerald ash borers’ destruction of ash trees. Additionally, because this insect completes its life cycle on woody species in the olive family, threatened species such as the fringe tree have declined.

Impact on Wildlife

Animals are negatively affected by invasive species as the habitat on which they depend degrades. The loss of ash trees due to an emerald ash borer infestation causes a loss of some native wildlife. Over two-hundred and eighty species of arthropods in North America depend on ash trees as a host, including the waved and great ash sphinx moths and the ash flower gall mite. One hundred species have no or few other host plants. When the emerald ash borer destroys ash, it creates canopy gaps in the forest so numbers of birds and ground beetles decline.

How FFCP Helps Landowners?

Professional foresters provided by the Family Forest Carbon Program help enrolled landowners identify when a forest has been invaded by emerald ash borer. Some of the signs of the insect’s presence in ash trees include D-shaped adult exit holes in the bark and S-shaped larval feeding galleries or tunnels just below the bark. The tree’s upper crown dies and the bark splits and flakes. There can be epicormic branching where new shoots grow from a dormant bud, and because woodpeckers are natural predators of the insect, woodpecker holes may also be visible.

AFF Emerald Ash Borer Marks in a Tree

Dead ash trees may show damage from invasive emerald ash borers below the bark.

Treatment Options

Insecticide treatments applied to ash trees are most effective before infestation occurs. Forests that have already lost over half of their canopy are not likely to recover. Treating ash trees with systemic insecticides is less costly than removing infected or dead trees, and insecticides applied after infestation may stop but will not repair the damage already caused by the insect. Since there are little or no visible signs of early infestation, it is wise to treat your trees if there’s any noticeable damage from this insect within 30 miles of your forest.

Treatment options available to professional applicators include soil injection or drench insecticides that include the active ingredient Imidacloprid that is best applied in early to mid-spring or late fall, and Dinotefuran that is best applied in mid to late spring. Trunk injection insecticides include Azadirachtin and Emamectin benzoate that is applied in mid to late spring after tree leaves appear. Systemic basal bark sprays should be applied in mid to late spring after leaves appear and may include Dinotefuran. Some soil drench insecticides are available directly to landowners and contain many of these active ingredients. Biocontrol options are also under development including the testing of parasitoid wasps.

Treatment Effectiveness and Considerations

The effectiveness of any treatment is based on a number of factors. Biocontrol is a long-term solution but can have damaging effects on ecosystems and should be avoided if possible. Insecticides applied to soil and basal sprays have shown inconsistent results, but if conditions are exactly right, they can be highly effective. Trunk injections applied at the right time of year show excellent results. Only trees that are healthy and are of value to the homeowner should be considered for treatment. Infected trees should be removed before they become a hazard.

If you decide to apply the treatment yourself, no matter what method you use, choose one that suits your needs and comfort level, read all labeling directions and watch videos on proper treatment application. Professional foresters, including those provided through the Family Forest Carbon Program, are always excellent resources for guidance.

How to Protect Against Infestation

It is unlikely that the emerald ash borer will ever be eradicated without universal commitment to treatments. We have far too many private and public forests to address individually. Forest owners will find that inspecting ash saplings regularly to monitor for infection is the best form of protection. Finding early signs of infestation and early treatment is the best approach to preventing and controlling an outbreak.

For more information on the Family Forest Carbon Program, which provides professional forester guidance, a sustainable forest management plan that includes invasive species management, and annual payments, please see https://familyforestcarbon.org/

Ian Forte, Senior Forester, Central Appalachian Region

September 22, 2023

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