Emerald Ash Borer, Increasing Awareness of the "Green Menace"

Byline: Tony Bratsch, Extension Educator, Horticulture

During May, Governor Blagojevich announced an "Emerald Ash Borer Awareness Week" for the State of Illinois. This action underscores the concern about this new, invasive insect. Emerald ash borer (EAB) is an exotic beetle species from Asia, first found last June in the Chicago region. It is suspected that the insect came to Illinois on firewood from Michigan, where it has been a problem since 2002. In Michigan it was likely introduced in wooden shipping materials from Asia. This insect attacks all species of ash (Fraxinus spp.), inflicting damage by larval feeding in the sapwood of these trees. Within a few years the tree is killed by the extensive tunneling of the larvae under the bark.

With the recent introduction of this insect to Illinois and the so far isolated occurrences in Chicago suburbs, should those of us in the rest of the state be concerned by this invasive insect? Given our current knowledge and understanding of this insect, the answer is a resounding yes! Considering the damage this insect has done in other states, every community and landowner should to be aware of this insect threat. It is important to understand the damage it can do, the current status of the insect and response by government agencies, and lastly what communities and people in the state can do to help reduce spread of this insect.

According to experts, this beetle has the potential to decimate ash trees across the continent. In Michigan it is believed that 15-20 million ash trees have been lost, with losses also occurring in neighboring Ohio and Indiana. Parks, greenways, street and residential ash trees have been destroyed by the thousands. In Illinois, approximately 20-25% of trees in the landscape are ash, with the majority being green or white ash, as well as horticultural varieties. In forests across the state there are an estimated 130 million ash trees that help make up the timber economy.

Probably of greatest concern to communities and individual homeowners is the potential cost of tree removal and replacement in the landscape as ash trees are killed. Where this insect is found, state mandated removal of the tree is required at local and individual expense. Currently the state is helping to pay for the cost of tree removal in affected areas near Chicago, but it includes only symptomatic trees within a half mile of confirmed EAB infestations. How long funding will continue for tree removal assistance is unknown.

Given the proximity of problems in Michigan and Indiana, the arrival of this invasive species was well anticipated and planned for in the development of a taskforce several years back by the Department of Agriculture and other cooperating groups such as the Morton Arboretum and the University of Illinois. Assisted by the USDA APHIS (Animal, Plant Health Inspection Service) program, a joint federal and state plan is now being implemented to eradicate the insect, or at a minimum contain the outbreak.

Currently there are both interstate and intrastate quarantines on movement of firewood and ash products such as nursery stock and green lumber. Firewood transport is a major concern, as the larvae are found in the wood for most of the insect's life cycle – late summer through the following spring. With the large number of trees killed in Michigan, firewood is now abundant there. Even though it is against the law to transport it across state lines, there is a high demand and price for firewood in the Chicago region and it is critical that interstate transport of firewood be regulated. Also campers to Michigan may unintentionally bring firewood back with them. Thus the commercial firewood industry, and the campers and tourists that cross in and out of our state daily represent a significant risk of spread to any location in the state. Regulation and control is difficult at best, but increasing public awareness of firewood transport hazards is by far the most important aspect of the campaign against EAB.

EAB has earned the nickname "Green Menace" because of its bright metallic green color and the threat it represents. Adult EAB are small, narrow, linear insects, and less than a half inch in length. They begin to emerge from limbs and trunks of infested ash trees in late May into July. As they emerge, they leave a distinctly "D" shaped, 1/8" hole in the wood. Adults feed lightly on foliage, mate and deposit eggs on the tree bark. Larvae hatch in about a week and quickly burrow into the trunk. EAB is attracted to weakened ash trees, but will also lay its eggs on a healthy tree of any size or age. It takes up to 3 years for large trees to show larvae feeding symptoms, and by that time it is too late to save the tree. Typical symptoms include top dieback in older trees, and on younger trees, premature leaf yellowing and drop in the fall. When advanced, sprouts or suckers will form on the lower part of the tree. Bark will eventually split and can be peeled away, revealing "S" shaped feeding galleries created by the larvae.

Other than woodpeckers which like to feed on the larvae, there are no natural checks and balances for EAB because it is not native to the US. Control by using insecticides has been shown to be only partially effective, and expensive. These treatments are preventative and not curative, and involve regular systemic trunk injections or root drenches. Foliar sprays are generally ineffective because adults can emerge over a long period during the summer and larvae cannot be reached once they burrow into the bark. Research is continuing with insecticide treatments, as well as identifying potential biological control agents.

EAB is not a long distance flyer like many insects, and on its own will spread only a half to several miles a year. Thus it could be many years before forests are threatened downstate. However, this does not account for the influence of man and accidental introduction, making it possible for this insect to appear anywhere in the state. Thus restricting firewood and ash nursery product transport is critical to containing this insect.

It is possible that infestations may be occurring in the downstate region, and surveys are being planned in areas outside of the Chicago area. Land and homeowners across the state are encouraged to inspect ash trees on their property for signs of EAB, and report suspicious trees to the Illinois Department of Agriculture hotline: 1-800-641-3934. There is also a national EAB hotline number: 1-866-EAB-4512. Locally, contact your county's U of I Extension office to report sightings or obtain assistance with evaluating symptomatic trees.

The future of our ash forest and landscape trees hinges on successful control of the Emerald Ash Borer. Communities and local governing bodies are encouraged to begin planning for the potential arrival and management of this insect. Recommendations include:

· Conduct a thorough inventory of all trees in the community;

· Evaluate the health of all trees in community, especially ash trees, and examine them for symptoms of EAB-infestation such as decline, crown die-back, D-shaped exit holes, excess woodpecker damage, basal sprouting, and larval galleries;

· Remove diseased or declining ash trees and conduct bark-stripping activities on those trees to detect larva and / or their galleries;

· Adopt a diversified species reforestation strategy whereby newly planted trees are made up of a number of different species rather than only one or two species, and avoid planting new ash trees;

· Review tree limb and branch collection programs and determine where such materials are currently being disposed of – if you are located within an EAB-quarantined area, make sure that any contractors or disposal yards have a current IDA EAB compliance agreement in place; and

Increasing awareness of this important insect threat is vital to state and community economies, and to Illinois land and home owners. For additional information and identification techniques for EAB infestation, visit the multi-state collaborative website: http://www.emeraldashborer.info/

or the Illinois Department of Agriculture website for the latest state updates and developments: http://www.agr.state.il.us/eab/.