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While the adult EAB beetle only nibbles on ash foliage, causing little damage, the problem lies with the larvae. Female borers lay their eggs underneath an ash tree’s outer bark. As the larvae grow and mature, they tunnel and feed on the tree’s inner bark, destroying its xylem and phloem tissue. This disrupts the tree’s ability to transport water, mineral nutrients and photosynthetic sugars to all parts of the tree, eventually killing it.
Multiple species of borers exist in addition to EAB. Borers, in general, will primarily attack only unhealthy or stressed host plants. In its native range, EAB works in a similar manner. However, since our native ash trees do not have any inherent defenses against EAB, all species of ash trees in Minnesota, whether healthy or not, are susceptible to destructive attacks.
Minnesota has the third largest population of Ash trees in the country. In urban areas, the Ash tree became the predominant “replacement” tree when trees were lost to Dutch elm disease. The Ash tree is also vital to many natural areas throughout the state.
In Edina, the Ash population is estimated at 50,000. The most valuable Ash trees (based on size, health, location and landscape importance) are primarily situated on residential lots, some parkland and a few boulevard areas throughout the City. An outbreak could greatly affect the City’s tree population.
Chemical treatments are available to help protect healthy Ash trees or those minimally affected. If you choose to use chemical protection, keep in mind that application must take place every two to three years, depending on the chemical and application method used, and can be somewhat expensive.
The decision to commit to long-term use of chemical protection is a private one, but some factors to consider are the relative importance and health of the tree or trees in your landscape and the affordability of a long-term commitment. As with all trees, Ash trees have multiple potential blights or diseases that will not be helped by EAB protection.
The City Forester recommends people with Ash trees contact a private arborist or tree care company to evaluate their options. He discourages the use of store-bought treatments that you spread on the ground to protect trees from Emerald Ash Borer. These may contaminate the surrounding soil and spread into groundwater or run off into nearby streams or drainages. They also can harm pollinators. Arborists inject trees directly, a method that is believed to have fewer concerns for water quality and is less likely to spread chemicals to water bodies, animals, insects or surrounding plants.
Another management option - also widely suggested for Dutch elm disease - is to consider planting another tree or trees on your landscape to have a replacement in the event you lose an important Ash tree. This option can be considered whether or not you also choose to chemically treat an Ash.
Residents are strongly encouraged to learn more about the disease in order to respond in a well-informed manner based on the latest factual research.
It would be inappropriate for the City to promote a particular tree company or arborist.
However, the Minnesota Department of Agriculture has a checklist for hiring a tree care company and a license information search (select Tree Care Registry as the license type) to assist in finding one.
Ramsey and Hennepin counties are currently under Department of Agriculture quarantines in regard to the movement of ash wood. EAB has a wider spread when infested wood is moved. If purchasing firewood, be certain it is not infested with EAB.
Do not transport firewood to or from another county.