Emerald ash borer
An adult emerald ash borer.
Minnetonka prepares for Emerald ash borer
The Emerald ash borer (EAB) was discovered and confirmed in St. Paul, Minn., Thursday, May 14, marking the first time EAB has been found in Minnesota.
EAB is a non-native invasive insect from Asia that kills all native Minnesota ash trees. According to the Minnesota Department of Agriculture (MDA) no evidence to date of resistance against EAB has been found in any native North American ash populations. In areas where EAB has become established in North America, ash tree mortality rates approach 100 percent. Insecticide treatments are available that can in some situations protect individual trees from EAB attack. The damaging agent is the immature stage—the larvae—of the insect.
An emerald ash borer larva feeds on a tree.
The larvae kill ash trees as they feed on the living tissue under the bark. Sometimes the symptoms can be very subtle. Contact a local consulting certified arborist for an inspection and treatment options. Timing is crucial to any treatments and trees that are already infested may not survive.
The US and Minnesota Department of Agriculture (MDA) are the lead agencies handling EAB. These agencies worked with the city and volunteers to delimit the boundaries of the infestation in St. Paul. Because the insect is so difficult to detect, once EAB is detected in an ash tree, it has likely been in an area for three to five years.
Left to their own devices, EAB spread at a rate of ½ to two miles per year. However, the human spread of firewood and goods has accelerated the rate at which it is establishing in new areas. The mature beetles can fly two to six miles in its short three-week life span.
The city of Minnetonka has been participating in the MDA’s voluntary early detection program for the last three years, and will continue to cooperate with the lead state and federal agencies in order to help control the spread of the insect. While EAB has not yet been detected in Minnetonka, the city is taking action now to prepare a comprehensive plan in order to effectively manage the pest once it arrives. The plan will include sections on topics such as prioritizing ash tree removals on public property, budget impacts, replanting, and wood waste considerations.
At this time, the city encourages residents to learn more about EAB, its symptoms and its common insect “lookalikes” by visiting two main Web sites: the Minnesota Department of Agriculture and the University of Minnesota Forest Resources Extension.
EAB has not been detected yet in Minnetonka, but some residents are choosing to contact a certified arborist working for a private company. They can look for signs and symptoms of EAB in your ash tree, and evaluate whether it would be a good candidate for preventative treatments. Many homeowners want to know whether or not they should start to protect their ash with chemical treatments. A general guideline to use is if trees are within 10–15 miles of the current infestation in St. Paul, homeowners should consider treating their ash if they plan to protect them. Most reputable companies employing certified arborists will be familiar with the insecticides available. One is applied to the soil, the other is a stem injection. Since the treatments are pesticides that must be applied every 1–2 years, it is important to evaluate whether or not the tree is worth the investment. Trees should be evaluated for their structural integrity and their overall health and condition before being treated. Some homeowners and land managers will use the treatments as a stop-gap measure to buy them time as a newly planted tree becomes established. The soil drench option should never be used near storm drains or open water. There are many other factors to take into consideration before deciding on treatments, so it is important to look into all your options before deciding on a treatment.
It is not necessary for homeowners to remove healthy ash trees at this time, though you should start diversifying the tree species in your yard if you have mostly ash trees now. View a list of suitable ash tree replacements. The city has a list of tree contractors available on the hiring tree care professionals page, with companies who have certified arborists on staff denoted by an asterisk. Homeowners may also contact the MDA’s “Arrest the Pest” hotline at 651.201.6684 after learning more about the pest. Due to the volume of requests for information, it is important that residents read some information about EAB prior to contacting state and local agencies.
