WORKSHOP ITEM Jon Haukaas, Director of Public Works
Title
UPDATE ON THE CITY OF BLAINE EMERALD ASH BORER MANAGEMENT PROGRAM
Background
Agrilus planipennis, or Emerald Ash Borer (EAB), is a non-native insect transported from Asia to the US and identified in Michigan in 2002. EAB feeds on the tissue of ash trees between the bark and sapwood and disrupting the nutrient and water flow of the tree, eventually killing the tree after several years of feeding in the trees.
Emerald Ash Borer was first discovered in Blaine in March of 2017. It was located in the north central area of Blaine, near Carrara West Park. Since that discovery, we have found infested trees in every corner of the City.
Ash trees were a very popular tree to be installed with development in the 1970s and 1980s and so we have a major population of them. It is estimated that there are 3,000-5,000 ash trees in the boulevard areas, 8,000-10,000 ash trees in our city parks, and somewhere in the range of 50,000-70,000 ash tree on private property in Blaine.
All ash (Fraxinus Sp.) trees native to Minnesota are susceptible to infestation by EAB. Trees become infested when adult beetles lay eggs on the bark, which hatch into larvae that bore into the tree. The larvae tunnel in the vascular tissue of the tree and disrupt the movement of water and nutrients, eventually killing the tree. EAB prefers trees under stress, but is capable of killing perfectly healthy trees as well. Adult beetles emerge from the tree and are capable of flying up to a half mile to infest new trees. New infestation centers also can start by transporting firewood infested with EAB.
City of Blaine’s Current Management Strategy
In anticipation of the arrival of EAB, the City has been proactively removing ash trees since 2009. This management option is known as sanitation. Sanitation involves removing the ash trees and replacing them with different species of trees. Due to the extreme number of trees throughout our urban forest, this is the only economically feasible option for the city.
To date, we have removed hundreds of boulevard and park trees. We have been offering to remove a property owner’s boulevard ash, grind the stump, and restore the grass. We also offer to replace their boulevard tree. This removal program is completely voluntary, and comes with no cost to the property owner. If a property owner chooses to keep their boulevard ash, we encourage them to have the tree chemically treated, as it will eventually become infested if left untreated.
There are very effective chemical treatment options. Companies can inject ash trees with a chemical that will protect ash trees from getting EAB. The treatments are so effective that many companies guarantee protection from EAB. The costs of the treatments are approximately 12-15 dollars per inch of diameter measured at 4.5 feet above the ground. On average, a two foot diameter tree will cost as much as $360. The treatments must be applied every two or three years, for the life of the tree, to maintain protection.
Many Cities have adopted different strategies for managing EAB. Some treat their ash trees, and some have used sanitation, while others have done a combination of both. Some Cities have offered to pay a portion of a resident’s cost to treat their trees as an incentive to get them treated. We could possibly secure a lower rate for treatments if we have companies bid on injecting trees exclusively for the City of Blaine. The City of Andover has successfully implemented a similar program. We would only recommend this strategy for trees deemed significant to the City, such as in Town Square Park.
Policy and Ordinances
The City of Blaine does not have an EAB ordinance or formal policy. In addition to authority to order hazardous trees to be removed, City ordinance allows the City Forester to condemn any tree that is infested or infected, and require it to be abated. Private trees identified as having EAB have been marked, and the property owner notified.
Any policy or ordinance regarding EAB should only target trees that have the potential to become hazardous. A hazard tree is one that poses eminent danger to people or property. Trees killed by EAB dry out quickly and become hazard trees in less time than after a normal tree death. Trees in open space or out in the woods should be left for nature to run its course. Removing trees in remote locations will have no impact on slowing the spread of EAB.
Outlook
Now that EAB has been discovered in Blaine, we anticipate a steep increase in ash trees dying from this insect in the future. We could be looking at thousands of trees dying every year. We need to continue our removal efforts, and will need to increase our efforts as the urban forest become more impacted by the spread of the disease.
Recommendation
Provide feedback on the current approach to EAB management.