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Friday August 18th 2017

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Emerald Ash Borer Fact and Fiction

BY SCOTT VREELAND, Minneapolis Park and Recreation Board Commissioner District # 3

I am concerned about the spreading of some misinformation about Emerald Ash Borer. I see the results of that misinformation in a recent post from the Powderhorn Issues list:

“Every ash tree in Powderhorn Park is scheduled to be cut down as a “preventative” measure, 15 percent per year, whether they are sick or not. Why not improve the health of the soil around the ash trees, making them more resilient in fending off the ash borers? You could do that for a lot less money then hiring cruise to cut the trees down! Is it too late to influence these decisions??”

The idea that there is some- healthy soil- “miracle cure” for EAB using compost tea or extract is a false and misleading claim that is a great example of bad science. Unfortunately there has been an infusion of bad science in some recent tree discussions. Bad science is an attempt to apply a  conclusion, that has no verified basis in fact, as truth.

A few words about Emerald Ash Borer and how it is different from other  trees diseases and infestations… Agrilus planipennis, is an exotic beetle  that was discovered in southeastern Michigan near Detroit in the summer of  2002. The adult beetles nibble on ash foliage but cause little damage. The larvae (the immature stage) feed on the inner bark of ash trees, disrupting the tree’s ability to transport water and nutrients. It is a metallic emerald  green beetle that borers into ash. EAB will kill all ash in Minneapolis unless they are constantly treated with pesticides. There is no inoculation or one-time treatment. If you stop treatment ash will become infested.

The Minneapolis Park and Recreation Board has chosen a 8 year phased  removal and replacement strategy over having ash trees that can only exist by  being constantly filled with non selective systematic insecticides.

I realize that there is someone local who is saying healthy soils would make healthy trees that would be resistant to EAB. Unfortunately that is not true. Unlike some other threats to trees that are related to tree health or decline, the Emerald Ash Borer is quite attracted to healthy trees. It may be that the healthier the tree the more attractive it is to the little flying pest. They need a viable vascular system to reproduce.

It is difficult to see trees removed, but: “EAB kills ash trees. All ash trees are susceptible to EAB and millions of ash trees have been killed in infested areas already. Minnesota has the highest volume of ash trees in the U.S. with almost a billion forest land and urban wood ash trees”

We are looking at the devastating loss of an entire tree species. The best we can do is to try to slow it down and manage the impact.(and find out if Manchurian ash has some resistance)

If you look at the dynamics of how the timing of EAB infestation occurs, there are a few years of relatively little tree loss and then a sudden spike of almost complete tree loss. We have tried to remove infested trees to slow the spread, but I think we will begin to see that sudden increase and the beginnings of massive tree mortality in the next two years.

I live on an ash tree street that was almost all ash boulevard trees. Several of my neighbors and I have requested to have our ash removed and replaced with a more diverse selection of trees. And because this started several years ago there is now some non ash tree canopy on the block. We are in an infestation hot spot where ash trees will be removed- not as a precaution- but because they are infested trees that will die and fall down if not removed. (One of the best indicators of infestation is woodpecker damage, flecking that occurs when they dig out the larvae)

There are three choices, filling trees with insecticide, doing a phased removal, or waiting until all the trees die at once. The problem with waiting for a bunch of dead ash trees all at once, is that dead ash trees don’t stand as majestic ghosts. It would be an unmanageable mess that would not have sufficient funding for a single year of massive loss. Dead ash trees and branches are brittle and fall down and are dangerous especially in an urban environment if not removed.

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