Infestation

Pests come from different sources and in different sizes and shapes.  The pest I wish to talk about today is an invasive specie that made its way from Asia to the United States.  The emerald ash borer (EAB) was first noticed in central Michigan in 2002 and likely came over as part of wood shipping crate by sea or air from northeast Asia, much of it being northeast China and part of Mongolia.  As a child I recall the street trees being taken down due to Dutch Elm disease, so we are in a situation that is now repeating itself, but with a different pest from a different part of the world.  With the EAB many cities, such as my current village, took trees down ahead of the anticipated infestation. The EAB was first noticed in Wisconsin, the southeastern part of the state, in August 2008.

Injection lines connected to the tree awaiting insecticide

Twelve years later, I have not seen an EAB, but have seen the holes and the damage they cause.  When I bought my house, the first tree I installed was a Autumn purple ash, a cultivar developed at the University of Wisconsin from the white ash.  For six years now I have been having the tree professionally treated, and treated at least twice before that myself.  At a certain size the professional service is required.  The tree is treated every two years.  It is not cheap, and the total cost of treating will likely soon pass the cost of removal of the tree, but the tree holds value beyond the cost of removal.  The house and yard would not look the same with it removed, and it would take years for a new tree to reach its relative size.  I am not sure if at some point the ash borer leaves because no more trees are around for it to infect, not unlike herd immunity of viruses.

Insecticide being pumped to tree

Ash is a good strong wood that is used to make baseball bats, and is native to the United States. It is unfortunate that a bug can come from beyond the ocean and infect the tree, costing forests, streets and parks the canopy that can be enjoyed and bring along the other many benefits trees provide. They have created elm trees resistant to the Dutch elm disease, and researchers are working on a disease resistant ash tree.   However, like people, trees can have a different genetic makeup and it appears that the genetics of some green ash trees resist the EAB.  At Penn State they are thinking those trees may hold the key to survival.  Whatever the case, if we think Covid has a high mortality rate, the mortality rate of ash trees near the epicenter of its arrival in Michigan is over 99%.

Line from source dividing to multiple lines to the tree

To avoid the death of my tree, since EAB is in Dane County, and some say in McFarland, it is now treated every two years. This year it was treated on Friday, May 29.  The caliper of my tree requires eight holes pounded near the base of the tree about 1/2" through the bark to the cambium layer.  A chemical is injected by a hookup of small hoses and valves.  A regular bicycle pump provides the pressure for the injection.  The amount used, like the holes is based on the diameter of the tree.  In my case, about 25 to 30% of the bottle is used. It takes about a half hour for the injection process.

Close up view

It is not cheap, but the issue is that trees provide a variety of benefits, and I have chosen to have the tree treated.  Globalization has brought many good things, but we also need to examine the invasive species and the cost to determine appropriate cost/benefits. Yet, now it is too late.  I have always liked ash trees and it is sad to now see them disappear from their native habitat.  Perhaps pest resistant trees will reestablish the woodlands with ash trees.

Hole upon completion of treatment