A Pain in our Ash

Justin Kitzrow
2/28/11
A Pain in our Ash
We are under attack from an invasive metallic green insect that is infesting our native ash trees of Wisconsin. This invasive insect is the Emerald Ash Borer (Agrilus planipennis) which is a native insect of Asia. How is it that this insect made its way over from Asia you may be asking yourself? Among professionals in the forestry community it is believed the beetle was transported to the U.S. in packaging and shipping materials such as crates, wooden boxes, and pallets. Ground zero for this invasion is Detroit, Michigan. The beetle was first discovered in ash trees in the Detroit area in 2002. Foresters believe the beetle may have gone undetected for as many as 8 years. Since 2002 the beetle has been on the move spreading to other states in the mid-west.
This insect as an adult is capable of flying roughly half a mile. How is it then that this insect has made its way throughout the Mid-West? The beetle has become a big problem in the wood products industry as the beetle can be living in the logs or pieces of firewood which are transported down the freeway. Spread from state to state in shipping materials has become a large problem in addition to transportation by car.
Now this invasive insect is in our home state of Wisconsin. Emerald Ash Borer has been in our state since 2008. Our native ash forests are in danger of being wiped-out by this insect. Once a tree is infested by this insect it is fatal for the tree. In cities around the state ash trees have become a very popular street tree. Ash trees are resistant to most diseases which is a reason they have become such a popular street tree. In my work with the city of Wausau during the summer of 2009, I did an inventory of ash trees which will be used in the future for prevention planning purposes.
The insect itself has different stages to its life cycle. Scientists believe that it only takes about one year before an adult female is capable of producing eggs. The life of this insect begins at this stage were the egg is laid on the tree. Once the egg hatches a small flattened larva feeds on xylem tissue just inside the bark which ultimately kills the tree. The larva is creamy in color and ranges in size from a quarter of an inch to one and a half inches in length. Larval stages of this insect cause the damage which kills most trees. The larva will feed on the wood inside the bark until they reach the adult stage which is when they will emerge from the bark of trees. The adult stage of Emerald Ash Borer is a metallic green color and ranges in size from an eighth of an inch to a quarter of an inch.
As stakeholders in our urban and rural forests you as citizens need to be on alert for signs of this insect which has become a pain in our ash. There are different signs you can look for that may alert you to Emerald Ash Borer’s presence. The first and most obvious sign is the insect itself. Simply observing the adult or larva in a tree would be a key sign of a problem. Also along with the insect you will see signs that it has been attacking a tree but you have not seen the insect. Watch for D-shaped exit holes on the bark of the tree; this is a sign that the adults have emerged from the tree. You may also watch for S-shaped feeding patterns below the bark which are signs of the larva stage. In the canopy of the tree you may begin to see dieback of the canopy which occurs due to the lack of nutrients reaching the tree to produce and sustain growth. Finally, there are two signs you may watch for near the ground which could indicate Emerald Ash Borer. First you may begin to notice peeling bark from the trunk of the tree. This is a sign which occurs from the larva feeding stage. There also may be sprouts which are growing from the trunk of the tree which the tree does to combat a wounding. An example of wounding would be the larva feeding on the xylem tissue of the tree.
There is no way to prevent the beetle from killing a tree once it has become infested. Therefore, we as stakeholders need to become more aware of this invasive insect and educate each other on the signs of this insect. By working together and not moving ash products we can greatly reduce the spread of this insect. It is our forests we are fighting for. If we work together to educate others and the community, this would be a great first step in reducing the spread of this pain in our ash.