Ever since 2002 the Emerald Ash Borer has been spreading vigorously. It has killed hundreds of millions of trees and costs property owners and forest industries millions of dollars. In 2015, ten new counties in Illinois were found to have Emerald Ash Borer beetles. They can wipe out all of the species of ash trees in the US if the problem is not acted upon. It’s no wonder that the Emerald Ash Borer beetles are considered the most harmful pest problem in North American forests.
The Emerald Ash Borer beetle (EAB) is assumed to have arrived in the US from its native country, Asia, by way of infested solid wood packing material on cargo ships or airplanes. It was first discovered in North America in 2002. In finding the destructive insect, the question to why so many ash trees were dying was answered. It only eats ash trees, including healthy ones. It was not found in Illinois until 2006 and it continues to spread to new counties and states.
The adult insects live 3-6 weeks and do little damage to the tree by eating the foliage. EAB larvae are the real threat to ash trees. Eggs are laid on the surface of the tree’s bark. Once hatched, the larvae eat through the bark and into the inner bark where transportation of nutrients is disturbed. When the insect matures it makes a D shaped hole in which it exits the tree. From there it roams within its range of 3-5 miles and starts the cycle all over again. It usually takes a year for an EAB to complete its entire life cycle, but in cold areas it may take two years. Depending on the size of tree, 1-4 years is the usual time it takes for an untreated ash to die after being infected. Unfortunately, in the US Emerald Ash Borer beetles have no predators other than woodpeckers and us.
Quarantine has been a big help in preventing the spread of Emerald Ash Borer beetles. It includes rules against firewood and live ash trees crossing into non-quarantined areas. Insecticides can also be used to prevent EAB damage.
Once a tree has been infected the damage cannot be undone. However, there are many treatments that can keep the infestation at a minimum in hopes of saving the tree. The sooner the tree is treated the more chance it has of survival. A solution can be injected into the tree and the inner bark that is functioning will receive the treatment and kill the beetles it reaches. This kind of treatment is best used during the spring when the tree is most active, but it is effective most times of the year. Other treatments can be applied to the soil, but can only be used at certain times of year. These treatments are good for smaller trees and trees that have little damage. There are also insecticide sprays that can be used on the tree.
The Emerald Ash Borer beetle spends about 90% of its life inside the tree. It is good to know the signs of an infestation, because they are often hard to spot in their early stages. EAB infestation usually begins at the top of a tree, where more nutrients exist from photosynthesis. Canopy thinning, under developed leaves, and early leaf loss, are earlier signs. Constant woodpecker activity and sucker shoots growing along the tree or at the base are later, more severe signs. And finally, sections and branches of the tree start dying. At this point the tree may not be saved and has become unstable with the possibility of being dangerous by loss of large branches. Dead ash trees, and trees that are more than half dead, should be removed as soon as possible to prevent damage from falling branches and possibly even the whole tree coming down.
Adult Emerald Ash Borers are metallic green in color and are about 3/8in - 1/2in long and 1/8in wide. They are usually active starting in June or early July through summer. Some insects that may be mistaken for the EAB are the Bronze Birch Borer, Two-Lined Chestnut Borer, and the Six-Spotted Tiger beetle, though the differences are not hard to spot.
The EAB larvae are cream colored and have bell shaped segments. They can be over an inch long fully grown. As the larvae eat the inner bark they leave "S" shaped zigzags that can be viewed if the bark falls off or is taken off.
Though our ash trees are in serious danger, there are ways to stop this insect. You can do your part by buying locally sourced firewood near where you are going to burn it. Next time you take a hike look for evidence of the Emerald Ash Borer beetle- it shouldn’t be hard.
The photos below are all trees that were damaged by the emerald ash borer beetle in forests near my home.