The emerald ash borer (EAB) is a very pretty looking insect with its emerald green covering. The insect is about as long as a penny is wide in the adult stage. That is about all the positive things I have to say about it, I'm afraid. There has been enough press on the little insect in recent months that I'm confident most of you reading this know a little bit about the insect and the devastation that it means for our native ash trees.
Never in my professional career has there been such gloom and doom information about a pest right out of the starting gate. Since its discovery in this country only about ten years ago, the outlook has not been good. The devastation that it has caused in Michigan since that time only demonstrates what is in store for the other parts of our country.
Most disconcerting is the fact that we have no way of combating the pest. There are insecticides that are being used to try and prevent infestation of specimen trees. The biggest problem is that they are expensive, require continued applications regularly, and quite honestly could pose other environmental concerns if used extensively.
And sadly, this is another example of a non-native pest wrecking havoc with a native species. The most recent example is Dutch elm disease which in this area wiped out our large American elm trees in the 1960s and 70s. And before that, it was chestnut blight which virtually eliminated the American chestnut more than a century ago. The American chestnut was once one of the most common trees east of the Mississippi river. It appears that the nation's ash trees will be the next.
There was hope when EAB was first discovered in Iowa in 2010 that the spread of this new pest would be slow. Adult beetles can fly only a few miles in any given year and must then find another ash tree to repeat the breeding cycle. The rapid and widely dispersed jumps that showed up in 2013 indicated that people were moving ash wood products out of infested areas. The most likely culprit is transporting firewood.
Other infestations will be discovered as more people become aware of the problem and start looking for it. It takes several years for populations of EAB to build up to the point where trees begin showing symptoms and dying. This means that initial infection of ash trees where the pest has been identified probably took place at least a couple of years ago.
We know that ash is one of the most abundant tree species in the country and has been widely planted in cities and parks following the loss of American elm. The USDA Forest Service estimates that Iowa has 52 million rural ash trees and 3.1 million more in urban areas. The DNR is conducting inventories of urban trees in communities with less that 5000 people and has completed nearly 250 so far. Ash comprises of 16% to 17% of city trees on average, but is as high as 87% in some areas. On Grundy County Conservation Board managed areas we have both native ash and extensive plantings that I helped plant in the 1980s and 90s.
The tree nursery areas that we have established since 2010 contain mostly mixed oak species and maples. As ash are removed, these will be their replacements.
One glimmer of hope is that this winter's near record-breaking stretch of cold weather may kill off some of the larvae and slow the spread of EAB. We can always hope.