Forester educates city about ash borer
About 70 people in town attended presentations Thursday about the emerald ash borer and what it will do to Fairfield’s ash trees.
The Fairfield Arbor Committee invited forester Tivon Feeley of the Department of Natural Resources to speak about the menacing insect at three meetings at the Fairfield Public Library.
Feeley said the emerald ash borer leaves telltale signs of its presence both on the inside and outside of a tree. When the borers exit a tree, they leave an exit hole in the shape of a capital letter “D.” Another method to identify EAB in a tree is the way woodpeckers attack the tree.
Since the ash borer is not native to this area, the woodpeckers here don’t know what it is when they find it. Feeley said they’re not sure if they want to eat it, so they peck all around the holes in the bark, which creates bare patches on the tree.
When foresters or arborists have a chance to look beneath the bark they can identify the EAB by the way the larvae eat the wood. Feeley said he doesn’t know why but the EAB larvae eat through the tree in a zigzagging, serpentine pattern. The larvae cut the veins that allow the tree to transport nutrients from the roots to the canopy. A sign that a tree is infected is its center branch will begin looking sparse.
Feeley said the EAB has become especially bad in the Midwest recently because of consecutive years of drought. The drought puts stress on the trees, and those are an inviting target for the EAB, which prefer distressed tress.
EAB infected trees have been found in five counties in Iowa. Feeley has made some alarming discoveries in two of those counties in southern Iowa, Jefferson County and Des Moines County. He has found EAB larvae in infected trees at unusual times of the year when the larvae should have turned into adults. Feeley fears the EAB may be having two generations in a single year in southern Iowa, which means it could spread twice as fast. However, Feeley said his hypothesis has not been confirmed by other scientists, and he’s still collecting data to prove it.
Another theory Feeley would like to test is how the EAB have been able to move so quickly between towns. He is especially perplexed at how the EAB could end up in Union County in southwest Iowa when all of the other reported cases have been confined to counties far away on the eastern edge of the state. He noticed the Burlington Northern Santa Fe Railroad goes through Burlington and Creston, in Union County. He said it’s possible an ash borer got on a train in Burlington and got off in Creston.
As to how the EAB found its way to Fairfield, Feeley said it’s likely the EAB arrived on infected firewood. He said that is the most likely scenario, especially considering he and other foresters have looked for EAB in Henry County and have not found it.
Feeley discussed a few treatment options available to people with infected ash trees. One method he does not recommend is drenching the soil around the tree with insecticide. He said pouring insecticide around the tree can end up in groundwater. Additionally, gardens near the tree cannot be harvested since they, too, would be poisoned with the insecticide.
Fairfield city councilor Michael Halley was in attendance at one of the meetings and told the audience the council is considering a ban on drench insecticides anyway, so it may not be a legal option to Fairfield residents in the future.
Feeley said injectable insecticides are much better for the environment because they are confined to the tree. However, he said they have to be injected every year for the life of the tree.
A member of the audience asked Feeley if healthy ash trees should be cut down even before they are infected with EAB or if they should be taken down only after infection. Feeley said the trees could be taken down after infestation, but it would cost more since the trees would be brittle from the infection and thus more of a danger to the person bringing them down.
Feeley said the EAB is a threatening bug, but the insect that keeps him up at night is the Asian longhorned beetle. The beetle kills several species of trees such as maple, birch, elm, ash and buckeye. It’s a large insect, the size of a human thumb, and when it exits a tree it leaves a hole the size of a dime. Feeley said it kills trees with lightning speed, often within a year after infection.
One thing Feeley is pleased to see is how the state has responded to these perils. Iowa was the first state to proactively exam its trees for signs of the Asian longhorned beetle even before there were signs of infected trees. He mentioned one town that has sought to control a pest problem by giving homeowners a different species of tree from their neighbors, to prevent future pests from spreading rapidly.