KC Gardens

The emerald ash borer continues to take its toll on Kansas City-area trees

Ash trees were once a popular thing to plant and can be found lining the streets and filling backyards throughout Kansas City. Unfortunately, they are no longer available in nurseries because of the detection of emerald ash borer in 2012 in the metro.

Considered native in China, this beetle was accidentally imported to the United States. Trees in China and the beetle learned to coexist and survive. But in the United States, the green and white ash species have not evolved, resulting in thousands of dying trees. Green ash, those with yellow fall color, are infected first, while white ash, with purple fall color, may not yet be showing signs of damage.

The infestation slowly spreads as the wood-boring insects multiply. Depending on your neighborhood, infected green ash trees are either in severe dieback or already dead.

An early symptom is a thinning upper tree canopy. Then water sprouts, or sucker growth, develop in the middle of the tree just above the main trunk. You can see a declining crown and a bright green middle. As the insect feeds more, the top dies completely, and shoots develop along the main trunk. The tree finally dies slowly over three years or more.

Once the upper limbs are damaged, they become unstable and likely to break, potentially harming pedestrians and parked cars nearby. It doesn’t take a storm for the branches to fail. I have seen limbs fall on a calm day. My advice is do not park under a declining ash tree.

There is only one course of action when a tree is infected: removal, as it has become a liability. Some cities have programs to assist residents with the removal of dying trees. Check with your city’s neighborhood services or parks department.

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Because of the emerald ash borer, infected trees are either in severe dieback or already dead. Johnson County K-State Research & Extension

I decided to remove our ash tree before it progressed to the point of crown death. The literal (and figurative) breaking point was the limb falling out of the tree onto the driveway. The tree was easy to remove because it was along the street. Removal is only part of the expense. Planting a new tree in its place adds to the total cost of the infestation’s effect.

There are insecticide treatments available to help stop the emerald ash borer. Unfortunately, for most trees in our area it is too late to start, especially in green ash. Some white ash trees that are not yet showing symptoms could be treated.

Green ash is currently under attack in the metro from a secondary leaf disease, mycosphaerella leaf spot. Unlike the emerald ash borer, this causes the leaves to drop throughout the tree, and no sucker growth is evident. This leaf disease is a result of the wet summer, and the tree will recover — until it is infected with the emerald ash borer.

Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Got a question for him or other university extension experts? Email them to garden.help@jocogov.org.

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