Emerald Ash Borer a Threat to All Ash Trees

Spread of Emerald Ash Borer puts area ash trees at risk

Bill Sevier: Ask a Master Gardener

Saturday, October 29, 2016

Q: My friends in Michigan say they are losing their ash trees to an insect. Is my tree at risk here in Tulsa? Jim, Tulsa.

A: Your ash tree is not at risk yet but may very well be in the near future due to an insect called the Emerald Ash Borer.

This insect, like so many of the insects and diseases that have devastated trees in the U.S., is an import from Asia. This has the same potential for destruction of all varieties of our ash trees, as did the imported diseases that killed our elms and American chestnuts.

The Emerald Ash Borer was first seen near Detroit in 2002 and has been noted to spread initially eastward then onto states south and west. Until recently, it had been found in all surrounding states but not in Oklahoma. Recently, it has been reported in the northeastern part of the state and can only be expected to spread. The borer often is transported to new areas by firewood and nursery stock.

The insect is said to cause the death of many millions of ashes in the heavily involved states, and that potential exists for all our ash trees.

The borer adults are metallic green and about ½-inch long. The adults do little damage, but their larva bore into the outer layer of ash trees, where they feed and slowly block the circulation of the tree. Trees initially experience dieback of the uppermost part of the canopy, which spreads to involve the whole tree. Trees often have stress-induced secondary shoot growth on trunks and at the tree’s base.

Studies looking at ways to prevent infestation and to treat those trees already involved have shown there are effective controls, but they are most effective when used for prevention. Trees with borers may benefit from treatment at early stages of involvement, but most likely those trees with dead tops will die over the next few years.

The effective insecticides are all “systemic,” which means they must enter the tree’s circulation. This is done as a soil drench over the root zones; by injection directly into the tree, or spraying directly on the tree’s trunk. Injections must be done by an arborist, but drench and trunk spraying can be done by homeowners.

The big question involves which trees to protect and when to do it. Treatments are expensive, time consuming and add insecticides to the environment. This should only be done with forethought.

Currently, trees should be considered for treatment if the borer has been found in other trees within 10-15 miles. That is not the case as yet in Tulsa but likely will be in the future.

More information about the Emerald Ash Borer and preventative measures may be found on the website of The Emerald Ash Borer Information Network at emeraldashborer.info. Also look at the Oklahoma Forestry website for description of signs of the insect’s tree involvement.

Be aware that the OSU Extension Offices in Oklahoma will keep track of the spread of the beetle and publish information as to the locations.

Garden tips

§  Keep leaves off of newly seeded fescue to prevent damage to the sprouts. Also, the soil of newly seeded fescue should be kept moist until the sprouts are about 2 inches, then water less often and for longer times to encourage deep root growth of the seedlings.

§  Remove vegetable garden debris to prevent many garden pests and diseases from overwintering in these materials.

§  Plant cool-season cover crops like Austrian winter peas, wheat, clover and rye in otherwise fallow garden plots.

§  Cover water gardens with netting to keep out falling leaves.