Home & Garden: Is the emerald ash borer in western Colorado? | PostIndependent.com

Home & Garden: Is the emerald ash borer in western Colorado?

Curt Swift
Free Press Gardening Columnist
Emerald Ash borer
Submitted photo |

As far as I know, we don’t yet have emerald ash borer in western Colorado. It has been identified in Boulder and Erie; and as long as wood cutters, hunters, and others don’t haul ash fire wood over the mountains, we won’t have this insect killing trees in our communities for many years. Emerald ash borer is responsible for millions of dead trees in the Midwest. When it arrives in western Colorado, it will cause irreparable damage to our urban forests. The Colorado State Forest Service is recommending ash trees no longer be planted and other trees be used to reduce the monoculture of ash we currently have in our communities. Many of us remember the days of Dutch elm disease. This disease was extremely devastating due to the number of elms planted in our communities. Many communities were totally stripped of trees by this disease as elms were the only trees in those communities.

A lot of homeowners have planted ash trees around their homes. Interplanting other types of trees with your ash is recommended. When (not if) the emerald ash borer arrives in western Colorado, you will stand a better chance of having live trees still standing after the ash borer takes out your ash trees. There are pesticides you can use to protect your trees and help cure them if they are attacked by this beautiful insect. Those treatments, however, will cost money and many will most likely not be able to afford treating their trees.

At present, treatments are supposedly not necessary. This insect lays its eggs on the bark. When the eggs hatch, the larva bore through the bark and feed inside the tree. The adults emerge from trees by eating their way through the bark, leaving a D-shaped hole about 1/8-inch across. Many other insects also bore into ash and other trees, most of which create exit holes from which the adults emerge that are larger than 1/8-inch across. Many of those holes are round, not D-shaped. If you see holes of the proper size and shape for the emerald ash borer, I would suggest you get in contact with Tom Ziola with the City of Grand Junction Parks Department. Be sure to use a ruler to confirm the size of the hole before you call Tom. The easiest way to confirm the presence of this insect is to capture an adult, otherwise the bark needs to be peeled from an infested branch, the larvae teased out and preserved in alcohol and sent off for identification.

David Gordon with the Colorado Department of Agriculture will be putting out traps in Mesa, Delta, and Montrose counties to help determine if this insect is already here. These sticky traps will have an attractant in them which entices the beetle to the sticky material in the trap.

The CDA and your local city departments of forestry and arborists could use your help in determining if this insect is here. Check your ash trees and if you notice suspicious holes, let us know. Use a ruler to confirm the size of the holes. Remember, holes larger than 1/8-inch are too big for this borer. If you have holes of other sizes in your trees, you most likely have some other boring creature and it is best to have it checked out before your trees are so badly damaged they are unable to recover.

Many boring insects invade trees stressed from root damage, lawn mower scars, and other factors. As I drive around the area I see many homeowners tilling up their yards in preparation of seeding or laying sod for a new lawn. Some of these individuals are rototilling around ash and other trees, damaging tree roots in the process. Damage to roots is a stress many trees can’t tolerate. Root damage means die-back of branches. Many species of trees don’t show this damage for several years after you have tilled up the soil around the tree. Other trees show such damage within a year. Even if you can’t see any change in the tree due to root injury, the insects that feed on stressed and damaged trees can sense this change in health and are attracted to these trees.

If you have a lawn that is in need of renovation and you have trees and shrubs in or next to that lawn, it would be prudent to look into having the lawn aerated and seeded in lieu of tilling it up. Several lawn care companies have aerators and can seed the lawn for you.

High Country Lawn even has seed available for sale at their office at 2426 H Road in Grand Junction if you want to aerate and seed the lawn yourself. Otherwise check with them to see when they can seed your lawn to increase its vigor and health without damaging the trees you have in your lawn.

You can scatter the seed, aerate the lawn, scatter a topdressing of Ultra Fine compost or 1/8-inch screened Mesa Magic (both available from the Mesa County Compost Facility on Orchard Mesa) and rake the area to move the seed and compost into the aeration holes. Keep the top 1/4-inch of soil moist to ensure germination and establishment of the new lawn.

GJ Free Press columnist Dr. Curtis E. Swift is a retired horticulture agent with the Colorado State University Extension. Reach him at Curtis.Swift@alumni.colostate.edu, 970-778-7866 or check out his blog at http://SwiftsGardeningBlog.blogspot.com. He owns Swift Horticultural Consulting and High Altitude Lavender.

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