Insect borers provide lessons in Community Education Garden

By Mary Fran McClure
WSU Chelan/Douglas County Master Gardener
June 22, 2022

Insect borer damage to tree trunk.
Look for sawdust and holes similar to this photo if you have a shrub showing dieback problems. When cutting the wood, you might find some fat larva. Take the wood and any larva to a Master Gardener diagnostic clinic for guidance. – Provided photo/Mary Fran McClure

Mary Fran McClure
Mary Fran McClure – WSU Extension Chelan/Douglas County Master Gardener – photo by Don Seabrook, Wenatchee World

The Community Education Garden is educational both for WSU Chelan/Douglas Master Gardeners, as well as the community.

The lovely garden at the northwest corner of Springwater and Western avenues is open for you to stroll through most any time, just don’t pick flowers or vegetables. It’s a great place for ideas and learning, as well as the just plain leisurely pleasures of a walk around an interesting landscape.

Our recent learning experience involves several vigorously growing elderberry bushes that were a major part of screening the garden from the adjoining gravel parking lot.

In the fall of 2020, Tawnee Melton, coordinator of the Welcome Garden portion of the large garden, started noticing some dieback on one of the elderberries and found sawdust, a sure evidence of a boring beetle infestation.

Fortunately, Melton is part of our diagnostics team, as well as a research associate at the WSU Tree Fruit Research and Extension Center, where our garden is located. Her expertise and experience are immensely helpful in diagnosing problems we encounter.

“When we cut back the affected limbs, we found holes bored down the canes towards the base and even found several live beetle grubs,” she explained. “There were a handful of potential boring beetles that could have been the culprit and beetle larvae are very difficult to ID.”

Limbs showing dieback were pruned back during 2021 and there was discussion on whether to remove the shrubs completely or try a different approach. Because elderberries are so resilient and fast growing, Melton said they decided to have the bushes cut down to the ground and then applied a systemic insecticide to the roots. The hope was to eliminate the beetles and larvae while allowing the shrubs with healthy root systems to recover.

This spring the bushes are growing well with lush, new foliage. Hooray!

“As for the insecticide,” Melton says, “I would not normally choose this systemic method because this also means that the flowers could be toxic to bees this summer, and to counter this effect, I will be keeping all flower buds pruned off this year.”

This is an important reminder to gardeners who think the systemic pesticide route is a win-win alternative — your roses or other flowers might look healthy and flourish while you are unintentionally hurting our important pollinator population of bees and other helpful insects.

Melton is optimistic about the treatment working, as she found one dying adult beetle beneath one of the bushes in late May. This provided her with a specimen to identify the borer — Desmocerus auripennis or Golden winged elder borer.

“Hopefully this concludes the saga with the elderberries. Mystery solved,” Melton said.

This experience shows that we Master Gardeners also have our challenges in gardening, and the education garden is a learning experience for us as well as you, our visitors.

If you have a plant or insect problem, a great way to find some answers is checking with our diagnostic clinic. Master Gardeners provide a weekly in-person clinic right at the Community Education Garden on Thursdays, between 4 and 6 p.m., through September. Another alternative is visiting our Third Saturdays in the Garden where we have a clinic diagnostics table. The next event is Saturday, July 16 from 10 a.m. to noon in the same garden. Yet another alternative is to email your questions to

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