Experts tackle readers’ garden questions.
Q: Recently, we saw this damage on our tree. Can you help or tell us where to go for help?
Petra Tavano, West Sacramento
Horticulturist Ellen Zagory: After enlarging the photo and looking at leaves and buds on the stems, my guess is that it is a Moraine ash tree (Fraxinus holotricha “Moraine”). It does look like other photos online for that (variety).
Ash is susceptible to ash borer (Podosesia syringae), which would make the oozy-looking wounds, although it could be accompanied by drought, construction or other kinds of stress to make it worse.
If it is a valuable old tree, it might be worth getting an arboricultural consultant or arborist to take a look and get a positive identification. Or see if a local master gardener or county agent can take a look. (For suggestions, contact the Yolo County master gardeners at the phone number listed under “Garden questions.”)
More detailed photos and careful attention to photo focus – particularly up close – are always important in making a positive diagnosis.
Editor’s note: Moraine ash was a relatively common landscape tree in the Sacramento area before the ash borer insect showed up. A serious pest in other parts of the United States, the ash borer first appeared in Sacramento in May 1979, according to the UC Cooperative Extension. It has since taken a toll on local populations of this handsome deciduous tree.
A clear-wing moth, the adult ash borer looks a lot like a wasp or yellowjacket. Its black body has narrow yellow bands. It attacks ash, olive, lilac and privet. Most of its damage is done to trunk and branches 5 to 10 feet from the ground, according to the University of California pest notes. Infestations often occur where bark has been damaged due to pruning, improper staking or previous borer damage.
The adult ash borer lives for just a week. The females lay eggs in gnarly or rough bark. After the eggs hatch, the larvae tunnel down into the wood, feeding and causing great damage. Eventually, the larvae pupate underneath the bark; in spring, they appear as the adult moth.
This pest often attacks trees or shrubs that are already weakened or stressed by drought or compacted soil. To help it survive, make sure the tree is well irrigated and that its roots have good aeration.
Ellen Zagory is the public horticulture director at the UC Davis Arboretum.
Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties. Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to firstname.lastname@example.org. Please put “Garden Detective” in the subject field and include your postal address. To contact UC Extension directly, call:
- Sacramento: 916-875-6913; 9 a.m.-noon and 1-4 p.m. Monday-Thursday
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- Colusa: 530-458-0570; 9 a.m.-noon and 1-4 p.m. Tuesdays; website: cecolusa.ucanr.edu
- El Dorado: 530-621-5512; 9 a.m.-noon Tuesday-Friday
- Placer: 530-889-7388; 9 a.m.-noon Tuesday-Thursday or leave a message and calls will be returned; website: pcmg.ucanr.org/got_questions
- Nevada: 530-273-0919; 9 a.m.-noon Tuesday-Thursday or leave a message
- Shasta, Tehama, Trinity: 530-242-2219; email email@example.com
- Solano: 707-784-1322; leave a message and calls will be returned
- Sutter, Yuba: 530-822-7515; 9 a.m.-noon Monday-Tuesday and 1-4 p.m. Thursdays
- Yolo: 530-666-8737; 9-11 a.m. Tuesdays and Fridays, or leave a message and calls will be returned