Garden Detective

How to solve an insect mystery

Garden Detective: What’s this bug? Lindley Karstens found it inside a dying fruit tree in Modesto.
Garden Detective: What’s this bug? Lindley Karstens found it inside a dying fruit tree in Modesto.

Experts tackle readers’ garden questions.

Q: We recently moved into a home in Modesto that had 15 assorted trees on the large back yard, several of them plums with signs of advanced decay. When cutting through the lower portion of the worst of the dying trees (heartwood completely eaten out), I encountered a large number of black beetles about 1 inch in length.

Although we are working to remove all the dying trees, I am concerned for the citrus and cherry that seem to be healthy. In addition to removing the plum trees, what can I do to discourage them from attacking the oranges, kumquat, tangelo, grapefruit, and recently planted lime, fig, and lemon?

Lindley Karstens, Modesto

Bee garden writer Debbie Arrington: Our insect experts could not identify the beetle from your photo. But if you still have this mystery insect in a jar, that’s good. That’s your pest sample.

“Unless I see the beetle, I would hate to guess as to what the beetles are and if they are of concern,” said retired state entomologist Baldo Villegas, Sacramento’s “Bug Man.” “I can’t think of any pest beetles of that size that would be active at this time of the year. I doubt if any of those beetles would be a threat to the other trees in the yard.”

The first thing to do is get a positive identification of that beetle. For starters, it might not be a beetle.

“I highly recommend that she takes the sample to her county agricultural department or UC Extension Service for an ID on the insect to see if it is indeed a beetle or something else that looks like a beetle,” Villegas said. “Correct identification is of utmost importance when making a recommendation.”

In Modesto, contact the Stanislaus County UC Cooperative Extension office at 3800 Cornucopia Way, Suite A, Modesto, CA 95358. Phone (209) 525-6800 in advance for office hours or to make an appointment.

The Bee’s Debbie Arrington is a consulting rosarian and lifelong gardener;, 916-321-1075, @debarrington.

Garden questions?

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 h& Please put “Garden Detective” in the subject field and include your postal address. To contact UC Extension directly, call:

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