Q&A: Do Beetles in Old Wood Harm Trees?

a black beetle on a log - bess beetle
Patent-leather beetle on a rotting log. Photo: M. Talabac

Q:  I found several of these beetles in an old decaying stump and am concerned for my healthy trees. Will they attack live trees?

A:  No, these beetles feed on rotting wood and the fungi decaying it, and they pose no threat to other trees. Several common names are given to them: Patent-leather Beetle, Bess Bug, and Horned Passalus.

These insects have a rare life history in that they live in groups and provide parental care for their larvae, feeding them pre-chewed rotting wood, likely for over a year while the young mature slowly.

The feature I find the most entertaining about them is their ability to squeak. Both adults and larvae can stridulate, which means they use one body part to rasp against another to create noise. The purpose of this is probably to communicate with each other. Cricket chirping and katydid calling are forms of stridulation, but in the case of these beetles, it produces more of a high-pitched sound akin to a person making “kissy” noises at a pet.

Interestingly, Iowa State University’s BugGuide web page for Bess Beetles speculates that the “bess” part of its name might derive from baiser, French for “to kiss.” (Or it’s derived from the fact that their forward-facing jaws can pinch, though I’ve never been bothered and I pick up these beetles every time I see them because they’re fun to find. “Petting” them sometimes makes them stridulate, which is always endearing.)

Wood-recycling insects like these are great to have around and rarely if ever pose a risk to healthy plants. Not only do they get those old stumps and logs out of the way for free (even though it can take a while), but both they and the fungi they work with are a means to make the old tree’s nutrients available again to the rest of the ecosystem.

By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun and Washington Gardener Magazine. Read more by Miri.

Have a plant or insect question? The University of Maryland Extension has answers! Send your questions and photos to Ask ExtensionOur horticulturists are available to answer your questions online, year-round.

Q&A: Why do my cucumber and zucchini plants wilt?

One Spotted and multiple Striped Cucumber Beetles, feeding on overripe pumpkin. Photo: Whitney Cranshaw, Colorado State University, Bugwood.org

Q: Last summer I had cucumbers and zucchini wilting and dying even though I’m pretty certain I didn’t have root rot or squash vine borer. What should I try this year so I can hopefully get a harvest?

A: Bacterial wilt disease, transmitted by cucumber beetles is the prime suspect for crop failure in this instance. Both of these garden pests – Striped Cucumber Beetle and Spotted Cucumber Beetle – are native to North America and can cause serious damage to vegetables in the squash/cucumber family, though they can also feed on unrelated fruits, vegetables, and ornamental plants.

Although their feeding causes direct plant damage, the main issue comes from their introduction of one or more plant pathogens. These beetles can transmit diseases like bacterial wilt and viruses, none of which are curable.

Delaying the planting of squash and cucumber transplants until mid-June may evade the host-seeking adults. Until they bloom, cover plants with insect netting or row cover (the former is ideal as it doesn’t trap heat). Bees will need to reach the flowers for pollination, but once the fruits start to develop, plants tend to be less susceptible to infection. Since more than one beetle generation can occur per year, clean-up veggie garden debris in autumn to deny remaining adults overwintering shelter.

For now, ‘County Fair’ is the only available variety resistant to bacterial wilt. This pickling cucumber is parthenocarpic– it produces mostly female flowers that don’t require pollination to set fruit. The Cucumber Beetles page at the Home & Garden Information Center has more information about these insects and their management.

By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun. Read more by Miri.

Send home gardening questions to Ask Extension at the Home & Garden Information Center

No-till gardening and weed barriers

In a mid-March post, I wrote about the advantages of using heavy-duty weed barrier fabric to smother weeds and create a no-till plant bed. In mid-June, I found myself with two beds that were starting to get weedy. The winter cover crop that had protected the soil was quickly decomposing and crabgrass and broadleaf weeds were emerging.

Rapidly growing weeds are quickly brought under control with weed barrier fabric.

I threw on 3-ft. wide strips of the weed barrier material and after five days of very hot weather all of the vegetation was dead. Continue reading