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Garden Q&A: How to avoid cucumber beetles and protect fireflies this summer

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.

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Although their feeding causes direct plant damage, the main issue comes from their introduction of one or more plant viruses. 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 floating 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, cleanup veggie garden debris in autumn to deny remaining adults overwintering shelter.

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For now, County Fair is the only available variety resistant to bacterial wilt. This pickling cucumber produces mostly female flowers that don’t require pollination to set fruit. Our Cucumber Beetles page has more information about these insects and their management.

Q: I’ve started to see this year’s fireflies flashing, and they always bring me joy! Can I do anything to help protect them?

A: As with many wild creatures, fireflies are dependent on appropriate habitat and can be supported by gardening efforts that minimize habitat degradation and disturbance. Eggs are laid in sites with damp soil, and larvae hunt in moist environments where prey like slugs and snails thrive. If you have soil drainage issues, see if your yard is suitable for a rain garden, since firefly larvae thrive in damp areas. These juveniles run around for nearly two years consuming mollusks and other insects, so undisturbed ground covered in low-growing plants and/ or intact leaf litter offers them shelter and favored hunting grounds.

The fascinating and much-loved trait of these special beetles — light flashing — benefits from relatively dark conditions with minimal light pollution so adults can find each other using this back-and-forth communication. You may not have much say in the use or brightness of street lighting, but you can keep your external home or landscape lights off, which will also spare migrating birds and plenty of other night-flying insects from wasting energy becoming disoriented, distracted, or more exposed to predators.

Reducing or eliminating pesticide use spares both the fireflies and their prey, and where possible, retaining some plant debris (dead logs, brush piles) gives them additional places to hunt and hide.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Extension” to send questions and photos.


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