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Garden Q&A: How to deal with carpenter bees and improve lawn health this season

Q: Carpenter bees keep setting-up camp in my wooden deck and split-rail fence. Are they going to make the wood unsafe, and how do I get rid of them? They always seem to be chasing something, which makes me nervous.

A: Carpenter bees are valuable native pollinators if you can tolerate their antics. Personally, I’m always entertained by the behavior of the males patrolling their territories and have watched them chase anything from passing butterflies to pieces of tossed mulch. They don’t tackle every interloper — essentially they only care about other carpenter bees, and males can’t sting anyway — but they do pursue and investigate any flying intruders. The males have a pale square in the center of their face, so it’s easy to see what direction they’re facing as they hover like a little helicopter.

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A lone nesting gallery (tunnel) in wood is not going to cause serious damage, though several successive generations of nest cavities might compromise a wooden board after long-term use. The simplest deterrent is to paint exposed wood or to cover boards with aluminum flashing. Prioritize your deck (or any other structural wood) over the fence, which should be fine if they transfer their affections there.

If you need to interrupt repeated colonization of wood, try to seal existing holes and paint any unfinished or weathered wood (or replace pieces which are full of galleries) in late summer. This timing falls between the emergence of the latest generation and the re-use of a gallery for overwintering shelter, so the tunnels should be vacant. Alternatively, prevent gallery excavation at the beginning of the nesting season, no later than April.

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More information and control options are available on our carpenter bees page.

Q: My lawn looks like it needs some TLC, but I want to make sure I’m taking the right approach to improving its health. Where can I learn more about this process?

A: A great first step is to test your soil if you haven’t done so in the past three years. Soil-testing labs analyze samples for nutrient content, organic matter content and pH. The results will direct any fertilization or liming efforts for later this year.

Lawn is the most resilient groundcover in tolerating regular foot traffic, but if you don’t need to use parts of the yard very often, or if you have conditions that don’t suit turf, we strongly recommend you convert these areas to alternative plantings. This can be done any time of the year, though most lawn improvement methods are employed in autumn since that is the easiest time to establish new grass or boost grass vigor.

You can learn about the best lawn care management practices, plus which native groundcovers would make good lawn alternatives, in our upcoming master gardener webinar on May 25. Although geared towards an audience of educators, this virtual session is free and available to the public and you can find registration information at go.umd.edu. It may help to familiarize yourself with our lawn care guidelines beforehand.

If you want help with interpreting soil test results, you can attach a digital copy of your lab report to a question submitted to Ask Extension.

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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