by Cynthia Kerson

I've been attacked by boxelder bugs (Boisea or Leptocoris [depending on the website] trivittata). There are thousands of them throughout my property. In researching how and why they are suddenly in my world (or maybe I am suddenly noticing them?), I found the following:

They love Manitoba maple trees, also called California boxelder (Acer negundo) locally, hence the name of the bug. Not knowing, I searched what a boxelder tree looks like. UCIPM didn't have a Pest Note or a description of the bugs or the trees, so I explored an outside the website. The trees have small red (male) or yellowish (female) flowers that blossom March-May and remind me of the polliwogs that I grew up with on the East Coast. Their serrated leaves can be white and green or all green. Their multiple trunks are smooth and greyish in color, and they happily mature to about 25'-50' in acidic, low nutritive soils. For this reason, they're common in cityscapes. Having been unaware of the tree, I explored my property and found a couple. Most of what I read advised that the tree borders on ugly as it ages since the flowers are not attractive and droop to look like “dirty socks.” I agree and am not impressed. The ones on my property are outside the fence where “the wild things are.”

While I was exploring my property looking for the trees, I noticed some ripe figs on my mission fig tree. I picked them, imagining broiled figs with dinner tonight. Lo and behold the little buggers were swarming the ripe fruit. So, while I didn't read this anywhere, it's apparent they like figs. I also read that they are attracted not only to the boxelder maple, but to the seeds of most maples and ash trees. This made sense since I only found two boxelders which are outnumbered here by other types of maple trees. They also like warm spots. Imagine my annoyance when I opened the cover of my hot tub one morning. They will cluster on warm building sides, facing the sun. Their frass (poop) will discolor a light-colored surface.

The boxelder bugs are about ½” long and red with black markings on their hard backs. They are true bugs with the tell tale "X" on backs of adults insects where their wings fold. When you squish them, they bleed—gross. I am swatting them with a fly swatter whenever I can because I read that they are quite prolific. They will come into the home—good grief! I learned that spraying them with either water and dish soap or a mixture of vinegar, water, and dish soap (I use 45% vinegar), which I keep on hand to spray clover weeds, is a good solution to get rid of them. When I spray the mixture, they drop off right away. I've noticed fewer and fewer of them over the past week, which may be due to my determined effort, the rain and cooler nights, or both. (As an aside: I spray clover, rather than pick it, because if you rustle the plant, it will drop seeds – you can hear them drop if you are close enough). Another remedy for the boxelder bug is to vacuum them, which I have also been doing. Once I have a bunch sucked up, I smother them by wrapping plastic wrap with elastic band on the end of the vacuum hose to be sure they don't climb out and into my garage. At least, I assume they're being smothered. Who knows, I could open the canister and find a boxelder dance party going on! I would check for the sake of this post, but I'm too nervous the latter would be true.

Napa Master Gardeners are available to answer garden questions by email: mastergardeners@countyofnapa.org. or phone at 707-253-4143.  Volunteers will get back to you after they research answers to your questions.

Visit our website: napamg.ucanr.edu to find answers to all of your horticultural questions.

Photo credits: Cynthia Kerson

Information links:

UC ANR http://ipm.ucanr.edu/PMG/PESTNOTES/pn74114.html

UC IPM http://ipm.ucanr.edu/PMG/GARDEN/PLANTS/boxelder.html