The box elder bug mystery in my backyard

Eastern and western box elder bugs (Boisea trivittata and B. rubrolineata) are, in general, harmless bugs that feed mostly on the developing seeds of box elders and other maples. They use their piercing and sucking mouthparts to feed on box elder seeds, and not to pester humans.

However, pester humans they do! In the fall, boxelder bugs congregate in numbers, sometimes very large numbers, seeking a warm and sheltered place to hang out for the winter. When they can, they enter homes.

A cluster of box elder bugs on a house. Courtesy University of Wisconsin - Madison.

I recently had a reminder of how irritating these bugs can be. I had noticed "boxelder bugs" beginning to congregate on the  west and south-facing sides of my wooden fencing. I was familiar with them after living in northern Utah. A pest, yes. A problem, no. Inside, you simply catch one and transport it back outside. If you notice numerous bugs crawling on the carpet or windows, you simply vacuum them up. I didn't have any inside, but there were plenty - hundreds - on the fence. I got the Shop-Vac and went to town. The bugs don't have claws than can hold on in a windstorm, and those that didn't react fast enough soon joined their brethren inside the filter bag.

I was putting my recyclables in the alley when a neighbor came up to me, both apologetic and slightly apoplectic. It seems she was frustrated about the box elder bug invasion in her yard. She had "arborists" come out at least twice and spray her deck and walls. Her peace of mind clearly was affected, with bugs invading her place of relaxation outside.

Both arborists, it seems, blamed the invasion on a 2 inch dbh "box elder" they could see in my back yard.

I encouraged her to get her money back.

First, although I don't call myself an arborist (a term I personally reserve for people certified through the International Society of Arboriculture), I have taken numerous college-level courses in forest science, and for 5 years I was a hardwood specialist with UC Berkeley.

My point is, I can identify trees. The tree in my back yard was a maple, probably a landscaping hybrid, looking a lot like a red maple. It was most definitely NOT a box elder, with its characteristic pinnately compound leaves. In addition, when we purchased our home, this tree was in great distress, with half the upper branches dead and a good section of the bark on the main trunk missing. I had taken it upon myself to nurture this tree back to health, with careful pruning and watering.

You can see the tree growing through the deck in this photo. Note the severe bark damage.

I mention the health of the tree because unhealthy trees don't usually put their limited resources into seed production. In fact, I can say with certainty that there were zero seeds produced by this tree over 2 years. And box elder bugs feed on seeds.

Fact one: Regardless of the opinion of the arborists, this is not a box elder tree.

Fact two: There are no seeds to nourish box elder bugs.

Fact three: There are numerous large, seed-bearing maples scattered on the park strip around the block (but not my house). Box elder bugs will use other maple species for food.

Fact four: The bugs weren't box elder bugs.

What...?

Yes, the bug the arborists identified as a box elder bug was actually a red-shouldered bug, also known as a golden raintree bug (Jadera haematoloma). It took me literally 30 seconds to note that I had misidentified this insect. Note the very distinctive red shoulders compared to the box elder bugs pictured above.. Now, I know I'm not an entomologist. But if I was an arborist charging people to identify and treat insect infestations, you can bet I would get my insect identifications correct. 

And did I mention that the usual host tree for the red-shouldered bug was... the golden raintree, like the one in my neighbor's backyard?

That's right.  Rather than my non-box elder tree maintaining this non-box elder bug that bothered my neighbor, it was my neighbor's golden raintree maintaining the red-shouldered bug infestation.

Now, I don't blame my neighbor one iota. She was at her wit's end, and just wanted to do something about the bugs crawling all over her outdoor restful place. She hired what she thought was a professional, and was either misguided or defrauded. Twice!  Caroline mentioned to her that I thought the tree hosting the bug population was in her own backyard, and she didn't take it well.  I understand. Why believe me? She paid for professional advice, didn't she?

So, Caroline and I discussed the matter. Since our tree was going to take a number of years to heal and branch out, and Caroline really didn't like the hole in the deck area anyway, we decided to cut the tree down.  Boo hoo. In two days, Caroline removed the tree, had new decking delivered, and installed it.

I posted a note in neighborhood City Park West Neighbors Facebook page about these bugs, and noted the two types.

I also came across a Colorado landscaper with a YouTube video noting this particular insect, so some businesses get it right!

Mesa Turf Masters gets the identification correct!

I'll find some time in the future to sit down with my neighbor and discuss all of this. As I said, Caroline was never a fan of this particular tree, and originally I had to beg her to leave it. I like pruning and nurturing trees. And I do hope my neighbor can get her money back.

Louis J Bradley, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons