We’ve got lots of carpenter bees — visiting the Cleveland Sage in our front yard, and now laying eggs above. About a year ago I saw sawdust below an old parrot perch sitting outside and over the next few months got to witness an adult carpenter bee drilling into the wood prior to laying eggs. Then I even caught a newbie below one of the holes as it adjusted to making its way into the natural world. We have other old wood posts where they appear to have nested – and I was glad to offer them nesting sites on our property. They are also very active in pollinating our flowers.
However, you hear so many negative things about them so I asked a couple bee experts — Robbin Thorp, Professor Emeritus from UC-Davis and Professor Keith Delaplane from U. of Georgia — for their views.
The takeaway: While the eastern carpenter bees are more problematic, the western ones are not and have a role as pollinators.
First, for background, large carpenter bees (genus Xylocopa) are wood-nesting generalist pollinators who forage wide range of food plants over a long season of activity, and tolerate high temperatures. More info:
3 California Species: According to Dr. Thorpe, the smallest is Xylocopa tabaniformis opifex, sometimes called the Foothill Carpenter Bee; the two largest are X. varipincta, the Valley Carpenter Bee; and X. californica, the California Carpenter Bee (which it appears we have). See photos below or BugGuide.net page for more photos and info.
Not Pests: Thorp says that for the most part western carpenter bees are not “pests” but he acknowledges that each person has their own definition of what is a pest.
Where they nest: X. tabaniformis nests primarily in untreated redwood lumber used in fences, arbors, patio furniture. “They have become very common in residential areas, since we provide them with so many home sites. As long as the redwood is not a supporting timber, the bees should not be a problem,” says Thorp.
X. varipuncta nests in dead limbs of trees rather than human structures. “The male of the species is a buff golden color with green eyes. We refer to it as the “teddy bear” bee.”
X. californica occurs primarily in the mountain foothill areas of northern and southern CA. It has bluish metalic tints to its body color and nests primarily in pithy stalks of yucca, sotol, and agave.
For more info and photos: See articles below by the UC Davis Department of Entomology, Communications Specialist, Kathy Keatly Garvey:
“In truth I find them interesting and amusing, and our urban entomologists consider them more a nuisance…. Dr. Keith Delaplane, U of Georgia entomologist
Dr. Delaplane is familiar with the eastern carpenter bee – Xylocopa virginica – which is considered a pest because they bore conspicuous holes in carports and siding. They can alarm people with their aggressive territorial flight behavior but added, “In truth I find them interesting and amusing, and our urban entomologists consider them more a nuisance than a problem on par, say, with termites. In general their structural damage is comparatively minor. So, in my book a relatively minor pest human-wise,” he says.
While many varieties of carpenter bees are helpful pollinators, Delaplane said the eastern variety are notorious nectar thieves, piercing the flower laterally to suck out the nectar and bypassing pollination. “Here in Georgia the holes they make in blueberry flowers then incites honey bees to visit the holes, thus becoming secondary thieves. A student’s research (Nectar Robbing Carpenter Bees…) showed that this secondary robbery costs the plant the seed set but not necessarily fruit set (one would think the two go together, but not necessarily).”
Another research paper on pollination Large Carpenter Bees as Agriculture Pollinators
Eastern resources: http://www.ent.uga.edu/bees