Ben Franklin: What's the buzz?
Published 6:00 am, Saturday, June 2, 2018
Q: I recently saw a report about a problem with burrowing bees in Midland. I didn't know bees could live underground. One woman said this type of bee attacked her husband. Are they aggressive? Should we be worried? What should we do if we find them on our property.
A: I spoke to Bart Heil, City of Midland park supervisor, to find out what the fuss was all about. Heil said that the bees were so called "digger bees" and that the nests had been exterminated. So, what do we know about digger bees?
According to Howard Russell, Michigan State University Diagnostic Services, Department of Plants, Soil and Microbial Sciences, not all bees live in hives like honey bees do. In fact, 70 percent of the more than 20,000 species of bees nest underground. One native bee species common in Michigan is called the "digger bee" because of its habit of digging its nests in soils. Sweat bees, leafcutter bees and mason bees also nest underground. This bee is solitary, meaning that every individual female builds her own nest, but many females (hundreds and sometime thousands) build their nests next to each other, so it is also a gregarious nester. Solitary bees range in size from 0.5-0.75 inches, and may be a variety of colors such as blue, green, copper or metallic red.
Their nests are easy to identify above ground because of the conical piles of dirt with a large hole in the middle that serves as the entrance to the bee burrows. Ground nesting bees generally prefer nesting in areas with morning sun exposure and well-drained soils containing little organic matter. Tunnels are excavated in areas of bare ground or sparse vegetation. If you have these conditions in your yard, you may find these bees showing up every year where you live.
Digger bees begin to appear during the first warm days of spring, and are only active for a few weeks, so they are a temporary nuisance. During the day, the active females collect pollen and nectar to carry back to the nest. A single egg is laid upon the pollen ball in March, April or early May. The males are looking for females to mate with.
Don't confuse solitary bees with ground nesting yellowjackets (Vespidae). Each female solitary bee constructs her own individual nest tubes, each with its own opening. Ground nesting yellowjackets, on the other hand, are social insects and a colony of several hundred wasps typically uses a single hole to enter and exit the nest. Solitary bees are gentle, well-meaning pollinators. Yellowjackets are basically jerks that aggressively defend their nests and readily attack and sting en masse. And as most of us know, yellowjacket stings are quite painful.
Many of us have a visceral reaction to the mere sound of a buzzing bee. And I do not want to minimize in any way the acute allergic reaction which some susceptible folks can have to a bee sting.
But yelling, "Mama get the hammer, there's a bee on daddy's head." just isn't appropriate.
And you may feel the urge to kill digger bees off with insecticide, but you really shouldn't because they are important early-season pollinators of spring crops like apples, blueberries and cherries.
They are not aggressive; they rarely sting unless hassled (males never sting), and their venom is rather weak. Try to put up with the bees if you can. Outdoor activities, including lawn mowing, can often be continued with no problem. However, with very large aggregations, you may prefer to avoid the area for four to six weeks while the nesting is taking place.
These bees may be difficult to control and may return year to year. If you have ongoing, intolerable problems with them, please consider using the following cultural methods, rather than insecticides, to control them.
* Ground bees like dry soils. Water the soil when bees first become active. Apply one inch of water once a week if it does not rain.
* Ground bees nest in dry areas where the grass is thin. Find and correct the problems making the turf thin. This may involve soil sampling, irrigation, soil aeration or other practices.
* Find ways to thicken the turf in these areas to reduce ground bee problems. Know the needs of the turf grass and meet them!
* In areas that will not grow grass, mulch the area.
However, if you feel you absolutely and positively must use a pesticide, look during the day to see where the holes are located. After dark, dust these areas with carbaryl dust (sold under the brand name Sevin and other names). A dust insecticide should cling to the bee's body better than a spray. Remember, the bees are not generally harmful, and pesticides are toxic; hence the cure may be worse than the problem because carbaryl is highly toxic to ALL bee pollinators. Depending upon conditions, carbaryl has a half-life ranging from 4 to 72 days in soil. It breaks down faster in sandy or well aerated soils. Carbaryl has a half-life of about three days on plant leaves (U.S. EPA). Before use, read and follow all printed instructions and keep people and pets out of the area while it is being treated.
Ben Franklin is an Advanced Master Gardener. The Midland County Masters Gardeners will answer questions from readers. If you have a question, you can email it to firstname.lastname@example.org or send it to The Midland Daily News at 124 S. McDonald Street, Midland, MI 48640.