Controlling Varroa Mites

The Varroa mite remains the most deadly parasite of honey bees, and the control of Varroa is the most important issue in honey bee colony health. Tracheal mites pose a decreasing threat, but the Varroa mite continues to kill honey bee colonies. Varroa mites develop inside the capped brood cell with the developing honey bee pupa. During the honey bee’s development and after it emerges as an adult, the Varroa mite sucks nutrients from the bee. To access the bee’s blood, or hemolymph, the Varroa mite penetrates the honey bee’s exoskeleton with its mouth parts. The resulting wound is an entry point for numerous viruses. The viruses cause a number of honey bee diseases, and their combined effect is known as “Parasitic Mite Syndrome.” While Varroa mites can be found in all honey bee hives, colonies can withstand a low level of mites. Varroa reproduce at a relatively steady rate, unlike some other honey bee pests. Small hive beetles, for instance, reproduce in massive bursts to rapidly overwhelm a bee colony.

All attempts at controlling Varroa mites should begin with seeking lines of honey bees that have a natural resistance to mites. A heritable behavior trait of resistant honey bees is described as “Varroa Sensitive Hygiene.” Bees with this trait can detect reproducing Varroa mites and remove them along with the infected bee brood. Resistant bees also preen mites from the bodies of adult bees. These mites fall through the screens of bee hives equipped with screened bottom boards, preventing reinfestation of the hive. Beekeepers can dust the bees with powdered sugar to encourage preening. If Varroa mite levels in the hive are too high, “soft” treatments using essential oils or organic acids can be used to reduce the mite levels. Each of these measures can be used together as part of an Integrated Pest Management program. While parasitic mites have killed most feral honey bee colonies, some exist, like these bees clustered for winter in a hollow tree.

--Richard

Bees in Hollow Trees

Beekeepers receive many calls from people who find bees in trees. Particularly in the spring, these are swarms of honey bees hanging from a limb. It is also common for homeowners to find honey bees living in a hollow cavity in a tree in their yard. The tree may have been occupied by bees for a long period of time, but the bees are unnoticed until warm weather brings about increased flight activity. When one receives a swarm call, it is best to quiz the caller for as many details as possible. I received a message that there were bees on a tree limb exactly seven and one-half feet above the ground. This would be a perfect opportunity to try out my new swarm collecting device that I built from a design shown on John Jones’ Stone Mountain, Georgia beekeeping blog at http://stonemountaingeorgiabeediary.blogspot.com/2011/05/swarm-catcher-5-gallow-water-bottle-in.html. The device is a plastic jug mounted on an extension pole for safe removal of bees in a tree while standing on the ground.

I loaded my truck with a swarm box, bee hive, feeder, syrup, a bee suit, veil, and tools. Next, I called to get exact directions and clarify details from the homeowner. He finally described the bees as being one cupful of bees, a rather small swarm, possibly from the colony that he had an exterminator spray inside the tree. He read out a list of three insecticides that had been sprayed or dusted on the bees plus an adhesive sealant sprayed into their nest. He asked me if I reckoned that spraying had hurt the bees, and did I want them. I told him that I had no use for dead bees. Remarkably, this was not my only call to collect dead bees. The other recent caller wanted me to pick-up dead, insecticide-sprayed bees so that they would not come back to life and harm her. Today’s photo is a swarm of live bees I collected from the surface of an oak tree.

--Richard

A Natural Honey Bee Nest

We can learn much about honey bees by observing bees in their natural habitat. Residents of my Arkansas Delta county called today and described a colony of honey bees living in a huge, hollow cottonwood tree at their home. Cottonwoods are among the tallest trees in the Delta, climbing to nearly 150 feet. This gnarled tree had weathered many a season and showed the damage of numerous wind storms and lightning strikes. Hollow cavities in storm-damaged trees provide excellent spaces for honey bees to build their nests.

The colony moved into the ancient tree this past October. Colonies that swarm late in the year often fail to build enough comb and store a sufficient amount of honey to survive the winter. Fortunately, there was a good nectar flow from goldenrod this past fall. If you click on today’s photo, you can see the entrance to the natural honey bee nest about 23 feet above ground on the underside of a large, hollow limb. Four sheets of clean, light-colored beeswax honeycomb hang down from the opening in the tree. The darkened comb previously held brood and pollen. Like a screened bottom board on a modern bee hive, the open bottom of this natural nest allows hive debris and parasitic Varroa mites preened by the bees to fall to the ground. All of the exposed comb is empty; the bees have moved their cluster upward over the winter. The empty cells filled with air make excellent insulation for the colony’s nest. The sheets of comb themselves help calm the winter winds. The homeowner and I watched the honey bees actively flying from their natural nest. An international pilot, he discussed how insecticides are sprayed inside the cargo holds of aircrafts before landing in foreign countries to prevent the unwanted transfer of bees or other insects. This colony should be successful in its new home. It found a suitable tree and a family concerned with protecting the bees and the environment.

--Richard

The Bee Tree

Memphis is a unique city. Flying over the city, we get the impression that we are over a park instead of a typical large city. The majority of the city is covered with massive oak trees. This week I got a call about a swarm of bees in a shrub in the lawn of one of the city’s one-hundred-year-old neighborhoods. The homeowner explained that this was actually the second swarm to appear in the shrub in the same week. When I arrived at her home a short time later, these bees, like the earlier swarm, had already flown away. This is the typical pattern of swarming honey bees to light on a shrub or structure close to their old cavity home. After a short period of time they move on to a permanent home in another cavity.

In Memphis, the bees have no problem finding a suitable cavity for a new home. Many of the large oak trees have cavities resulting from lightning strikes or storm damage over the years. I found just such a tree nearby. About thirty feet above, bees could be seen entering and leaving the huge oak tree through a hole in the trunk. Often we have colonies of honey bees in our own yard, sometimes for years, without our even knowing it. We share a rich natural environment with people, trees, flowers, and bees. It’s a good thing to have cities that look like parks.
--Richard