Honey Bee Biology

Honey Bee Biology  - July 2015

 

How Adult Small Hive Beetles Can Destroy

Honey Bee Colonies by Themselves

by Dr. Wyatt A. Mangum

(excerpt)

In the previous article, we covered basic small hive beetle biology. This article concentrates more on protecting colonies from small hive beetles and showing how just the adult beetles can destroy small-sized colonies.

Keeping colonies strong is the general recommendation for protecting them from small hive beetle invasion of their brood combs. However in the current complicated world of bee management, plagued with miticide-resistant varroa mites, hindered by failing queens, fraught with bee diseases and pesticides, keeping colonies strong is not always possible. Beetle populations may flare up at the worst possible times when the colonies are weak and vulnerable – hence my recommendation for routine colony inspections, at least once a month.Those inspections should continue all through the summer dearth.

A colony inspection should go down to seeing the trash, if any, on the bottom boards. Just look on the hive floor when a couple of frames are out of the brood chamber because beetle larvae hide in the trash. Make sure the brood nest size is adequate for the recent past and present nectar flow conditions, figured from past seasonal experience and observing the currently healthy brood nests of other colonies. Let-a-lone, “lazy,” and let-nature-take-its course so-called “beekeeping” methods are not appropriate in times of small hive beetles, varroa mites, etc. Beekeepers should inspect their colonies. These inspections need not be massively disruptive. With learned skill, one can open a hive, quickly inspect the colony, and close the hive, before disturbing the bees too much or arousing robber bees.

When colonies become weak in the summer, expect the appearance of beetle larvae, particularly in areas where this pest is present. In Figure 1 we see one of my colonies that became weak in summer heat. Small hive beetle larvae invaded quickly. Those larvae congregate on the hive floor and invade other combs. Thousands of beetle larvae amass in the back corners of the hive away from the light (see Figure 2). The material that appears slick and shiny is the slime the beetle larvae produce. This slime is also found on the combs contaminated by the larvae. Between the wax moths and small hive beetles, the combs decay to eventually a thick black layer of detritus covering the hive floor.

My rule is not to keep colonies in the summer that are weak. I unite weak colonies with other weak colonies or to strong colonies, depending on the original cause of the colony becoming weak. Typically these are colonies whose populations are decreasing and cannot cover all of their combs. The original cause of the colony becoming weak could be a failing old queen or colonies being destroyed by too many varroa mites, or even colonies greatly weakened by excessive after swarming from the spring. These conditions can be corrected if detected early on by a routine colony inspection. Particularly in out-apiaries, located away from the house, not watched frequently, such weak colonies can die, and turn into beetle factories, rearing many thousands of them. Understand however, even with the best beekeeper management, colonies will likely experience small hive beetle immigration from outside of the apiary. The beetles can originate from neighboring feral (unmanaged) colonies expiring in the summer.

One summer, I was called to a wood processing facility where large logging trucks bring cut trees for processing. Somehow they cut and loaded a “bee” tree on one of the many in-coming trucks. When the truck hauling the hot one stopped on the scales before unloading, some bees came out and apparently made a mess of their paper work. The work crew managed to unload the bee tree by itself, away from the hundreds of other trees. Eventually my phone rang. Arriving on site, I saw the bee tree lying on its side after a brutal truck ride. It was after the spring nectar flow. Typically the heavy honeycombs would have scattered, drowning the bees. I figured the colony was probably dead. The few dozen bees circling the tree were merely lucky survivors, their fate delayed. So I did not mind going up to the tree with only a smoker, the other protections a hindrance (not recommended), but I did approach the tree from downwind. (The tree crew thought I was crazy.) When the top of the tree was cut off, the blade cut into the upper part of the hollow, but not into the combs, which began lower down. As I shined my flashlight into the hollow, I did not see bees or comb, the usual sight since I was a kid hunting bee trees. Rather I saw the new reality – a slimy brown glob of thousands and thousands of beetle maggots, white and seething, in constant motion. This was not a bee tree. It was a – beetle tree. Of course, we surmised that was happening out in the woods, but seeing it was a visceral experience. (Also similar to varroa mite immigration increasing in a summer dearth, I would expect small hive beetle immigration to follow a similar pattern, both of them increasing when times are difficult for bees.)

A stunning version of adult small hive beetle immigration occurred in the summer of 2014. I had planned some queen introduction experiments in my bee house, which can hold 30 single-comb observation hives. Usually I have 20 – 30 full size colonies around the bee house, which I use for queen rearing and other projects. Last summer my out-apiaries had all the full size colonies, leaving only about eight observation hive colonies in the bee house to endure adult small hive beetle immigration. July is good time to conduct queen introduction experiments. The dearth occurring at that time makes queen introduction more difficult, which provides a worst-case scenario to overcome.

By that time, my best observation colonies were queen right and covering their combs with normal brood nests and old enough from the spring to be in a “stable” age distribution. In many respects, these observation colonies function like a miniature version of a large colony. In addition, given their small size, think of these observation colonies as mating nucs for rearing queens or possibly very small splits for eventually growing new larger colonies.
The first big symptom of a problem came with too many ...

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