I got a nasty sting yesterday. In the first 15 seconds, I exhausted every cuss word I know. Then I began to worry about how I would type without using the letters C, D, or E. E is a killer.
Of course, I was being stupid. I should have remembered that a yellowjacket in a net is not a contented creature. I had been scooping up yellowjackets that were bugging my hives, and each time I caught one I held the net up to the light to make sure that my victim was not a bee. The last time, when I grabbed the fabric without looking, I became the victim.
I’m with Aristotle on this one. He believed that wasp stings are worse than honey bee stings. After yesterday, I’m convinced he was right. In comparison, I hardly notice a honey bee sting, especially on a finger. But the pain from this yellowjacket lingered all afternoon without leaving the slightest mark or red spot.
The world authority on insect stings
When it comes to stings and how they feel, the world authority is Justin O. Schmidt. As many of you know, Schmidt is the entomologist who allowed himself to be stung by a vast array of insects in order to categorize the relative effects of their stings on human beings. From these experiences he developed the “Pain Scale for Stinging Insects,” divided into three parts: ants, bees, and wasps.
When I consulted these charts after getting stung, I found that he rates the pain level of both the honey bee and the western yellowjacket at 2. That’s when I took sides with Aristotle.
Now the book
In spite of this slight disagreement, I love Schmidt’s new book, The Sting of the Wild: The Story of the Man Who Got Stung for Science. The book is fun to read and I’m learning more about stings than I ever thought possible.
Entomologists are some of the funniest people I know, and books by entomologists nearly always make me laugh. They know they are strange, but instead of fighting it, they embrace it. Schmidt is no exception as he shares vivid accounts of his encounters with armed insects from all over the world.
But as amusing as it is, the book is serious science. Part autobiography and part biology, the book covers the why, how, and when of insect stings as well as tidbits about behavior and lifestyle of all the insects he covers.
The last chapter, “Honey Bees and Humans,” explains our love/fear association with honey bees. In this chapter I learned that the main component of honey bee venom is called melittin, a substance composed of 26 amino acids that is found nowhere else in nature. Melittin destroys red blood cells, causes pain, and is toxic to the heart muscle. And that’s just one component; the list of ingredients and how they affect the human body is downright scary, but fascinating too.
A perfect late-summer read
So if you are looking for something to read while wasps and hornets are circling your picnic table, and ants are marching in unbroken lines up the legs of your hive stands, this is the perfect entertainment. And after you get through the science, you can enjoy Schmidt’s wonderful descriptions in the Pain Scale. “Apis mellifera: Burning, corrosive, but you can handle it. A flaming match head lands on your arm and is quenched first with lye and then sulfuric acid.” You get the idea.
The furry leafcutting bee, Megachile perihirta, is one of my favorite pollinators because it is large and showy. From a distance, this bee could easily be mistaken for a honey bee. But up close, it is hard to miss the large abdominal scopa where the leafcutting female carries her pollen load.
About the size of a honey bee, these bees are native to the western parts of North America. They are summer visitors, often seen in July and August. Although they forage on many different plant species, they have a preference for flowers in the Asteraceae family.
Like all leafcutting bees, the female of this species cuts round sections of leaves and petals to line her nest and build divisions between the egg chambers. Although many leafcutting bees nest in hollow reeds and beetle borrows, this species prefers underground tunnels.
I wasn’t able to photograph a male, but the males have distinctive white “mittens” on their forelegs and a white face. Soon after they mate, the males disappear for the year and the females begin to work at provisioning their nests.
The open-centered dahlias that I mentioned in a previous post turned into a playground for these bees. The leafcutters work fast, flit around in the flowers, and pose beautifully. Yesterday, my camera sounded like it belonged to a fashion photographer. As the bees strutted around on their flowery runway, and I just kept snapping away, trying to capture the perfect expression.
A pile of abdomens. That’s about all I have left of this small honey bee colony. My first thought was to blame the shrews, but shrews don’t seem to fit the situation. On the other hand, maybe there is more to shrew-dom than I ever thought.
This colony, on hive stand #1, was an April split from colony #3. Colony #3 had overwintered and was building up fast in early spring. Because I thought it might swarm, I decided to split proactively. At the time, I failed to find the queen anywhere, so I just made sure that both halves had lots of eggs and young larvae. I figured they could sort it out by themselves.
Note that the new split was housed in equipment that had been scraped, cleaned, and stored in the barn over winter. The frames were filled with drawn comb that was free of moths or any other visible wildlife.
A week following the split it was clear the queen had remained in the original hive. Hive #3 had even more eggs and #1 had none. I added another frame of brood to #1 and soon the new split was queenright with plenty of young larvae.
Four to five weeks later, toward the end of May, I noticed reduced activity around the hive. On inspection I found brood, but not much. The queen, although present, was performing poorly. I re-queened the colony and tried again.
Within a week the queen was accepted and the colony seemed to rebound. The queen was laying and the foragers were hauling in pollen and nectar. In a few more weeks I was able to add a medium over the deep. I believed the problem was solved.
And then came August
Around the first of August, the colony once again seemed to fizzle. On inspection I found a cluster of adult bees spanning about five frames, no queen, no brood, no sign of laying workers, nor any obvious signs of disease.
At that point I decided to combine the colony with another. We were in a dearth, I was fresh out of available queens, and I figured this colony was not to be. I ended up putting the remaining bees back on hive #3.
The only evidence is a pile of abdomens
After combining the hive, I removed the equipment from the hive stand to store it for winter. It was then that I found the abdomens. The bottom board was amazingly clean. There was the usual hive debris under the cluster, but one back corner was empty except for a few dead bees and a pile of shiny abdomens. I was totally baffled.
The only thing I know of that leaves piles of abdomens is shrews. But from what I’ve read, shrews are a winter problem, not year-round residents. Since I put the hive together in April, I can’t figure out how shrews could show up. Or maybe shrews had nothing to do with it.
So there you have it: a postmortem with no answers. If anyone has seen this before or has any ideas, I’d love to hear from you.
Trying to find plants that bloom in summer and fall can be a challenge. Not only do the honey bees have trouble finding forage, but even the native bees can come up short during the summer dearth. This is especially true in areas where native plants have largely been replaced with exotic species.
Last fall, Ellen Gehling, a beekeeper living here in Washington state, offered to send me a selection of open-centered dahlias which her bees love. I’ve never been a fan of big showy dahlias that look like garish dinner plates, but I had heard from other beekeepers that the simple, open-centered varieties were bee favorites. So “Yes!” I said. I was eager to try.
Tubers in the mail
Ellen sent a well-packed and labeled box of tubers along with detailed instructions about planting and growing. My husband built a raised bed just for the project, and I planted according to the instructions. Now, in the heat of August, I have a gorgeous display of flowers that the pollinators love. Not just bees, but also hover flies, skippers, and some solitary wasps have descended on the blooms. In fact, so many pollinators visit that the crab spiders have staked out their territory as well, taking advantage of anyone not paying attention.
For pollinators, the difference in dahlias has to do with the central disk. The central disk is where the pollen is produced and where the bees can access the nectar. Highly bred dahlias can have so many layers of florets that the pollinators cannot even find the central disk. Those varieties are of no interest to pollinators and are left alone in the garden.
I’m grateful to Ellen for showing me a new way to look at dahlias. Without her guidance and generosity, I would not have considered dahlias for my pollinator garden. Now they will be a regular feature.
Last week I reminded readers that an oxalic acid dribble was a viable alternative to vaporization. I also said that, personally, I was unwilling to purchase and store all the paraphernalia that is required, such as the vaporizer, 12-volt battery, and respirator. After all, I keep a small apiary that never exceeds 15 hives. For me, the dribble method is fast, easy, economical, and effective.
However, after a series of communications from various readers, something occurred to me. Many of the people who purchased the equipment were defending their choice by saying it would last a long time, and in any case, now they had everything they needed for reliable mite treatment and they wouldn’t have to purchase anything else.
That’s when it hit me: Many of those people have no intention of using anything but their vaporizer for Varroa control. Mites can be checked off the list. Problem solved.
Or is it?
What some beekeepers are forgetting is that oxalic acid, no matter how it is applied, needs to be rotated with other mite control products. This simple step is the only thing that can delay the inevitable resistance that mites will develop to oxalic acid or any other product.
Living things vary in their ability to develop resistance to chemicals, diseases, and environmental conditions. Some, like cockroaches and mosquitoes seem to evolve overnight, and the pesticides that worked wonders last year won’t touch them this year. Other species—and honey bees are a good example—change much more slowly. The speed and efficiency of these changes is genetically controlled, and it is the same basic phenomenon that gives us antibiotic-resistant diseases such as MRSA.
From what we’ve seen so far, Varroa mites are more like roaches than honey bees. One by one, they have become resistant to various chemical controls, and resistance to the newest treatments will come in time. Oxalic acid is no exception.
After a treatment of nearly any poisonous substance, a few survivors remain. These resistant survivors reproduce and raise resistant or partially-resistant offspring. After a few more treatments of the same substance and and few more generations, all the offspring will be resistant to that substance. Only by killing those resistant individuals with other chemicals can we break the chain of resistance. Simply put, to preserve the ability of pesticides to work in the future, they have to be alternated today.
EPA advice on oxalic acid and resistance to miticides
The Environmental Protection Agency (EPA) label for the use of oxalic acid dihydrate in honey bee colonies is very specific about resistance. It reads as follows:
RESISTANCE MANAGEMENT: Oxalic acid’s mechanism of action is unknown at this time. Any Varroa mite population has the potential to become resistant to acaricides. Resistance development is affected by both the frequency of application and rate/dose of application. Continued reliance on a single class of miticide or single miticide with the same mode of action will select for resistant individuals which may dominate the mite population in subsequent generations. In order to prevent resistance development and to maintain the usefulness of individual insecticides it is important to adopt appropriate resistant management strategies.
To delay resistance:
When possible, rotate the use of miticides to reduce selection pressure as compared to repeatedly using the same product, mode or action or chemical class. If multiple applications are required, use a different mode of action each time before returning to a previously-used one.
Base miticide use on Integrated Pest Management (IPM). This includes proper pest identification, monitoring for locality specific economic threshold and economic injury levels, record keeping, and utilizing all available control practices (cultural, biological and chemical).
Maximize efficacy by following all label instructions including dosage and timing of application.
Tips from Randy Oliver
In the section of the EPA label titled “Directions for Use” we are told to “Consult state guidelines and local extension experts for monitoring protocols and thresholds for treatment.”
No one even knows for sure what the mode of action of OA is against varroa, nor how it is absorbed. And no matter, I can assure you that some mites will be more resistant than others, which implies that some degree of resistance is possible. Remember, there is only a small margin of safety between the dose that kills mites, and the dose that kills bees. That means that varroa only needs to develop a slight degree of resistance until OA is as toxic to the bees as it is to the mites. Rotate treatments!
In other words, as mites becomes resistant to oxalic acid, we cannot simply apply greater and greater dosages. If we do, we will soon reach the dosage that takes down the bees as well as the mites.
Modes of action
Both the EPA and Randy mention the mode of action as being a factor in determining chemical rotations. According to Wikipedia, “A mode of action describes a functional or anatomical change, at the cellular level, resulting from the exposure of a living organism to a substance.” So basically, the mode of action is the way in which a chemical pesticide kills the mite.
The directive in the EPA label is to rotate between pesticides that have different modes of action. When I read this, I immediately wondered how a typical beekeeper, myself included, could easily identify the mode of action of any particular substance.
I passed this question on to Randy. Although he didn’t elaborate, I gathered from his answer that he favors alternating those that are organic acids with those that are not. So even if we don’t know for sure the modes of action for any particular substance, we can assume that acids behave similarly to each other, as do members of other groups, such as the phenols.
For example, oxalic acid and formic acid are both acids so we can assume they behave similarly in the cell. Perhaps the same is true for hop beta acids, but little is known. There may indeed be additional modes of action within these substances but, at present, we don’t know that either. Thymol, on the other hand, is not an acid but a phenol. So in Randy’s practice, he alternates between oxalic acid and a thymol-based product. He also suggested one could use Apivar (a synthetic miticide) as a third alternative if he or she were not opposed to such products.
Randy’s take on this makes eminently good sense, and I was dumbstruck to learn that I was doing it wrong. All along I’ve been meticulously alternating between different products, but they were products with the same (as far as we know) mode of action.
It’s up to us to treat responsibly
I urge all of you to take the subject of mite resistance seriously and never use the same treatment two times in a row. If you treat twice a year, for example, you need to use two different treatments having two different modes of action. It is fine to use your vaporizer as long as you alternate its use with another product.
An oxalic acid vaporizer is the “gotta have it” piece of equipment right now. But if beekeepers begin using it for every consecutive treatment, it won’t be long before it becomes as useless as a tanging pan.
A final note
The above analysis is based on my own interpretation of the official EPA label and Randy’s reporting at ScientificBeekeeping.com. At the very least, everyone who uses oxalic acid in a beehive should be thoroughly familiar with the official label. In addition, a careful study of Randy’s work will clarify most oxalic acid questions. Please take the time to read both.