Sometime in the early 1960s in the Philippines, a tiny mite that fed exclusively on the eastern honey bee (Apis cerana) encountered a new honey bee species – Apis mellifera, the western honey bee. The mite latched on, and the rest is history.
This is of course the story of Varroa destructor, THE major problem for beekeepers and what all of us spend a lot of time worrying about. “If you don’t worry about Varroa, you’re either wildly ignorant or not a beekeeper,” I was recently told by a colleague. Very true.
Unfortunately for us, our western honey bee has not lived for a long time in the wild with Varroa. Thus, it harbors a small fraction of the defenses necessary to effectively combat Varroa. So that’s where we as beekeepers and scientists and entrepreneurs and all-around tinkerers have stepped in. Over the past ~30 years, we’ve used knowledge, skill, hard work – and occasionally pure luck – to develop dozens of Varroa control tools. Where does luck come in? This is the topic of our fourth “Notes from the Lab”, where we highlight “Lithium chloride effectively kills the honey bee parasite Varroa destructor by a systemic mode of action”, written by Bettina Ziegelmann and colleagues and published in the journal Scientific Reports [8:683 (2018)].
To understand their study, we first need to understand what happened before the study. The authors were working on something called RNA interference (or RNAi, for short), which is a nifty way to target pests like Varroa. Basically, you find some genes that are essential to the survival of an organism (for example, genes that allow Varroa cells to divide and grow), then introduce some RNA that interferes with those genes (hence why the approach is called RNAi). A major advantage of this technique is that you can target multiple genes that are unique to Varroa. In other words, the RNA will be bad for Varroa but will have little effect on other organisms that we like more than Varroa (e.g. our western honey bee).
This is what the researchers were playing around with when they noticed something really interesting. They exposed Varroa to some of the “bad” RNA and noticed that all the mites died. But they also exposed Varroa to some “whatever” RNA that should have had no effect, and all the mites still died.
After scratching their heads for a while, the researchers realized there was one thing in common between each of their RNA experiments. They had used lithium chloride to produce both the “bad” and “whatever” RNA that they used in the experiments. So, being astute researchers, they conducted a third experiment and exposed Varroa to only lithium chloride. Low and behold, all the mites died.
What about the bees? Does lithium chloride kill them, too? This is partly what the authors’ study is about. Over several follow-up experiments, the authors show that ….