For the Love of Bees and Beekeeping

November 2014

What’s next for Varroa control?

by Keith Delaplane


In my column last month I spelled out what I think is a fundamental tension facing beekeeping today: (1) controlling Varroa is priority #1, and pesticides have proven the best way to do this; however (2) it is impossible to use pesticides without getting unintended consequences in the form of non-target die-off, unknown lethal or sublethal synergies, or degradation of environmental assets. This tension can be extrapolated upward to apply to all of agriculture in general as we face the challenge of feeding 9 billion human beings by mid-century. In last month’s column I also asserted that these tensions must be resolved as co-priorities with neither one marinalized. The first part, that pests must be managed, is non-controversial. But it’s the second, environmental side of the argument that typically has the uphill battle in these kinds of discussions. What’s at stake here is the erosion of those environmental assets I mentioned, sometimes called “ecosystem services,” those free gifts of nature upon which all human enterprise depends. When I talk to farmer groups I ask them, What dollar value can you place on rainfall? soil fertility? erosion control? Well, pollinators fall into that same camp as do the thousands of beneficial organisms that combat the damaging ones. Nature is full of unsung assets like these, the value of which is not only incalculably huge but downright obligatory – we couldn’t live without them. But even though my second priority is at least as important as the first, it’s also the easiest to be set aside, given that we humans tend to favor immediate results at the expense of the deferred.

I was recently reminded of this when I read a review article on the environmental risks of neonicotinoid insecticides  - currently making headlines as both the most widely used class of insecticides in the world as well as a special hazard to pollinators. Neonics are systemic – available in all the plant’s tissues, which gives them 24/7 action against herbivorous pests but also gives them their peculiar hazard to pollinators who are exposed to the toxin when they collect nectar and pollen of treated crops. Neonics are regarded as comparatively safe to mammals and other vertebrates. They are usually applied as seed-coatings which further minimizes their contact with non-target species and reduces applicator labor. Patent expirations have rendered them relatively cheap. But it’s their efficacy that ultimately carries the day as neonics are famously effective against a wide range of insect pests. So effective, in fact, that in certain cropping systems neonics have ushered in a sort of anti-IPM backlash where their economy, ease of use, and efficacy have pushed growers away from cumbersome IPM sampling schemes in favor of chemicals to a degree reminiscent of the 1950s and 60s . Years’ worth of gains in IPM-oriented grower education and behavior modification were dropped overnight, so to speak, with the arrival of a sufficiently cheap and effective insecticide. This experience underscores the fact that any sustainable pest control scheme has to be efficacious, affordable, and practical or it will never get off the ground.

Perhaps I’m overstating things here, but I want to stress the co-priority of these two dynamics in my attempt to remove partisanship from the discussion. There’s no need for a “pro chemical” side versus a “green side” when it comes to the future of Varroa control. The winning formulas will possess the efficacy of chemicals and the sustainability of nature in equal measure. The trick is how to get there, and I’m not sure the trajectory of current research and education is sufficiently on target.

For staters, I’m not interested in a search for better or safer acaricides insofar as they are just another variation of acute toxin unloosed into the environment. If CCD and bee decline have taught us anything it’s that broad-spectrum toxins involve negative synergies and unintended consequences.

Second, my confidence is shaken in a classical IPM approach to Varroa based on thresholds. As I have written earlier, in some cropping systems the tolerable pest threshold is essentially zero. Given our growing knowledge of the tight relationship between Varroa and dangerous viruses like DWV, I suspect that our published Varroa treatment thresholds, already rather low, are still too liberal and should be adjusted downward and earlier in the year. Moreover, at a commercial level it has proven difficult for beekeepers to practice mite sampling at any meaningful scale. Should it be done at the level of colony? how about apiary? Given the inconvenience of counting mites and the importance of controlling mites it usually boils down to treatment by calendar instead of treatment by sampling.

And last but not least, I am on record expressing my ...