For those of you unfamiliar with Karin’s work, she is a researcher at the Laboratory of Apiculture and Social Insects (LASI) at the University of Sussex. This is the largest research group in the UK studying honey bees and other social insects. She also works as an ecologist with her husband Steve Alton at their company FlowerScapes, selling wildlife seed mixes and advising organisations on beautiful habitat creation and wildlife gardening solutions informed by the latest ecological research. You can follow her on Twitter at @KarinAlton.
So Karin certainly knows her stuff. But she really shook up us beekeepers when she posted the following advice on Facebook:
“hello! Latest research results from LASI indicate that between the dates of 10th december and christmas is the optimal time for oxalic acid treatment. Please check for sealed brood and destroy any, say, 48 hours before applying acid.”
Eek! We were all unsettled. Since I have started learning beekeeping the advice I’ve been given has been to apply oxalic acid as close to the winter solstice as possible (December 21-22), as that is when a bee colony in the UK is thought most likely to be broodless. And the older experienced beekeepers who I’ve learnt from drizzle that oxalic over as quickly as possible before whipping the roof back on.
So based on LASI’s research, Karin is proposing two revolutionary things:
1) The best time to treat with oxalic is as early as 10th December up to Christmas
2) Sealed brood should be destroyed a day or two before applying the acid
Of course we all had lots of questions for her, and there are currently 55 comments on the post. Some further explanation and advice from Karin:
“it’s a fallacy that you can’t very quickly check for brood, we have opened hundreds of hives (very quickly- talking here couple of seconds) without any probs, even in cold, snowy January.”
“if you want to use oxalic acid, you MUST destroy brood before, as varroa hide in sealed brood, so waste of time and money putting OA on”
“Between 10th dec to 24th [in the UK] is the time with least likely/fewest sealed brood. uncap brood 48 hours before application, you would not need to pull out every frame, in fact you can tell by shifting the frames slightly if there is any, should be very few. if you use dribble method, you dont pull frames out anyway.”
I asked about timings, as me and Emma can only really get to the hives at the weekend, and Karin suggested that:
“Emily, may I suggest you pop to your hive first thing Saturday morning, and work fast, you don’t pull every frame out, but first take outside frame out, move others one at time, should be easy to check without waving them about in fresh air.
Start from middle frame, most likely here may be a small patch of brood, uncap with hive tool, quick slide check of other frames, then lid back on. On Sunday afternoon, take lid off, quick look to see the bees didn’t recap brood, then dribble OA. If you cannot do this procedure, use other varroa method. As I already have said, no point exposing bees to another chemical, if you leave Varroa in sealed brood! Hope this helps.”
As Karin says, “The research is being written up. All I can do is to inform you our findings, what you choose to do with this info is of course entirely up to you.” She also advises that fumigation is by far the best method, as the vapour permeates the frames. You just need the right equipment, especially a good quality mask.
The National Bee Unit currently offers limited guidance on oxalic acid in their Managing varroa booklet: “Ideally needs broodless conditions; 90% average efficacy possible; sugarless solutions have poor efficacy; danger of significant colony weakening; more scientific trials needed; highly toxic by inhalation, ingestion or skin absorption”. I think part of the reason for the limited printed advice is that the legal position relating to the use of what are termed ‘generic naturally occurring substances’ such as oxalic acid is complex. Generally the NBU inspectors are willing to give more advice on it in person.
What do you think, is destroying sealed brood a tactic you’re willing to try? I must admit I’m a bit nervous about it, even though I can see the benefits of destroying every last one of those mites. I think part of the reason for that is that I want to nurture life rather than destroy it. But then again we destroy brood during the shook-swarm in spring, and the bees bounce back strongly from that.
I’ve written a few posts before featuring advice from Karin, she is a no-nonsense lady who always has plenty to say:
- A Future Without Bees – a talk at the Southbank Centre (June 2013)
- A few titbits (a photo of Karin’s human-sized varroa mite)
- Research on honey bee health and well being (March 2013)