Lesson 14a – Oxilicacid – Safe and Easy in Bees but….
Dr. Ellis gave a lecture about the benefits of using oxalic acid for Varroa control, and I listened with great interest. At the end of the lecture, someone from the audience posed, “Where does one purchase this ‘oxalic acid?’” Dr. Ellis replied, “At your local hardware store. It’s wood bleach.” From the back of the room, I could hear some of the comments rising over the crowd, such as, “Wood bleach? Is he kidding us?!? I’m not putting wood bleach on my bees. It’ll kill them, for sure!!!”
I was right there with them, thinking to myself how horrible it would be for the bees. Afterward, I sat down with Dr. Ellis, and we chatted about the research that he and his graduate student Nicholas Aliano had conducted. They tested various application methods (drip and vapor) and treatment concentrations. Their results showed that oxalic was not harmful to the bees, but that it did do a number on the mites. Following that discussion, we tried it at the UGA bee lab, and we experienced the same outcome. Oxalic killed mites by the thousands! As a result, I started inquiring into getting oxalic acid registered for use as a miticide in the US, but quickly found out it was NOT going to be easy. It hadn’t been easy for the Canadians either.
Getting a pesticide approved takes a lot of time and money. It took six years from the time that the Canadian testing was completed for the registration process to move at a glacial pace through the proper channels. But, finally, the Canadian Honey Council officially registered oxalic acid in November 2010.
This brings to mind a conversation I had with Steve Forrest, former president and owner of Brushy Mountain Bee Farm, when he was trying to get Api Life Var (thymol) registered. Not only was there an incredible amount of legwork involved, but, like I mentioned previously, there’s also a huge amount of money required for testing, research, data analysis, labor, etc. Fortunately, the company that produces Api Life Var paid the costs and it was successful.
However, this was not the case for oxalic acid – a widely available, generic chemical. Think about it. Now, I’m just going to make up numbers here, but let’s say that it costs $500,000 to get a typical miticide registered by the EPA/USDA for use in bee hives. When a proprietary formula is invented, trademarks and intellectual property right protections can be obtained to secure such an investment to get the chemical approved and marketed. But who is going to put up big bucks to have a ubiquitous product approved for use in a bee hive when such an investor would have no control over its ultimate distribution, and, therefore, have no ability to recoup her/his investment? Today, anyone can stroll down to their nearest hardware store and purchase enough oxalic to treat 200+ colonies for just a few bucks.
In the mean time, the bees need our help. Varroa mites aren’t going away, and, without every safe and effective remedy at our disposal, our bees are suffering. The latest research suggests the economic threshold for Varroa is now three mites per 100 bees. In the old days, before the recently introduced viruses, small hive beetles, rising stresses from limited nutrition and growing toxin levels in the environment, upwards to 15 mites per 100 bees was considered tolerable.
So, in accordance with President Obama’s 2014 initiative on pollinator health, the EPA expedited the review on the registration process for oxalic acid. The EPA collaborated with the USDA and the Health Canada’s Pest Management Regulatory Agency to move as quickly as possible on the evaluation of oxalic acid. It takes years to research and evaluate product toxicity, exposure risks, environmental impact and transport-related issues along with effectiveness data. All of these concerns need to be addressed, analyzed and the resulting data deemed accurate and favorable before a product can be registered for safe use in the US. While these assurances are certainly good things, it just takes time – lots of time – which is why the president stepped in and said, “Ok, folks. Let’s figure out a way to speed up the process to get beneficial products to those who need them.” And that’s where Canada helped out. They had already completed the years of testing and, as part of the NAFTA “work share” agreement, they could share their data with the EPA risk assessors and managers to speed up the process; it saved years. We didn’t have to re-do all the same research. We built on what the Canadians had already accomplished. And, once all the data was reviewed, the conclusion was that oxalic acid should be registered for use in the U.S.
What is Oxalic acid? It’s an organic acid found just about everywhere in the environment including in plants and vegetables. It is bitter to the taste and irritating to the eyes, mouth and skin. It is a natural plant defense against herbivores. It is also found in honey. Since it is not fat soluble (a lipid), it doesn’t build up in wax comb. Back in 1957, it was registered as a pesticide (disinfectant/sanitizer), but, by 1994, the renewal of the product registration was cancelled.
There are risks involved if you plan to use oxalic acid. Given its caustic effect on the eyes, skin and respiratory system, it’s labeled with the highest degree of toxicity, “Category 1.” So, as with all pesticides, caution must be taken when handling it.
How can oxalic be applied? Oxalic can be applied several ways: drip (trickle), vaporization and spraying. It can be used on existing colonies, packages or swarms. The two most popular are the trickle and vaporization method. The trickle or solution method is taking the acid and mixing it with a warm 1:1 sugar-to-water solution. Next, the solution is drawn into a syringe and 5 ml is trickled (scientific term for “dribbly drop”) down the seam between each frame and directly onto the bees; the maximum dose is 50 ml per colony (5mls per seam). It doesn’t matter whether it is a nuc or a hive with a single or multiple brood chamber, but reduction in dosage for smaller colonies obviously.
The vaporizer method is only to be used on colonies outdoors. And, what ever you do, do not inhale the vapor! Basically, you use a vaporizer which is a metal wand with a plate at one end and a cord which connects to a battery at the other end. One gram of oxalic acid is placed on the metal plate. The plate is then slid into the entrance of the colony. The entrance opening and any other cracks and crevices are then sealed with the vaporizer in place to avoid the gas from escaping. Once connected to a battery, the heat from the plate causes the oxalic crystals to melt and turn into a gas (sublime). The vapor will permeate the hive. When it contacts the mites, it kills them. Each vaporizer is different. Some take only a few minutes to activate the acid, while others take a little longer. Since you don’t have to open the colony in order to treat, this seems to be the easier of the two methods to implement, especially on cold, rainy days.
You can also spray (mist) packages or swarms. Over the last few years, we’ve followed this protocol to ensure that we’re starting our research projects with mite-free bees. Once the packages arrived, we placed them in a cool, dark location in the lab for 24 hours to cluster the bees. Several hours prior to applying the oxalic solution, we spray the bees with a 1:1 sugar solution to fill their honey stomachs and reduce ingestion of the upcoming oxalic treatment. Next, we mix the oxalic acid in a 1:1 sugar water solution and evenly apply the solution to the bees.
Why use oxalic? It works. It has been used for years in Europe. According to numerous studies, it’s 90-99% effective at killing the mites with minimal damage to the bees and brood.
Does trickle or vaporization work better? A recent study at Sussex University examined the effectiveness of different doses and application methods on mite and bee mortality. The experiment involved 110 hives. The results showed sublimation (vaporization) was far better at reducing mite populations and showed no increase in bee mortality.
Is Oxalic perfect? No; it only works on phoretic mites, i.e., those mites crawling around on the frames or adult bees. The mites breeding under the cappings of the brood cells are unaffected by oxalic administrations, as well as most other miticide products. Therefore, applications are most effective when no brood is present. At beekeeping meetings, when chatting about this product to others, I’ve heard folks say that they are applying oxalic once-a-week for three weeks during the Summer months. This isn’t really advisable since it’s not very effective and can be detrimental to the bees. But there may be a way to still treat during the Summer months.
A few months ago, a group of commercial beekeepers came over from Italy to learn about small hive beetles. Apparently the beetles have crossed the border and are starting to be a problem there. During our discussion, we also talked about Varroa control and what beekeepers do in Italy. They said that they treated twice-a-year with oxalic acid vapor. They treat once in the Winter when colonies are naturally broodless, and once again in the late Summer after inducing an artificial state of broodlessness by caging their queens for 21 days. At first, I thought this was nuts, but, after we talked a bit more, it made sense.
The Italians explained that by August or September, the nectar flows are over and the colonies are about to start producing Winter bees. If mite populations are high, then the related virus loads that cause Winter mortality will be high, as well. Plus, by caging the queen, the foraging population (no longer needed) drops faster, and more colony resources (needed for Winter survival) are conserved. Why maintain a pipeline of replacement bees to sustain a large foraging force after the nectar flow is over? A hive full of bees eats regardless of whether or not there is work to be done. So, interrupting the brood cycle not only knocks down the mites (and the viruses vectored) prior to the Winter bees being reared, but reduces bee populations as well. Fewer mites equals improved health, and fewer bees equals less food consumed; both circumstances contribute directly to improved Winter survival. Yeah, I know that it is a bit of work to first cage and later release each queen, but think about the money and work it will save by Winter or next Spring!
Ok. So, now what? Brushy Mountain Bee Farm has been authorized by the EPA to be the sole distributer of oxalic acid for use as a miticide on honey bees. What does this mean? Well, in order for any application of oxalic (in beehives) to be legal, it must have the EPA approval label on it; Brushy is the only distributor registered to use the EPA label. It may seem silly, but it really is there for a reason. If you start searching the internet for oxalic acid application in bees, there’s a whole host of information out there on recipes for taking 100% oxalic acid down (wood bleach) to the 2 or 3% recommended application concentrations. Some advice may be sound, but other advice can be reckless and dangerous to you and your bees. Certainly, you don’t want to get hurt or inflict undue stress on your bees. The EPA label assures you of what you are receiving and gives you the applicable instructions to follow so that you can safely achieve the results desired without the risks of winging it after watching a YouTube video which Inwill post later.
Be good to you and your bees.
Jennifer Berry is the Research Leader at the University of Georgia Honey Bee Research Lab