By William Rowe1 & Geoff Williams2
1The Alabama Cooperative Extension System, Fairhope
2Department of Entomology & Plant Pathology, Auburn University, Auburn
If you spotted our last post, you already know that our Spring hasn’t merely sprung, it’s a bear-trap whose steely jaws are clapped shut on your colonies. As a result, colony build-up is off and running because of the early nectar flows. So far we’ve advised you to consider feeding your bees to ensure that they don’t starve. Now we urge you to carefully keep an eye out for a particularly menacing creature.
Along with buildup of your bee population, and especially with those first batches of drones for spring breeding, come the Bee Ticks. If you are new to beekeeping, you may not be aware of these creatures. Just imagine something roughly the size of a Chihuahua biting your body to drink your blood. Wouldn’t take long for you to feel, um, drained.
This bee tick is more commonly known as the Varroa mite (Fig. 1). It’s scientific name – Varroa destructor – gives you an idea of its power over your honey bees. Unfortunately, we humans, by shipping around our honey bees over the last half century, have spread the Varroa mite from its home in East Asia to nearly every corner of our globe. The very few exceptions include the island of Newfoundland in Canada, the Isle of Man in the UK, and interestingly, all of Australia (there are a few other locations too). It arrived in the United States in the mid to late 1980s, and has since spread to every state.
Figure 1. A female Varroa mite on a newly emerged worker honey bee (denoted by a green arrow). Photo by G. Williams.
Varroa mites are arguably among the most important parasites of honey bees that we know of. They damage your colony by feeding on bee blood (we bug folk call it hemolymph). Not satisfied with the blood of developing larvae and pupae (Fig. 2), they also feed on adults.
Figure 2. Female Varroa mites within drone pupae cells (denoted by green arrows). Photo by W. Rowe.
Being drained of blood weakens bees, shortens their lives, and makes them more susceptible to disease. Speaking of disease, have we mentioned that the Varroa mite is a handy carrier of bee viruses? When they’re feeding on bee blood, they are, all mosquito-like, contaminating your bees with viral diseases. One of the most common signs of a high mite population is the presence of adult bees with deformed wings (Fig. 3). This is typically caused by Deformed wing virus, and likely means that it is already really late to be controlling for Varroa mites in your colonies.
Figure 3. A dead experimental honey bee worker exhibiting signs of deformed wings, most likely because of concurrent Deformed wing virus infection and Varroa infestation. Photo by G. Williams.
You just might be crying at this point in our happy documentation of what seems like a bee vampire movie. Yes, Varroa mites can be death for your colony. In fact, they are a major cause of most colony losses. Unless…
You Begin An Integrated Pest Management Program For Mites Right Now!
We just used some words, there. It’s not something you have to purchase, per se. Simply put, it’s a holistic approach to managing pests in your colonies by employing appropriate monitoring and treatment regimes, the latter of which includes using biological, cultural, physical, and chemical tools at appropriate times. And by ‘control’ we mean just suppressing their numbers. It is nigh impossible to keep bees in Alabama without experiencing Varroa mites at some point or another.
There are several methods for checking up on your mite population, and each brings its own pros and cons. We most often recommend the sugar shake or wash methods. Essentially, you can use powdered sugar or a fluid (either rubbing alcohol or winter windshield washer fluid) to dislodge mites from about 300 adult bees collected from the broodnest. Counting the number of fallen mites, coupled with some simple mathematics, will allow you to determine the percentage of mites that are infesting adult bees in your colony. Levels can vary depending upon the surrounding environment and time of year, but generally anything greater than a 3 % infestation level warrants further investigation immediately. For those of you with fewer than 10 colonies, make sure you check each of them. For those of you with more, try to get to as many as you can reasonably manage! You’ll want to do this at least 4 times throughout the year.
The most common method for controlling the Varroa mite when threshold levels have been exceeded is by using a miticide. There are currently 10 products approved for use by the EPA; each has its own unique properties and directions for use (Table 1). Remember, the label is the law! Make sure you stick to it!
Table 1. Current pesticide products registered by the EPA for use against Varroa mites in honey bee hives. Modified from the EPA. Some products may only be available under specific circumstances (e.g. emergency-use permits). Consult the EPA for up-to-date recommendations.
|Product||Active ingredient||EPA Labels|
|For-Mite||Formic acid (65.9%)||[Link]|
|Sucrose Octanoate||Sucrose octanoate (40%)||[Link]|
|Api Life Var||Thymol (74.09%), Oil of eucalyptus (16%), Menthol (3.73%)||[Link]|
|MiteAway Quick Strip||Formic acid (46.7%)||[Link]|
|HopGuard II||Hop beta acids resin (16%)||[Link]|
|Oxalic acid dihydrate||Oxalic acid (97%)||[Link]|
But it’s Spring and you want to get that fine honey. If you don’t stop the mites that spring honey might be the last you get. What to do, what to do…
Well, there are some registered mite products that you can use while the colony builds and starts storing honey as spring unfolds. These are mostly ‘natural’ treatments – Formic Acid and Hops Acids. Formic Acid is made by insects and can already be present in the hive. Hops Acids (Lupulone, Colupulone, Adlupulone) disperse quickly and break down in the hive environment without contaminating your honey.
There are a few formulations of Formic Acid available for use. That said, only 1 product is labeled for spring use while honey supers are on the hive:
MAQS (Mite Away Quick Strips), manufactured by Nature’s Own Design Apiary Products Inc. of Ontario, Canada, is labeled with the EPA as being safe for use while honey supers are on the hive. Formic Acid products like MAQS are known to cause brood death and can only be used when temperatures are between 50oF (10oC) and 85oF (29.5oC). If you decide to use MAQS, be certain you read the product’s entire label and understand the directions.
There is only one commonly sold product for Hops Acids:
HopGuard II, manufactured by BetaTech Hop Products, a subsidiary of Barth Haas Group Inc., is labeled with the EPA as being safe for use while honey supers are on the hive. The treatment is applied to the brood chamber(s), and make sure you don’t collect honey or wax from the brood chamber after treatment. This product is best used before the queen starts her egg laying in the spring, but can still be used afterwards. HopGuard II does not have the narrow temperature range that MAQS does. However, warm weather can quickly dry the treatment strips, thereby reducing its efficacy. If you decide to use HopGuard II, be certain you read the product’s entire label and understand the directions.
With a bit of luck, and a lot of careful planning, you can keep mite levels below treatment thresholds for most of the year by incorporating physical and cultural practices like drone brood removal (Fig. 4), screen bottom boards, brood interruption, and use of hygienic stock into your Varroa IPM scheme. When it comes time to treat using chemicals, don’t be a one-trick pony! You’ll only be breeding for resistant mites!
Figure 4. A plastic drone frame being inspected for Varroa mites. Once cells are sealed, drone frames can be removed from colonies to help reduce mite population levels. Photo by G. Williams.
EPA 2017. EPA-registered Pesticide Products Approved for Use Against Varroa Mites in Bee Hives (Accessed 18 March 2017).
Honey Bee Health Coalition. 2016. Tools for Varroa Management, 5th Edition (Accessed 18 March 2017).