There are a variety of external factors that can influence or increase Varroa population dynamics. They include individual colony susceptibility, outside invasion pressure, ineffective controls, and beekeeper oversight or neglect. Whatever the circumstance, Varroa population buildup might be compared to a runaway locomotive barreling down the mountainside; it’s going to continue picking up speed (increasing their number) until disaster strikes. It’s the responsibility of the beekeeper to intervene and break the mite reproductive cycle, to create a treatment window before the aforementioned disaster can occur.

Under ideal conditions Varroa mite populations double approximately every three weeks. Using this example, a colony with a population of only a 100 mites on April 15th would on July 29th, have a population of roughly 3,200 mites. The generally accepted threshold or point at which colony damage begins to occur is about 3,000 mites. Once that damage threshold is reached, colony viability starts to decline. If left to grow unchecked the rapidly increasing Varroa population will send the colony spiraling into an irreversible decline. To be effective treatment must begin before that point of no return is reached. The solution to this dilemma is to remove the early honey crop as soon as possible, preferably by the end of July. Only then can the actual degree of mite depredation be ascertained, and, if necessary, treatment applied.

Once the crop is off, samples should be taken to determine the mite population density and the time frame in which any treatment must be applied. Unnecessary treatment with Apistan®, CheckMite®, or one of the IPM products is not only a waste of time and money, but increases the chances of mite resistance to that chemical. Varroa populations can and often do vary tremendously from colony to colony within the same yard. Sampling prior to the application of any controls is essential to any mite management program.

There are three commonly used methods of sampling for Varroa: 1) sticky boards via the use of a screened bottom board; 2) the sugar roll which uses powdered sugar to dislodge the mites; and 3) the original ether roll. Sticky boards work fine if the colonies are all close to home. If not, a lot of valuable time will be wasted traveling to and from the outyards. Sampling potential breeder colonies is the one exception. Here the extra time and effort required with sticky boards is well justified. Sugar rolls have received a lot of favorable press, but I’ve never been able to duplicate the reported results. Trying to count mites covered with powdered sugar can test anyone’s patience, particularly a harried beekeeper. In my opinion the ether roll is the most practical and efficient testing method currently in use. While not perfect, ether rolls are quick and easy, and once you master the technique, fairly accurate.

The standard ether roll recommendation is to collect 300 bees in a quart mason jar, spray in some starter fluid, and shake the jar for a couple of minutes. You then remove the lid, pour out the bees and count the mites on the inside of the jar. Based on personal experience, I think it’s unrealistic to expect an accurate mite count using that many bees. The main problem, from my experience, is that by shaking the jar for so long the dead bees are continually re-acquiring the dislodged mites adhering to the jar wall. It’s also a very time consuming process, and by the end of the day your arm is ready to fall off.

A much quicker and far more accurate ether roll can be accomplished by cutting the above procedure in half. Replace the quart jar with a wide mouth pint mason jar, and reduce the number of bees to 150. (To acquire the 150 bees you’ll need a quarter-cup measuring cup and a collection pan. Telescoping outer covers will work, but a small Rubbermaid tub with rounded corners works best. Simply remove a frame of brood, without the queen, and shake the bees into the tub. Bounce the bees into one corner of the tub and scoop up a quarter cup. Gently wiggle the cup to level the bees then dump them into the jar. One quarter cup of bees equates to between 145-160 bees.) The real trick is in the amount of ether used. A quick squirt is all that’s required. You barely want to get the bees wet. If you can see obvious signs of moisture most of the mites will stick to the bees and the count will be useless. The second trick is to hold the jar on its side parallel to the ground and shake it with an up and down motion. Shake for 10 to 15 seconds, then turn the jar upside down and let the bees fall into the jar lid. Carefully unscrew the lid so as to retain the bees and count the mites on the inside of the jar. Remove the visible mites from the jar, then dump the bees back in and repeat the process. Combine the two counts and treat as necessary. This technique takes practice to master, but in time it will become second nature, and the repeat roll will be unnecessary. Standard treatment recommendations based on mite counts using 300 bees are still valid. Simply divide the mite number in half and treat accordingly. The threshold I use, mid-Summer, is I will treat a colony that produces five (5) mites from an ether roll. That’s not many, but it’s enough.

There is a growing list of mite control products coming online. It seems as though a new product is being introduced every couple of months. The problem is that beekeeper familiarity and acceptance lags way behind any new product introduction. This results in the same old status quo; Apistan® and CheckMite® remain the primary mite control treatments. It’s no wonder colony losses continue to pile up as mite resistance slowly erodes product effectiveness. It’s time beekeepers wake up to the fact that mite control is a continually evolving process. Old methods, treatments and timing should be replaced by new, safer, less contaminating products, and better timed applications. Not only will residues be minimized or eliminated, but the end market commodities of honey, pollen, and beeswax products will retain their natural wholesome appeal.

The following is a quick review of the most recently introduced IPM products. I urge you to give one or more of them a try. There is a definite learning curve with each of these products involving both timing and application technique. Don’t wait until your current treatments regiment fails to investigate and make the necessary changes.

Sucrocide is a sugar ester; it kills Varroa by coating the mite and suffocating it, an effect similar to an orchard oil spray. Sucrocide has no effect on tracheal mites. Application is achieved by spraying the water diluted solution directly onto the adult bees. Depending on the number of colonies to be treated either a hand sprayer or a garden type pump sprayer can be used. Each frame has to be lifted up and sprayed. The product has to come into contact with the Varroa mites to be effective. Complete wetting of the adult bee population is required for maximum control. Three treatments at seven to 10 day intervals are necessary to kill the mites emerging form the brood cells. Application can occur anytime the ambient air temperature is above 55°. This product might be the treatment of choice for small colonies such as Spring or Summer splits where there are a limited number of frames to be sprayed. To treat large numbers of colonies refer to the July, 2005, American Bee Journal.

The active ingredient here is formic acid which produces a corrosive vapor that kills Varroa by breaking down the mite’s cellular structure. Formic acid vaporizes when exposed to air thereby acting as a fumigant. To apply this product correctly, read and follow all the label instructions. There are specific temperature ranges applicable for the proper application, again follow all label instructions.

This is a very corrosive product and appropriate handling precautions are required. Carefully read and follow all the label instructions. In actual use formic acid kills not only Varroa, but tracheal mites as well. If used properly, Mite Away II gives an average 90% Varroa control and 100% tracheal mite control. Unlike the other IPM products, Mite Away II requires only one application; there is no need to re-treat at weekly intervals.

This was the first thymol based product to reach the U.S. market. The major active ingredient is a pharmaceutical grade crystalline thymol. Fumigation is the means of dispersal. When exposed to air, the thymol crystals vaporize to form a heavier-than-air gas. This product should be used when the average daily temperature is between 65°F and 95°F. Three treatments at seven to 10 day intervals are required for maximum control. When properly applied control rates approaching 95% can be expected. Again, follow all label instructions regarding the timing of the treatments and the suggested wait time prior to honey super installation. Unfortunately this product currently has a section 18 emergency registration and may not be available in all states. Hopefully, this will change by early Summer with the approval of a section three general use registration.

This thymol product is formulated as a slow release gel and is packaged in an individual 50g tray with a peel off cover or in a 6.6 lb. bulk package. Apiguard gives off a foreign odor which the bees try to remove. Distribution of the gel depends on the house cleaning bees transporting it around the hive during the removal process. Apiguard kills Varroa by disrupting the mite’s cell membranes. It also has some action against tracheal mites and chalkbrood. Apiguard can be used anytime temperatures are between 59°F and 100°F, the warmer the better. Two treatments at two week intervals are required for maximum control. The second treatment should be left on for up to four weeks, or as long as any gel remains. When used according to the label instructions Apiguard gives a Varroa control rate of between 85 and 95%, with an average kill rate of 93%.

Oxalic acid has not yet been approved for use in the U.S. It has however been approved in Canada and Europe. Registration in the U.S. is currently in progress. Application is achieved by using a veterinary syringe to trickle 50 cc of the dilute oxalic solution between the frames of the active broodnest. The bees come in contact with the mix and spread it through direct body contact. Current recommendations are to use this product at the end of the season when brood rearing is at a minimum, or has ceased entirely. Mixing and application instructions are available online at www.honeybeeworld.com – click on Varroa formic acid, then oxalic acid trickling.

Mechanical control is another option worthy of consideration in the battle against Varroa. Mechanical control being defined as short term Varroa control without the use of any mite control regimen other than selected stock and colony manipulation. Stock selection can play a significant role in the management and control of Varroa. Varroa reproduces in the capped brood. If the amount of brood can be controlled or managed after the main honey flow, the Varroa reproductive cycle can be disrupted. Instead of using a prolific Italian stock you might want to consider a more conservative Carniolan or Russian line. Reducing the size of the broodnest prior to the main honey flow can also have a negative effect on Varroa reproduction. This management strategy also reduces the populations of welfare bees that do not contribute anything towards the honey crop.

The makeup of Summer splits also has a negative effect on Varroa populations. Nothing of significance changes with the parent colony, but the split ends up with a much smaller Varroa population. The Varroa buildup process has to start all over. The necessity of queen introduction further disrupts mite reproduction. As Fall approaches and brood rearing continues to decline, Varroa cannot maintain its rate of increase. Put another way, splits made in mid July in northern climes only have time to rear three cycles of brood before cold weather halts the proceedings. Mite populations don’t have enough time to build up to the point where colony injury ensues. In practice, Summer splits in this area rarely require any mite treatment prior to the onset of Winter.

Local beekeeper and good friend Mark provides another example of mechanical Varroa control. Mark runs most of his colonies in a single brood chamber year round. While this type of management has some limitations, it bodes well when it comes to Varroa control. Mark was kind enough to check his yard records regarding mite control treatments and their dates of application. It should be noted that Mark routinely samples for Varroa using the ether roll method described above. No treatment is applied unless the ether roll indicates there is a problem. (Treatment is initiated when the 150 bee ether roll shows a mite load five or more.) Mark treated everything in October of 2005 with CheckMite® once the majority of the samples reached the treatment threshold. According to his records, the previous treatment was with Apistan® and it was applied in early May of 2003. Again everything was treated at that time. That’s two and a half years without any treatment. No special stock, Russian, SMR, or hygienic bees are in use. Yet the Varroa counts have remained very low for an extended period of time.

There are no commercial operations in this area. The two or three sideline beekeepers operating in the same area as Mark are all responsible individuals. They all have a healthy respect for Varroa and routinely sample and treat as necessary. As a result outside invasion pressure, a common source of Varroa infestation probably isn’t much of a factor. But that alone can’t explain the low mite counts. Something else is at work. Obviously the small broodnest comes into play, but how? As Mark would say, 'The small broodnest reduces the size of the Varroa incubator, hence the mite’s reproductive capacity.' I think Mark is partially right, but it can’t be that simple. If it were, Varroa would be but a footnote on the pages of beekeeping history. Perhaps some enterprising young grad student could help supply an answer to this question.

To achieve proper Varroa control you need to create a window of opportunity in which to apply the necessary controls. This is accomplished by removing the Spring honey crop as soon as possible. Once the crop has been removed sample each colony, or take a representative yard sample and treat accordingly. Instead of routinely treating with Apistan® or CheckMite®, consider using one of the IPM products. Take advantage of whatever time is left before the old standbys fail, to familiarize yourself with these new treatments. Last of all, you might want to consider experimenting with some form of mechanical Varroa control. Not only will you lessen your dependency on chemical controls, but you may also improve some of your beekeeping skills in the process.