Varroa Testing & Treatment

By: Wil Montgomery

This article originally appeared in the Spring 2018 issue of BEEKeeping Your First Three Years

An IPM (Integrated Pest Management) plan to reduce the Varroa mite population is a must these days. We have been fighting Varroa since 1987 when they showed up in the USA. All manner of miticides are available. Some are good and others are harmful to bees after long term usage. Coumaphos and Fluvalinate are being phased out since the mites have developed resistance to these miticides. They probably work to some degree, but there are several new chemicals and methods to apply that are helpful in reducing the ‘mite count’ in your hives.

One of the big problems with the above mentioned miticides is that they leave residues in the wax. Beeswax is a fatty acid and tends to collect hard chemicals. We now have what I will call ‘soft’ chemicals available and some newer compounds are not harmful at all if used properly and not so often that they could affect the functions of the honey bee.

One of these is Thymol which exists naturally in – guess what – nature. Hops is another one.

There are a few strips available that kill mites and not the bees. Look for ads on them in the bee journals.

These strips are placed in the brood box between the frames and left in for specific periods of time. Read the label, always read the label first and follow its directions to the letter.

Testing For Mites

There are three acceptable and highly useful methods to test for mites. The most obvious sign of Varroa is DFWV deformed wing virus. All of these require collecting 300 bees from the brood area of a hive. The most accurate way to test for mites is the alcohol wash. Make yourself a wash jar. Go to a fabric store and purchase the plastic mesh used for needlepoint sewing. It has about 1/8th inch openings. Cut this to fit the lid on a pint mason jar. To test bees, take the jar to the bee yard, along with a 9″ x 12″ plastic dish pan and a half cup measuring spoon. Open the test colony with as little smoke as possible. Remove a frame from the center of the brood nest with lots of nurse bees. Make certain the queen isn’t on the frame. Thump the frame in the pan, knocking off most of the bees. Scoop up a solid half cup of bees and put in the jar and quickly replace the lid. Pour enough alcohol into the jar to cover the bees. Yes, this kills them and the mites. Roll the bees in the alcohol wash for a few moments, then dump the liquid back into the original pan. Count the mites. A half cup is about 300 bees. One mite/300 bees is the lowest level acceptable without treating. Obviously, this hive has more mites than it should and treatment is necessary.

Oxalic Acid

The common name for OA is wood bleach.

Oxalic Acid is the latest ‘silver bullet’, but there are some conditions you need to be aware of if you are going to apply this chemical to your hives. First and foremost you are killing only the “phoretic” mites and none of the ones already under the capped brood. Phoretic refers to the mites clinging to the adult bees and these can easily be transferred from one bee to another and even from one hive to another one by bees drifting throughout the beeyard.

Drones are notorious drifters and the guard bees readily accept them as they pose no threat to the colony.

To use the Oxalic Acid sublimation (vaporization) process you need a 12 Volt ‘wand’ that is available from several sources and companies. A ‘wand’ is attached to a 12 Volt car battery and becomes heated to 375°F.

The tip of the wand (you insert into a hive) has a cup that you’ve placed one gram of Oxalic Acid powder for each deep brood box you are treating.

Then you insert the wand into the hive and finally hook it to a battery. The exact time for the OA to sublimate is 2.5 minutes. Then you must disconnect it from the battery and wait about 10 minutes for it to be removed.

This method kills about 95% of the phoretic mites so we repeat it after 15 to 20 days, but not too often as too much can harm the queen and drones along with the workers. Used properly this is an excellent tool and method to keep your mite count down.

I have read where if you have an eight to 10 mite count per hundred bees its probably too late to save the colony, but some treatment is better than nothing – I hope.

Each wand sold comes with a one gram spoon to measure the powder.

My favorite OA wand, I have two different models, is the one from the Kelley Beekeeping Co. as it has a timer in the handle and you can load the cup with the powder, insert it into the hive, while it is hooked up, and then tum on the switch which will rapidly flash a light and then shut itself off after the 2.5 minute interval. The light then continues to flash at a slower rate for a few minutes while the OA cup cools. When it stops its OK to remove the wand and treat the next hive.

The other models and brands must be disconnected from the battery as soon as the 2. 5 interval is reached or they will continue to get hotter also they cannot be hooked up until everything is in place.

Now pay attention! Buying a face respirator with filters is a must. Breathing vaporized OA can be very harmful and if you ever get a whiff (voice of experience here) of it you will be more careful in the future. Also wear eye protection goggles.

A pair of nitrile gloves is also recommended.

As with any mite treatment you must not have any honey supers on the hive. Temporarily remove them and then replace them when you are through killing mites.

The Oxalic Acid Dribble Method

Another method using OA is the dribble/drizzle method. Brushy Mountain Bee Farm has an inexpensive kit with the needed syringe and some, approved by the FDA for use in beehives OA powder. (Ed. Note, 2024: Brushy Mountain is no longer in business.)

The formula for using the dribble method is to mix 35 grams of OA granules into a 1 liter 1:1 sugar syrup solution. A liter is pretty close to a quart so this should work as a measuring device. And 1/4th teaspoon is 1 gram.

This method gives about a 55% kill rate. But don’t repeat this method more than every two weeks. Waiting 16 days is a better time frame or even three weeks.

The Insect Fogger Method

Now for another device and method for treating Varroa is to use an “insect fogger”. From my reading there are two formulas to use in one of these devices. I am told the Burgess and Cutter models are good ones. One formula is 40 grams of OA mixed into 100 ml of grain alcohol. Try not to get a whiff of this one when using a fogger. Its not too strong, but you’ll know it if you inhale any of this fog. From what I’ve seen on the Internet you just puff two to three times into the entrance and you’re done.

Remember the old saying: “if one pound is good two pounds must be better.” Forget this, it never applies to mite treatments of any kind. This idea is a good way to wipe out a colony in a hurry.

Remember throughout this article no matter what method you use only the phoretic mites are killed.

There is another formula to use in an insect fogger. It consists of one pint of food grade mineral oil to which four teaspoons of wintergreen oil has been added. Use the same procedure as for OA and alcohol.

I have not tried this one yet. You can find insect foggers at garden supply stores along with Lowe’s and Home Depot.

Foggers use a small metal propane bottle to operate them. You light the coil area at the front of the device. Use a barbeque grill wand lighter that works well.

Now for a couple more ways and items to treat Varroa.

There are so many ways to control Varroa now that I will mention a couple more. It depends on your wallet as to whether or not these appeal to you. I see a rather costly OA device advertised by Blue Sky Bee Supply that is claimed to treat a hive in 15 seconds. It requires a 120 Volt power supply to operate.

Now for a really different gadget that also uses 120 Volt power, claims to not only kill Varroa, but SHB. Not cheap, but you get what you pay for. Its developed by Bee Hive Thermal Industries.

The gadget I’m waiting for is a model drone with something it carries that can remotely be dispensed as I fly it over my beeyard.

A final mention of the line of defense against Varroa is to purchase VSH queens. Along with proper hive treatments they are well worth their cost.

Also the better times of year to treat mites is when there is little or no brood. Late Fall and late Winter.