ADDITIONAL RESULTS OF RESEARCH
Varroa Mite Control, 1996
http://www.wvu.edu/~agexten/varroa2.htm

(September 17, 1996). We will update this web page about monthly as we learn more from our experiments and as we receive results from other beekeepers. This page is designed for beekeepers. (For those needing help with terminology, please see Graham, J. 1992. The Hive and the Honey Bee, Dadant & Sons, Hamilton IL, 1324 pp.)

Eradication possible? We believe that during the late fall and early winter the varroa mite is very susceptible to control by essential oils. By treating hives with the grease patties and syrups containing wintergreen, tea tree or patchouli oils, and making sure the treatments are near the cluster, then the varroa mites will have no place to hide and all can be killed. (No brood cells will be available as shelters.) Because most of the country has lost feral colonies, and only careful beekeepers now have bees, a concerted effort by all beekeepers at this time may achieve eradication of the varroa mite. We are not as sure about tracheal mite--(there are so few around this area that we can not find a sufficient infestation to test), but it, too, is probably susceptible to winter treatment with grease patties containing essential oils. This critical opportunity in beekeeping may not come around again for some time to come: our scenario is that with the feral colonies gone, many new colonies will be established in the next few years which will have light infestations of mites; swarms will issue from these and begin to reestablish a feral population--containing at first a few varroa mites. In a few seasons the mites will increase and another epidemic of fatal varroa mite + PMS will occur. As the new feral colonies increase, it will become impossible to find them and to eradicate their varroa mites. That is why now is such a special opportunity to attack this pest.

We learned recently that EPA exempted certain active ingredients from the requirements of FIFRA including some essential oils; this information can be found in the Federal Register, Vol. 61, No. 45:8876-8879, Weds., Mar. 6, 1996 ("Exemption of certain pesticide substances"); materials listed include cinnamon oil, citronella oil, lemongrass oil, mint and mint oil [eg., Patchouli oil], peppermint oil, etc. EPA further stated that the inert substances in Fed. Reg. Vol. 61, No. 45 can be added to the active ingredients listed in Fed. Reg. Vol. 59, No. 187:49400-49401, Weds., Sep 28, 1994 ("Inert ingredients in Pesticide Products"), including cloves, mineral oil, parafin wax, wintergreen oil, etc. The label for exempted products must list the name and percentage (by weight) of each active ingredient and the name of each inert ingredient, and must not contain any false or misleading statements (40 CFR Art. 156.10, 1 July 1994). Many states require some form of state labeling such as "Attention: this product is a pesticide which is exempt from federal safety testing requirements. State registration does not imply safety of efficacy. User assumes full liability of use." Contact your state pesticide office for their requirements.

SUMMARY OF EXPERIMENTAL TREATMENTS (REVISED):

1). Syrup: 25 drops (1 cc) of wintergreen or spearmint added to two cups (about one pound or 453.6 grams) of sugar in a quart jar (0.95 liter); hot water added to fill jar. Be sure to add the oil to the granulated sugar then add the very warm water (not too hot or else the oils will evaporate). Feed the bees as much syrup as they will take. We have had good results with wintergreen, spearmint, and peppermint oils.

2). Grease patties: are made with four cups of granulated sugar, two cups of shortening and one of the following: 21 cc of wintergreen oil or 21 cc of patchouli oil or 21 cc or tea tree oil or 11.5 cc of each of two oils (eg., wintergreen + patchouli). (This rate is 1/4 oz. of essential oils per pound of sugar and grease). The components are thoroughly mixed (wear gloves or use a large spoon, as wintergreen oil in such concentrations may be toxic; patchouli oil is not toxic). The mixture is then made up into 4 ounce patties (like a small, 3.5" hamburger) which are divided and placed on top of each brood box (about one half pound or 8 ozs. of grease patties per hive; one batch treats 5.8 hives). We plan to make patties this fall that also contain terramycin (TM25) to determine whether medications can be combined for both mites and foul brood.

3). Tracking strips: are made by cutting sheets or pieces of 1/8 in. plexiglass into strips 3" wide by 14" long (7.5 cm by 35.5 cm ), and used as a base for holding a treated slurry containing essential oil. The slurry is made as follows: 17.5 ozs. (2 and 1/5 cups) of canola oil are mixed with 6.5 ozs. (slightly more than 4/5 cup) of melted beeswax, stirred and set on a hot plate. To this liquid add 24 cc's of wintergreen oil (or 24 cc's of patchouli oil or 12 cc's of each ). Stir well and pour into three 8 oz. plastic cups. When cooled, the slurry has a shoe-polish or salve-like consistency. Then, 2 to 3 teaspoons of the slurry are applied to the tracking strip which is placed lengthwise just inside the front entrance of each colony. The bees must track through this slurry when they enter or exit the hive; they then clean off the slurry by eating it and feeding it to each other. Treatments are repeated after 5 days: the old slurry, dead mites and dead, deformed bees are scraped off and new slurry added. Plexiglass is used for tracking strips because it has a very smooth finish allowing an even coverage and it is too hard for the bees to chew up or remove; masonite or other similar material could be used just as well.

4). Paper inserts at top of hive: For control of varroa mite on displaced nurse bees (see below). Use 2 cups of canola oil containing 11 cc's of wintergreen; put some in a honey bear (as a squeeze bottle) and apply 6 lines of wintergreen oil in both directions on a paper towel so that the towel is saturated. The bees chew it up and remove it in a week or so. You should replace it as needed to treat the varroa mites trying to avoid the other treatments.

Varroa Mite Assessment: You can place a sticky board on the bottom of the hive in combination with both patties and a tracking strip to obtain a good count of varroa mites within 24 to 48 hours: in our tests the essential oils killed more mites than Apistan.

We use the essential oils throughout the year, either feeding syrup (when nectar is not coming in), using patties (pretty much year around, but bees do not use the patties as much during honey flows), and using the tracking strips, which are especially useful during the honey flows. The best results came from a combination of all three treatments.

We have found in recent months:

In colonies treated with tracking strips at the entrance and grease patties over the brood chambers, we found that varroa mites were able to escape treatment: displaced nurse bees, which gather under the inner cover were used as a hiding place by the mites. We treated this group of bees and mites by putting a piece of paper towel treated with canola oil and wintergreen (8 cc wintergreen in one cup of canola) just under the inner cover. We placed the oil treatment in a honey bear (used as a squeeze bottle) and applied 6 lines of wintergreen oil in both directions on a paper towel so that the towel was saturated. The bees chewed it up and removed it within a week or so. Very few mites were found on these bees after treatment.

The tracking strips and grease patties are lethal to exposed mites, but the mites also escape the treatment by going into brood cells being capped. There were very few mites on adults in treated colonies (thus, the ether roll would have come up with 0-4 mites), but the mites were reproducing at normal levels in worker brood cells and drone cells. The few remaining drone cells had lots of mites in them (13 Sep 96). We conclude that the essential oils in tracking strips and grease patties do not enter the food chain sufficiently to impair mite development.

The colonies that were fed syrup with essential oils, in addition to using tracking strips and grease patties, were virtualy free of varroa mites, without using Apistan.

Large colonies: we also found that colonies with many supers and thus lots of space made mite control more difficult: the treatments were too diluted by the volume of space and number of bees. Therefore, we recommend getting honey supers off as soon as possible and reducing colonies to 1 or 2 brood chambers at most.

In some of our colonies, grease patties containing spearmint oil were propolized; but not those patties made with wintergreen, tea tree or patchouli oils.

Queens: A potential problem may be that queens on mating flights may have their pheromone masked or may become somewhat disoriented by essential oils. We recommend that the essential oil treatments be removed from the hives when queen rearing and mating is taking place.

Drones: We found that large numbers of drone cells provide protection to the varroa mites and are definitely the source of most breeding varroa mites. Consequently, we recommend that the amount of available drone cells be kept to a mininmum; be sure to remove and replace old comb containing lots of irregular drone cells. (See the literature for techniques using periodic drone removal to reduce varroa mites).

Note about tracheal mites: We checked Bob's colonies for tracheal mites by collecting older foragers: those that have frayed wings and a bald thorax. We removed their heads and first pair of legs and examined the tracheal trunks that are visible inside the cavity where the legs were (peel off the "collar" with forceps); infested tracheae could be seen with a hand lens and were dark spotted or uniformly dark. Results: in some control colonies (no treatments) 30% had tracheal mites; in treated colonies, 10% or less had tracheal mites. Since bees are able to drift considerable distances, we suspect that some of those in our treated colonies may have come in from other, declining feral colonies in the neighborhood (a few feral colonies still remain near Cumberland, but these should be gone soon). The older bees give a more reliable test for the presence and extent of infestation by tracheal mite. We learned that British beekeepers, up until about 1950, used a bottle of wintergreen oil (with a wick through the top) in the bottom of their hives to control acarine disease (tracheal mites). So, apparently, wintergreen (methyl salicylate) was use to control these mites. We also learned that Dr. Rennie, around 1920-1925, recommended wintergreen over the original Frow treatment of safrol­nitrobenzene­petrol as a treatment for Isle of Wight Disease (acarine disease or tracheal mites) (courtesy of Mr. Joe Hemmens, UK).

Questions or comments please contact:
James W. Amrine, Jr.
Division of Plant and Soil Sciences,
P. O. Box 6108, West Virginia University
Morgantown, WV 26505-6108 USA
Telephone: 304-293-6023
E-mail: jamrine@wvnvm.wvnet.edu

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