Associate Professor and Extension Apiculturist, NC State University
It has now been over 25 years since the introduction of varroa mites, and we are still faced with the ongoing struggle of keeping our colonies healthy from these parasites. The mounting evidence that the easy-to-use synthetic acaricides, specifically the pyrethroid fluvalinate (Apistan®) and the organophosphate coumaphos (CheckMite+®), have some major drawbacks. First, the mites are now showing resistance to these pesticides, so that they are unreliable at best of ineffective at worst. Second, these chemicals are lipophilic, meaning that they get absorbed and remain in the wax comb, which can have negative consequences on our bees. Finally, these two chemicals have been recently shown to synergize their effects, so that in concert they can be more deadly to the bees than when used alone. These and other problems have prompted the development of several alternative means of mite control, including screened bottom boards, mite-tolerant stocks, and thymol-based products such as Apilife VAR® and Apiguard®.
|Varroa mites on adult honeybee (http://agnewsarchive.tamu.edu/stories/ENTO/varroa.htm)|
Several years ago, there was an organic acid product called Mite-Away II™, the active ingredient of which was formic acid. Treating a colony with formic acid controls varroa by turning the hive into a “fumigation chamber”, where the formic acid vapors actively kill the mites. It was a ready-to-use product consisting of a fiberboard pad soaked with 250 ml of 65% food-grade formic acid inside a perforated plastic pouch. While formic acid treatment has been shown to be quite effective in the control of varroa mites, the Mite-Away II™ pads have now been removed from the shelves.
In its place, a different product has been recently granted Section 3 registration from the U.S. Environmental Protection Agency for the control of varroa mites in beehives, and thus beekeepers in North Carolina have received regulatory permission to use this new product. Mite-Away Quick Strips™ (MAQS for short) is a formic acid gel strip product that requires only one 7-day application of two strips per treatment placed on the top bars of the hive. This new product has some important pros and cons of which every beekeeper should be aware before using.
1. Can be used during the honey flow. The previous label stipulated that if treatment is conducted before a honey flow, honey cannot be harvested within two weeks after the end of treatment. The current label does not include this restriction, so that the product can be applied while honey supers are on a colony during the honey flow.
2. Claims to kill mites inside the brood cells. MAQS™ are reported to achieve “up to 95% mite kill and penetrates the capping to destroy the male mite and immature female mites as well as the phoretic female mites on the adult bees.” There are no scientific peer-reviewed results on their efficacy, however, so the basis of these numbers are the original EPA registration data.
1. Respirator is required by the label. Care must be taken by the beekeeper while applying formic acid, as it is highly corrosive and poisonous to humans. Importantly, a breathing respirator is required to apply the product. In addition, the label requires coveralls, a long-sleeved shirt, long pants, socks, shoes, protective eyewear or goggles, a veil, and beekeeping or acid-resistant gloves (latex gloves will degrade upon exposure to formic acid and therefore are not adequate). Avoid contact with skin, eyes, and clothing, as formic acid can cause skin burns or even be fatal if inhaled or swallowed.
Can easily burn brood. Formic acid vapors have been shown to kill larvae, which can be very disruptive to colony productivity. This is particularly true at temperatures above the label maximum of 93°F. Thus sufficient foresight in weather conditions and time of year is recommended to minimize the negative impact on colony brood rearing.
3. Can overwhelm small units. Small colonies (fewer than 6-10 frames of bees) can be overwhelmed by the fumes and drive the adult population out of the hive.
The current availability of Mite-Away Quick Strips™ pads is somewhat limited, thus there may be some difficulty in locating the product. A list of U.S. suppliers and additional information can be found at http://www.miteaway.com or toll-free at 866-483-2929.
“Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by North Carolina State University, North Carolina A&T State University or North Carolina Cooperative Extension nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact an agent of North Carolina Cooperative Extension.”