1 FORMIC ACID FUMIGATOR FOR CONTROLLING HONEY BEE MITES IN BEE HIVES James W. Amrine Jr. 1 and Robert Noel 2 1. Division of Plant and Soil Sciences, G-168 Agricultural Sciences Buildinng, West Virginia University, P.O. Box 6108, Morgantown, WV USA 2. Fort Hill High School, 108 Blackiston Avenue. Cumberland, MD 21502, USA ABSTRACT - The 50% formic acid fumigator (FAF) for varroa mite control was developed as part of a SARE grant (1999 to 2001). The fumigator was evaluated for five years on 123 colonies in five bee yards in Connecticut, Maryland and West Virginia. Treatments eliminated all mites on adult bees and 90 to 95% of mites in sealed brood cells. Very few brood or new young adult bees were injured by the treatment. The fumigator is a simple design and the overall cost of treatment is about $1.00 per hive or less. The 50% FAF was less toxic to bees compared to other treatments using 65%. 80% or 90 % formic acid (FA). The fumigator was applied for hours, when ambient temperatures were between C. In the USA, one treatment in mid- August to mid-september was effective and usually all that was required each year. The 50% FAF used with other essential oil treatments including salt-grease patties with wintergreen, feeding 1:1 syrup with Honey-B-Healthy7 (spearmint and lemongrass essential oils), and use of screened bottom boards together provide a synergistic effect to keep mite numbers at a relatively low level, as part of an integrated pest management (IPM) system. Key Words: Formic Acid Fumigator, Varroa destructor, Acarapis woodi, essential oils, salt grease patties, screened bottom boards, Apis mellifera, Honey Bee, Honey-B-Healthy7, IPM. INTRODUCTION The varroa mite, Varroa destructor (Anderson and Trueman, 2000)(Mesostigmata: Varroidae) and the tracheal mite, Acarapis woodi (Rennie, 1921) (Prostigmata: Tarsonemidae), are the most damaging pests of the western honey bee, Apis mellifera L. (Hymenoptera: Apidae) in the world today. Since their introduction to North America in 1984 (tracheal mite) and 1987 (varroa mite), virtually all wild colonies have been eliminated, and many beekeepers, both hobbyists and professionals, have abandoned the profession. Those who remain have the hard responsibility for maintaining healthy bee colonies for pollination of crops and for the general welfare of the environment. Organic acids and essential oils now play a bigger roll in integrated pest management of parasitic mites and pathogens of honey bees, because of development of resistant mites and pathogens. The Varroa mite has become resistant to synthetic acaricides (Pettis 2004). We developed our four-fold treatment protocol (Amrine et al. 1996; Noel and Amrine, 1996) of: (1) screened bottom boards, (2) wintergreen/salt grease patties (Sammataro et al., 1996; Sanford, 1995), (3) feeding essential oil concentrate, Honey-B-Healthy7 (HBH) (Noel 2006), and (4) the 50% formic acid fumigator (Amrine & Noel 2001), to reduce and control honey bee mites using essentially natural ingredients. Five years of using the improved version of the formic acid fumigator showed that only one or two, 24 hr treatments in mid-august to mid-september (middle Atlantic States Climate) controlled both Varroa destructor and the less destructive tracheal mite, Acarapis woodi. For a full description of the other three protocols, please see our websites:
2 and Abbreviations and acronyms used in this report: C - Centigrade, cm - centimeter, CT - Connecticut, F - Fahrenheit, FA formic acid, FAF, formic acid fumigator, FA-HBH - formic acid-honey-b-healthy7, FL - Florida, HBH - Honey-B-Healthy7, MD - Maryland, PMS - parasitic mite syndrom, Qt - quart, WV - West Virginia, WVU - West Virginia University, - inch. MATERIALS AND METHODS Screened bottom boards (using 1/8" (0.375 cm) hardware cloth) for varroa mite control (Horn, 1987, Pettis & Shimanuki 1999) were used on all of our colonies. For our trials, we made an opening in the back of the bottom board, below the screen, for inserting home-made detector boards [12 1/4" x 16 7/8" (31.15x.9 cm) white demonstration board, coated with petroleum jelly (Vaseline7)] which could be replaced with a sheet of masonite for fumigation. Screened bottom boards take advantage of the natural, 10-20% mite fall that occurs throughout the year. Without vaseline, the mites will crawl back up onto the bees. The 50% formic acid fumigator, FAF, (Figs. 1-6) has two parts: an inner fumigator frame and an outer supporting frame. The outer surface has the same dimensions as a Langstroth honey super or 18" x 16 3" (45.72 x cm). The inner fumigator frame (Fig 3) is 17 long by 12 wide (44.45 x cm), made with x (1.9 x 2.22 cm) wood molding (see details in Figs. 4-5). The upper surface is covered with 1) standard aluminum or plastic window screen to protect the absorbent pad from the bees on the underside, 2) an absorbent pad (non-woven undergarment, Kendall bed pads, available from hospital supply stores or drugstores) with the absorbent surface down, and 3) a sheet of aluminum >flashing= (available from home improvement stores) as a top cover, screwed into place with 4 screws, overlapping the two sides of the fumigator frame by 2A (1.27 cm). This inner fumigator frame is nailed (from the ends) into a 1 x (4.45 x 1.9 cm) outer supporting frame, with the same outer dimensions as a Langstroth honey super (see above) forming two (0.9 cm) beeways on each side, with the top, flashing surface of the inner fumigator recessed 3/8" (0.9 cm) below the top surface, and with the bottom of the inner fumigator frame about (0.79 cm) above the bottom margin. This construction provides an important air cavity, Athe activation (Fig. 6), 1 deep x 12 x (3.175 x x cm), below the absorbent surface and just above the brood frames. In American style hives, the tops of the brood frames are recessed about 3/16" (0.476 cm) below the super margin, and allowance for this additional space will have to be made in British- or European-style hives. Application - Before treatment, we taped over all holes, openings, etc., and we used a solid bottom board, or sealed the bottom with an aluminum, plastic or masonite sheet. The entrance was reduced to a small central opening 7/8" (.95cm) x 3.5" ( 8.9 cm) (Fig. 7). At time of application (see below) we poured ozs. ( ml) of 50% formic acid (depending on the size and number of the brood chamber(s)), mixed with 10-20% (0.5 to 0.67 ozs or 15 to 20 ml) of Honey-B-Healthy7 (mixed at time of application 1 ) onto the pad and placed the fumigator on top of the upper brood chamber, with the absorbent material down. The
3 amount of formic acid mix used depended on the number and depth of the brood chambers; eg., we used 2.9 ozs (85 ml) for a single deep chamber, 3.2 ozs (90 ml) for double Illinois chambers or a deep + shallow, 3.21 ozs (95 ml), and for double deep chambers (3.38 ozs or 100 ml), etc. Fumigation is done when the ambient temperature is between C (60-85 F). The fumigator is placed on the hive at about 12:00-18:00, and taken off at about 12 noon the next day (18-24 hrs. exposure). We kept detector boards on the hives for days in order to sample mite drop during one capped brood cycle (Fig. 8D, Fig. 9). Summary of Application: 1. Ambient Temperature should be 60 to 90 F ( C). 2. Apply treatment between 13:00 & 18:00 (1-6 PM), ideally mid-august to mid-september. 3. Manage all brood frames in one or two brood chambers. 4. Thoroughly mix 85 ml (2.9 oz) of 50% FA solution with 15 ml (1/2 oz) HB; pour onto absorbent pad in fumigator. Place above upper brood chamber. 5. Tape all openings shut; if using screened bottom board, use solid Bottom Board or cover the screen with masonite, plastic or aluminum sheet. 6. Reduce entrance to x (7.5 x 1cm) at center. 7. Remove fumigator the next day between 12:00 & 18:00 (noon and 6 PM). In most cases, only one treatment is needed per season. We often go two seasons between treatments, depending on # of infested brood cells (and # of incoming mites from dying and/or wild colonies). Results After applying the FAF, the bees quickly began to fan the air through the brood nest and out of the small bottom entrance; you could easily feel the air and smell the formic acid coming out of the central entrance. During the treatments, average temperatures were F ( C) between the full brood frames, F ( C) just below the fumigator at the center of the hive, and the air exiting the entrance was nearly always 90 F (32.2 C). Temperatures were lower in the weaker colonies with just a few frames of brood. We had excellent mite kill on most hives in all of our preliminary trials (Table 1), including mites inside sealed brood cells. Because of the addition of HBH, we saw very little interruption of queen performance, and no balled queens in the WVU trial. In August, 2000 we conducted similar trials with formic acid only (no HBH), at the same concentration and amount, and lost queens in 6 out of 24 (25%) colonies (Connecticut). The Cumberland, MD, preliminary trial (41 colonies), at the same time and same doses of FA, but with HBH, had two queen losses or 4.3% loss, which may have been due to failing queens. The WVU trial of 82 colonies in September 2000, using the same doses of FA, but with HBH, resulted in no loss of queens. In 2001, in Cumberland, MD, three queens in 46 (5%) FA-HBH treated colonies were lost. Another trial in Cumberland at the same time, of 31 colonies using synthetic acaricides (Apistan & CheckMite) showed a 6% queen loss (no HBH). We have used our 50% formic acid fumigator at WVU and Cumberland, MD, for the past five years with the same, consistent results. In addition to adding the HBH to the formic acid mix, spraying the bees and brood area with 1:1 sugar syrup with 20 ml of HBH/Qt (0.95 l) helps to prevent queen loss.
4 Queen losses were reduced from 25% to about 5% or less with some trials showing 0% losses, while obtaining a 90-95% kill of Varroa on the bees and in the cells in treatments lasting less than twenty-four hours. Some open brood, and hatching young bee losses could not be totally eliminated. This minimal loss of a few hundred bees at most had no detrimental effect on colony strength (40,000-60,000). The treatments stopped varroasis in thousands of brood cells and allowed brood to hatch as healthy adults, free of deformities and disease. Large numbers of clean, healthy brood are needed for a colony to successfully overwinter. The potential loss of a handful of bees is minimal when compared to the thousands of bees saved by the treatment. Table 1. Results of 50% FAF-HBH treatment of bee hives at WVU Horticulture Farm, 18 Sep 2000; numbers of dead VM on sticky cards. Hives were maintained on two Illinois-style brood chambers, with 7 frames of brood in each hive. HFH: Hort Farm Homestead; bees purchased from Weaver Apiaries, Navasota, TX, May RNH-1: Robert Noel hive treated at the same time. All had been treated with 4 weeks exposure to low acid by wicks into brood chamber from reservoir below hive containing 40% FA and 10% acetic acid (had no effect on VM). We estimated an 80% reduction in VM populations. Hive # 24 hrs +3d HFH HFH HFH HFH HFH HFH HFH HFH RNH Avg Discussion By using a lower concentration of formic acid, approximately 44% after HBH is added, we have reduced the chance of injury to bees. This new, improved 50% Formic Acid Fumigator has inreased the efficiency of formic acid in the following ways: 1) A recessed air space is provided just above the upper brood chamber within the fumigator. Heated air from the brood rises into this enclosed space which has a controlled 92 F (33.3 C) temperature. We call this space the Aactivation (Fig. 6.) 2) The upper surface of this space has an absorbent material saturated with a 44.1% FA-HBH mix, overlying the entire brood area. The FA is much heavier than air (specific gravity of 1.11) sinks to the bottom board and does not rise. This is probably why so many investigators had variable results when placing small pads of FA on the bottom board, in the back corner of
5 colonies, in modified frames placed between brood cells, or in small pads on top of the brood supers, but with no controlled heated or evaporation space and with a fully open entrance. Placement of the FA-HBH mix about 1.25" (3.175 cm) above the upper brood frames is critical for the performance of this fumigator. 3) By reducing the entrance to 3/8" x 3.5" (0.95cm x 8.9 cm)(fig. 7), and by having only two 3/8" (0.9 cm)bee ways on the sides of the fumigator (Fig. 3), allows the FA-HBH mix to saturate the hive atmosphere which then penetrates all capped brood cells, killing 90-95%+ of the mites in most colonies in less than 24 hours. Dead mites can be found in brood cells during the next days, and these accumulate in dense bands on the detector board during this time. (Fig. 8B,C). 4) The upper aluminum sheet prevents the warm air from being lost to upper supers (boxes of frames for honey storage above brood chambers) (Fig. 2). Thus, warm air rises from the brood and activates the FA-HBH in the absorbent pad causing evaporation. The pad can hold 150 ml of solution without dripping. The bees respond with a roar of fanning, and the FA-HBH saturated air circulates throughout the brood space and eventually exits the small entrance opening. The circulating air is warm (90 F, 32.2 C) when it exits; the FA penetrates capped cells, killing mites inside, but not the brood. Within 24 hrs, virtually all of the FA has evaporated and the fumigator can be removed. The more brood frames, the better the performance of the fumigator. We feed HBH to the bees in August to stimulate brood production prior to fumigation with the FA. The detector board should be left on for 13 days (14 days for drones) to get an estimate of the mite population and mortality. This period corresponds to the number of days required for one cycle of capped brood to complete development and exit cells. As bees exit the cells, dead mites and debris fall between the frames, through the screened bottom, and onto the detector board below. Some colonies produced counts exceeding 3,000 mites on a single detector board in 13 days. We have 426 boards (Fig. 8B-E) taken from as many treatments, and it is very satisfying to see the 1000's of dead mites in the petrolatum. For most hives, one treatment usually places the colonies far below injury level for several months (fewer than 5 of 100 examined drone cells infested). Occasionally, a second treatment may be needed about two weeks after the first. Honey-B-Healthy7 and Queen Preservation - Honey-B-Healthy7 is a mixture of spearmint and lemongrass essential oils with water, lecithin and a trace of sodium laurel sulfate to stabilize the product. It has a shelf-life of several years. It is formulated so that one teaspoon (5 ml) of HBH delivers 0.5 ml of spearmint oil and 0.5 ml of lemongrass oil to the target solution, which is usually a quart of 1:1 sugar: water syrup. We compared many essential oils in treatments of colonies with parasitic mite syndrome (PMS) in 1995 and 1996; we found that wintergreen and spearmint were excellent at reducing the PMS and allowing colonies to produce normal healthy bees. Spearmint always gave superior results. However, honey bees are not attracted to spearmint oil syrup; they may take a week to consume the spearmint syrup. Bob Noel experimented with many additives to try to get the bees to feed on spearmint-syrup; he met with success with lemongrass oil. The combination was excellent and the bees took it rapidly;
6 we timed a number of colonies that were eager to forage, and they often removed a single quart in 4 hours. In cooler weather, or when the bees do not need to forage, the syrup lasts longer. Essential oil components in Honey-B-Healthy7 modify the effect of Formic Acid (FA) treatment on bee hives, such that queens are not lost. This aspect is extremely important for any beekeepers using formic acid to treat varroa mites. Fumigator evolution - In , we experimented with formic acid fumigation using shallow honey supers containing absorbent cotton on an aluminum screen attached to the bottoms; various concentrations of FA were placed on the cotton and the supers were placed on the hives. In September-October 2000, the original, thin fumigator was developed which was equivalent to just the inner frame described above, our 24-hour fumigation technique worked extremely well for us in 60-70% of the hives treated. In 2001 we developed the present fumigator with the larger above brood space and increased the efficacy to about 90% of colonies treated. The present design has not changed since Formic Acid Handling and Storage - Anyone repeating these treatments should temporarily remove honey supers, wear rubber gloves, use eye protection and have water available; do not inhale fumes (formic acid will enter the blood from the lungs and can be harmful to the liver). The 50% formic acid was mixed ahead of time; it can be stored indefinitely prior to use; but do not add the HBH until time of application. We always mixed the formic acid and HBH in an open, outside area or in a fume hood, and we used a lowcost hydrometer ($5 at to obtain exactly 50% FA (sp. grav. = 1.110). The hydrometer was needed because we found considerable variation in strength of formic acid in containers that we purchased; some were off as much as 30%. This may be one reason that published reports gave variable results for the use of formic acid. Beekeepers must also be aware that formic acid obtained from some commercial sources may contain heavy metal contaminants; these may be harmful to the bees, to humans and to the environment. Always inquire about the possibility of heavy metal contaminants. Keep the formic acid in a tightly sealed container and read the safety label and the Material Safety Data Sheet (MSDS 2006). Store it in a cool, dry ventilated area away from sources of heat or ignition. Protect against physical damage. Store away from direct sunlight. It is strongly corrosive and should be kept in containers made of 316 stainless steel, glass, ceramic or similar corrosion-resistant materials. Containers of formic acid may be dangerous when empty since they may have product residues; always rinse empty containers three times. Obsereve all warnings and precautions listed for formic acid (MSDS, 2006). Cost - Formic acid is relatively cheap. Our supplier in Roanoke VA (Chemicals & Solvents, Inc., 1140 Industry Ave., SE, Roanoke, VA; phone: ) sells FA in five gallon containers for $51.67 (March 2006), which can be stored indefinitely. Purchased FA can vary from 90% to 98% FA; when diluted to 50%, 5 gallons of FA would make about 9.7 gallons of mix. Using it at 90 ml per hive, five gallons of FA would make up about 408 treatments. On average, the cost of treating one hive is about US $1.00 or less after figuring in the cost of the sugar syrup and the Honey-B-Healthy7. Negative aspects of using formic acid - It is toxic and can cause skin and liver problems if the operater is careless, especially with the concentrated acids (MSDS, 2006). However, the
7 advantages and simplicity of using FA certainly outweigh the disadvantages. It is found naturally in honey in small amounts (Bogdanof et al., 2002). Beekeepers should remove honey supers during treatments; they can be replaced the next day after the fumigator is removed. There is occasional, minor brood injury and we noticed a small kill of young emerging workers and emerging drones in 6 treatments conducted in April, 2005: about bees per populous colony. However, it is effective on tracheal mites as well as varroa mites, and no mite resistance has so far been reported for Formic Acid treatments. Why does the formic acid fumigator work? - The strong hydrogen bonds in formic acid cause the vapors to act more like liquids than like gasses (Laffitte, 2006). Concentrated solutions of formic acid, 60%, 65%, 80%, 85% and 90% (used in many different formic acid treatments in Europe and North America (Anonymous, 2002; Becker, 1994; Imdorf et al., 1999; Chapleau, 2003)), act like liquids, not vapors when they evaporate. The dense vapors flow directly to the bottom of the hive, and out onto the ground, where they kill grasses and weeds. When mixed with water at 50%, the resultant vapor acts more like a gas, does not sink as quickly, and has a longer hang time in the brood nest. But it is still a fluid-like vapor that has the ability ot penetrate the brood cappings and to kill the varrroa mites within the cells. Why does it kill varroa mites and tracheal mites but not honey bees? Mites have cuticles more permeable to FA; formic acid directly enters their hemolymph, acidifying the acarine brood, killing the mites. Honey bees have a cement layer covering the epicuticle which repels many external chemicals like FA. This cement layer is thinner and less effective in some larvae and newly emerged adult bees which is why we see some mortality ( /colony) of small or recently eclosed larvae and of newly eclosed workers and drones. The vast majority of the bees are not harmed by 50% FA fumigation. CONCLUSIONS This fumigator is inexpensive, simple to use, and very effective if used on colonies with many brood frames and when ambient temperatures are between F (18-30 C). We believe that State Departments of Agriculture and (USA) should make an exemption to apiary laws to allow use of the 50% FAF to treat colonies infested with Varroa mites. We envision a central beekeeper=s cooperative, regulated or licensed by the state, who purchases the concentrated formic acid in 5 gallon or 15 gallon containers, diluting it accurately to 50% FA, and providing it to beekeepers in small sturdy containers for treatment of their bees. Another effective way to regulate the treatments would be for Beekeeping Clubs and Associations to function as a cooperative as described above. They would buy the concentrated FA, dilute it accurately to 50%, and sell small containers of the solution to beekeepers needing the treatment. They could even manufacture 10 or 20 of the fumigators and have them on hand to loan to the beekeepers. Details of the construction of the fumigator are provided so that it can be made for a few dollars, within a few hours, by anyone familiar with woodworking techniques. We want to make this fumigator public knowledge in order to benefit beekeepers and the honey bee. The basic fumigator and its concepts were presented in our research report to SARE (Amrine & Noel 2001), and thus deem its design to be public property. We have no intention of trying to obtain a patent on this useful device. Infringement of this intellectual copyright property is prohibited without proper acknowledgement given to the inventors of the device.
8 The once simple hobby of beekeeping is rapidly becoming the science of beekeeping with knowledgable beekeepers who can find and identify pests, and know when and how to apply various treatments to control them. Because varroa mite is now resistant to synthetic acaricides, a disciplined, year-round treatment protocol will have to be followed, combining the use of organic acids and essential oils, or similar techniques, to control parasitic mites and pathogens in honey bees. Our united control efforts will vary by region, with adjustments made for the various climatic conditions and beekeeping practices. Finally, mites may not develop resistance to essential oils and formic acid as with synthetic acaricides. Formic acid has been used in Europe for about 25 years with no known report of mite resistance. Caution - When working with formic acid, wear gloves, eye protectors and have plenty of water available for flushing if needed. Remove honey supers before fumigation. Be sure to have good ventilation or work out of doors. Do not allow the FA to become excessively warm (eg, sitting in the sun) as this will shock the bees. We encourage beekeepers to experiment with this fumigator and with various formic acid formulations, in order to determine its efficacy and limitations. Please be careful and only work with a few colonies at a time until we better understand its function under various conditions. Planned Future Work - We intend to conduct trials in the future using the 50% FAF in more tropical conditions, hopefully in FL, and if funding becomes available, in some other states. ACKNOWLEDGMENTS This research would not have been possible without a grant from SARE, USDA, and support by the West Virginia University Experiment Station. Robert Noel s late sister, Marlene Noel, gave him the idea, and valuable inspiration for using essential oils to improve the health of the honey bee. Our colleague, Tony Delia, in West Redding Connecticut, provided much of the inspiration for developing this formic acid fumigator. One of our greatest supporters for our mite research over the years has been Vikram Prasad, M.D., West Bloomfield, Michigan. Many beekeeper friends from throughout the US and Canada, and elsewhere have tried our fumigator and other methods in our protocol and have given us positive results and many useful suggestions. Last, but not least, we owe a great debt to our families for supporting us and putting up with out frequent absences throughout the past 11 years. To all, we give our deepest thanks. Published with the approval of the Director of the West Virginia Agricultural and Forestry Experiment Station as Scientific Article Number This research was supported in part with funds under the Hatch Act. FIGURE CAPTIONS Figs Details of the 50% formic acid fumigator (FAF). - 1, FAF standing on edge; 2. Top of FAF (Outside dimensions: 18" x 161/4" (45.72 x cm)); 3. Bottom view of FAF; 4. Side view details of FAF; 5. End view details of FAF; 6. The activation cavity
9 formed by the fumigator; evaporation of the 50% FA-HBH mixture is driven by heat from the brood. Figs. 7, 8 - Details and results of formic acid fumigator (FAF) - 7. Entrance cleat reduced to 3.5" x 3/8" (8.9 x 0.95 cm) at the center; 8. Results of using the 50% FAF; A-C. Showing initial treatment on 12 September 2000; D, E: Showing second treatment (13 days later) on 28 September (A. Test hive #5, MD, 12 September honey left on to detect FA contamination; B. Detector Board, ca. 500 dead mites. C. Close-up of B, 49 dead mites; D. Same hive, 30 September 2000; E. Close-up of D showing 8 dead mites). Fig. 9. Varroa mite development in drone and worker cells, showing period of capped cells (modified from Martin (1997)). Figs Demonstration of the 50% formic acid fumigator, 3-4 Apr Monday, 3 April, 9:16 am, Church Bee Yard, Alachua Co., Florida. Arrow indicates the fumigator. This is a one and a half story hive with just over 3 frames of brood. Fumigator was applied at 9:15 with 85 ml 50% FA and 15 ml HBH. Clear sunny day, 88 F; in shade at 12: Same hive, 4 April 2006, 8:33 am (fumigator removed after 23 h, 18 m); some of the nearly 200 worker and drone larvae and pupae removed from capped brood cells; a total of 170 varroa mites were removed from worker and drone cells; all were dead except two in one capped drone brood cell. An additional 69 mites were dead on the bottom board, which were the mites on adult bees. Three, lively, small hive beetles (Aethina tumida Murray)(Coleoptera: Nitidulidae) emerged from the hive and brood frames, unscathed by the formic acid treatment. This was a demonstration conducted by Jim Amrine, David Webb, FL beekeeper, and FL Apiary Inspector. A week later, the apiary inspector reported that this colony was okay, bee losses were minimal, and that the queen was present and laying eggs. REFERENCES Amrine, J. W. Jr. and R. Noel Controlling Honey Bee Mites with Essential Oils, Final Report to SARE (Sustainable Agriculture Research and Extension, USDA), PROJECT NUMBER: 98LNE (usda 98-coop ), 28 Dec pp. Amrine, J. W., Jr., Stasny, T. A., Skidmore, R New mite controls investigated. Amer. Bee J. 136(9): Amrine, J. W. Jr., Noel, R Controlling Honey Bee Mites with Essential Oils. Final Report to SARE (Sustainable Agriculture Research and Extension, USDA), Project Number 98LNE (USDA 98-COOP ), 28 Dec pp. Anonymous Guideline on use of formic acid for Varroa control. Ministry of Agriculture and Forestry Biosecurity Authority, Wellington, NZ. 11pp. df. Accessed 23 Mar 2006.
10 Becker B Ameisensäure gleichmässig verdunsten lassen, Deutsches Bienen J. (7): Clay, H Oxytetracycline - Let's Not Lose It. Hivelights 15(3): Bogdanov, W., J.-D. Charriere, A. Imdorf, V. Kilchenmann and P. Fluri Determination of residues in honey after treatments with formic and oxalic acids under field conditions. Apidologie 33: Chapleau, J.-P The Flash application method for formic acid. Http//:www.reineschpleau.wdl.net/articles/flash.en.html. Accessed 10 April Horn, H (Observations on the overwintering of honey bee colonies in hives with open and solid floorboards.) Allgemeine Deutsche Imkerzeitung 21(11): Imdorf, A. J.-D. Charrière and P.Rosenkranz Varroa control with Formic Acid. Swiss Apicultural Institut, FAM, Liebefeld, CH-3003 Bern, and University of Hohenheim, State Institute of Apiculture, D Stuttgart. Control with Formic Acid. Accessed 23 Mar Laffitte, M Formic Acid. Accessed 10 April Martin, S. J, Varroa jacobsoni population biology research in the UK. American Bee J. 137(5): MSDS Number: F /30/05: Accessed 10 April Noel, R Feeding Essential Oils to help maintain healthy colonies. Accessed 24 Mar Noel, R. and J. W. Amrine, Jr More on essential oils for mite control. Amer. Bee J. 136(12): Pettis, J. S. and H. Shimanuki A hive modification to reduce varroa populations. Amer. Bee J. 143(6): Pettis, J. S A scientific note on Varroa destructor resistance to coumaphos in the United States. Apidologie 35(1): Rennie, J Notes on acarine disease. Bee World 2: Sammataro, D., S. Cobey, B.H. Smith & G.R. Needham Vegetable-Shortening Patties Control Tracheal Mites (Acari: Tarsonemidae) in Honey Bees (Hymenoptera: Apidae). Proceedings IX International Congress of Acarology, 1994, Columbus, OH.
11 Sanford, T Discussion of beekeepers adopting grease patty technology for tracheal mite control, Apis, December 1995.