Vol. 33, No. 2 Internat. J. Acarol. 1

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1 Vol. 33, No. 2 Internat. J. Acarol. 1 RESULTS OF 50% FORMIC ACID FUMIGATION OF HONEY BEE HIVES [APIS MELLIFERA LIGUSTICA (HYMENOPTERA: APIDAE)] TO CONTROL VARROA MITES (ACARI: VARROIDAE) IN BROOD COMBS IN FLORIDA, U.S.A. James W. Amrine, Jr. 1, Robert C. Noel 2 and David Webb 3 1. Division of Plant and Soil Science, West Virginia University, PO Box 6108, Morgantown, WV 26506, U.S.A. ( jamrine@wvu.edu); Blackiston Avenue, Cumberland, MD 21502, U.S.A. ( rcnoel@atalanticbb.net); Elkcam Blvd., Cocoa, FL ( webbshoney@msn.com). ABSTRACT - We used the 50% formic acid fumigator to treat 51 honey bee colonies in Florida on April 2, August 16 and October 23, 2006 and January 2, 2007, to control varroa mites. Treatments consisted of 90 to 110 ml of 50% formic acid mixed with 15 ml of Honey-B-Healthy essential oil concentrate to prevent queen losses. The fumigator was applied during daylight hours to each hive, screened bottoms were covered, openings taped over, and the entrance reduced to 3/8 by 3 1/2 (0.95 cm x 8.9 cm) and removed the next day after from 17 to 23.3 hours. Average mortality of varroa mites in capped drone cells was 93% (92.8% to 98.8%) (after adjustment for Abbott s correction for control mortality). Capped drone cells in old black comb had the lowest mortalities (66% to 84%): less of the 50% formic acid vapor was able to penetrate the thicker cappings. Key words - Acari, Varroidae, varroa mites, formic acid fumigation, control, U.S.A. INTRODUCTION Varroa mites, Varroa destructor Anderson and Trueman, 2000 (Acari: Varroidae), are the most deadly parasites/pests of the honey bee, and have the potential to make the western honey bee, Apis mellifera (Apidae: Hymenoptera) extinct. The problem of varroa mites in bee hives has become very severe in the past few years because of the development of resistance in the mites to all three synthetic acaricides: fluvalinate, couma- phos and amitraz. Mite populations everywhere are increasing, virus infections are appearing and increasing and many beekeepers are having 100s or 1000s of honey bee colonies die off due to a multitude of pathogens, pests and problems, but often related to the increased numbers of varroa mites and their vectored viruses. Formic acid treatments have been used for several decades in Europe and the United States to attempt to control varroa mites. Virtually all of these methods use 65% or 80% formic acid in pads, placed in various locations in the hive (bottom, back, top or in modified frames, with or without reservoirs) and are set up as slow release formulations over several days, 21 days, 30 days, usually from pads or from gels. All of the treatments keep the hive entrance wide open during the treatment and queen loss is often quoted as a problem. In some papers, mite kill in brood cells is mentioned, but a statement is usually made that simultaneous worker bee or queen losses are unacceptable when this happens. It is not our intention to provide a review of all of the methods for using formic acid; the following papers relate to recent work in Europe and in North America (Annonymous, 2007; Bitenc and Snajder, 2003; Calderone, 2000, 2005; Eischen, 1998; Eguaras et al., 2001; Elzen et al., 2004; Goodwin and Van Eaton, 2001; Honey Bee World, 2000; Imdorf et al., 1999). Since 1995, we have been conducting research on using essential oils in sugar syrups and grease patties to strengthen bee colonies, and to use the 50% formic acid fumigator to kill varroa mites in capped drone cells (Amrine et al., 1996; Amrine and Noel, 2001; Amrine and Noel, 2006; Noel and Amrine, 1996; Noel et al., 2002a,b). In March 2006, we received a call from David Webb, commercial beekeeper in Florida, who reported many beekeepers with dying bee hives. After calling several beekeepers, he was told about our methods for reversing bee hive collapse and producing healthy bees. David s operation was down to about 300 colonies (from 475) and he could not keep them healthy; he was seriously planning to leave commercial beekeeping. He asked us to submit a grant proposal to the Florida Department of

2 2 Amrine et al Fig. 1. Apis mellifera ligustica infested with varroa mites - A (left): A honey bee colony with wintergreen grease patties applied 3 days before use of formic acid to drive varroa mites into the cells on February 18, 2007 in Cocoa, Florida; B (right): A drone showing a varroa mite with its feces (white). Fig. 2. New paper pad treatment - The stiff white pad is 8.5 x 11 inch blotter paper (AC16.085, Gusmer Enterprises, Wisconsin) supported by three drinking straws and with 90 ml (3 ounces) of 50% formic acid; the brown paper towel had 15 ml (0.5 ounce) of HBH; we covered the pads with plastic wrap or waxed paper over the brood chamber (held in place with duct tape), leaving one top bar space open at the left as a beeway to the honey. The entrance was reduced with a paper roll to 38 mm (1.5 inch) held in place with duct tape. The hive on the left was treated and the honey super replaced. The formic acid was gone by morning and bees removed everything in a few days (Near Fort Pierce, Florida, April 16, 2007).

3 Vol. 33, No. 2 Internat. J. Acarol. 3 Agriculture to treat failing bee hives and to control varroa mites. We received a grant for $50,000 to attempt to control the pests of the bee hives in Florida. Since this paper was written, there were numerous reports of major losses of beehives in 2007 throughout the USA and Europe. Some reports listed nearly 70% overall losses of honey bee hives in eastern North America (Barrionuevo, 2007; Fox News, 2007; Hayes, 2007; Hunt, 2006; Latsch, 2007; MAAREC, 2007; PSU, 2007; Teague, 2005). MATERIALS AND METHODS From April 2006 until January, 2007, we worked with several beekeepers in Florida to save declining honey bee hives. Our treatments follow a three-part protocol: (1) Feeding Honey-B-Healthy a feeding supplement containing spearmint and lemongrass essential oils, added to 1:1 sugar syrup at 10 ml of HBH per 0.91 l of syrup in order to build up colonies to produce sufficient brood so that the formic acid fumigation will work (heat from several frames of brood is required to cause the formic acid to evaporate and thus kill the varroa mites). (2) Treating colonies with wintergreen-salt grease patties on brood frames and at the entrance to drive varroa mites into cells and to improve the health of the bees. The patties contain hydrogenated vegetable oil, granulated sugar, salt, honey and wintergreen oil (Amrine and Noel, 2006; Noel et al., 2002a,b; Noel, 2006) (Fig. 1A). (3) Application of the 50% formic acid fumigator for a hour treatment to kill varroa mites in brood cells and adult bees (Amrine and Noel, 2006). Honey bees - David Webb s bees were three banded Italians (Apis mellifera ligustica, Hymenoptera: Apidae). David produced many of his own queens. Several groups of his bees were maintained separately in order to keep mite numbers high for our research. When mites became excessive in these colonies, numbers were reduced by using powdered sugar treatments (Fakhimzadeh, 2000). Prior to treatments, David selected 10 or 20 treatment colonies based on numbers of mites on sticky boards from the previous week, and based on numbers of varroa mites observed in opened drone cells. For each test David provided an additional 3 to 4 colonies in order to have replacements available in case a colony became queenless or some other adverse problem arose. Hives were arranged four per screened pallet, as single or double brood chambers (indicated in the separate treatments); pallets were positioned 10 feet apart. We followed the standard practice of many large-scale commercial beekeepers in Florida (Fig. 2). Controls - Ten control hives were selected for simultaneous treatment for each test using just HBH and water applied to the fumigator. Our experiment station statistician, Dr. George Seidel (who unfortunately passed away on 19 April 2007), conducted a Power Analysis (SAS) of our experiments doing 1000 reiterations and found that six controls would be adequate to achieve 100% power for each test of 20 colonies, and three controls would achieve 100% power for a test of 10 treatments. We used 10 controls, more than needed, in order to satisfy the power analysis requirement for tests for either 10 or 20 treatments. Treatments - Four applications of the 50% formic acid fumigator were made in 2006 and 2007 as follows: (1) Florida Department of Plant Industry Church bee yard, Alachua County, FL, on April 3, A single, one and a half story bee hive was treated with 90 ml of 50% formic acid and 15 ml of Honey-B-Healthy (HBH, a concentrate of spearmint-lemongrass essential oils to prevent queen loss) at 9:15. This was a pre-proposal demonstration of our method on a single bee hive. (2) Hope Ranch, just west of Cocoa, Florida, on August 15, Ten double colonies (two full-depth brood chambers per hive) were treated with 90 ml of 50% formic acid mixed with 15 ml of HBH, at 13:30. Control hives received 105 ml of water and 15 ml of HBH. (3) Duda Ranch, just west of Pineda, Florida, on October 23, Twenty double colonies (two full-depth brood chambers per hive) were treated with 110 ml of 50% formic acid mixed with 15 ml of HBH at 17:00. Ten control hives received 110 ml of water mixed with 15 ml of HBH. (4) Duda Ranch, just west of Pineda, Florida, on January 2, Twenty single colonies (full depth brood chambers) were treated in order to prepare colonies to meet stringent California inspection requirements for almond pollination. Colonies were treated with 90 ml of 50% formic acid mixed with 15 ml of HBH, starting at 13:40. Ten single hive controls received 90 ml of water mixed with 15 ml of HBH. One week prior to treatments, commercial (Dadant and Sons) sticky boards with screens were placed on the bottom boards of colonies; they were replaced at treatment and removed and replaced one week after treatment. Counts from these boards will be used to estimate the approximate numbers of mites killed by the treatments. Because dead mites continue to fall for days after treatment (the capped brood period), no precise estimate of mortality can be made from sticky boards. The loose design of the screens allowed honey bees to get under the screen in many instances; the presence of the small hive beetle in many hives damaged the results and removed many of the mites from the screens. Alcohol washes (Sanford, 1995) were conducted to sample varroa mites that were phoretic on adult bees; the alcohol helps to remove mites from their concealed locations under the lateral flanges of tergites II, III and IV. We used a modification of this technique as demonstrated by the Florida DPI. Alcohol washes were taken at the time of treatment, the day after treatment and 1 week after treatment. Procedure: About 300 bees (1/4 pt or 200 ml) from the brood area was made before treatment, the day after

4 4 Amrine et al Table 1. August 15, 2006 treatments west of Cocoa, Florida. Ten hives treated with 90 ml 50% formic acid + 15 ml HBH. Mite counts were made from 100 capped drone cells per hive on August 16, treatment and one week later (care was taken to avoid washing the queen). About 200 ml of ethanol was added to a covered pint mason jar containing the bees and shaken vigorously. The lid was replaced with 1/8th inch (3.18 mm) hardware cloth fitted within a ring, and the contents shaken vigorously into a white plastic container. Washings were repeated three times for each sample and the mites counted. Strength was subjective, based on the relative numbers of bees at the entrance and on the number of frames covered with bees, and was rated from 0 to 10 (10 with most bees). Proportion mortality data were arcsine square-root transformed before analysis (Fry, 1993) with ANOVA (SAS Institute, 1999). Temperatures and humidities were recorded using an ExTech 390 Precision Psychrometer at the time of treatment. This psychrometer has an elongate cylindrical 11/16" (17.46 mm) diameter probe (containing the wet bulb/ dry bulb combination) that can be inserted into the entrance of hives or into holes drilled into supers. Assay - For our assay, after removal of the fumigators, 100 capped drone cells were opened from each hive and all contents removed. Reading glasses, 2x magnification, were used to help see the mites and contents of each cell. Small artist s brushes were swabbed in each cell to remove all contents. The contents of the first 40 cells were preserved in 70% ethanol as voucher specimens. Counts of live and dead varroa mites, in all stages, were recorded; mites that showed any movement of legs or tarsi were counted as live. We sampled capped drone cells since varroa mites are more abundant in drone brood (Ellis and Baxdale, 1994; Martin, 1997). Also, Van Engelsdorp (2005), in his Table 2. August 15, 2006 treatments. Ten control hives treated with 105 ml water + 15 ml HBH. Mite counts were made on August 16, 2006, from 100 capped drone cells per hive.

5 Vol. 33, No. 2 Internat. J. Acarol. 5 Table 3. August 15, 2006 treatments West of Cocoa, Florida (August 16 and 29, 2006). Alcohol washes (mites per colony) and strengths. work on the flash fumigator showed greater mortality caused by 50% formic acid vapors in capped worker brood cells (55-64%) compared to that in capped drone cells (6-30% mortality) (his exact treatment conditions were not reported). For this reason, we report mortality in capped drone cells, except where noted. During winter months in Florida, many colonies not only tolerate the presence of drones, but keep producing drones throughout the winter (pollen and nectar are brought in year round except during severe dearth). As in any study of arthropod mortality between treated and untreated samples, Abbott s formula was applied to the results to adjust for control mortality (Anonymous, 1981). According to Ellis and Baxdale (1994) and Renz (2003), the majority of varroa mites at any given time are in brood cells, when brood is present (most of the year in Florida). RESULTS (1) April 3, Ambient temperature was 74 F (23.3 C); maximum for the day was 88 F (31.1 C), RH 57%. The fumigator was removed at 8:33 am on April 4, Table 4. October 23, 2006 treatments at Duda Ranch, Pineda, Florida. Treated 20 hives with 110 ml 50% formic acid +15 ml HBH, 15:30. Mite counts were made on October 24, 2006 from 100 capped drone cells per hive.. * * * *

6 6 Amrineetal Table 5. October 23,2006 treatments. Ten control hives were treated with 110 ml of water + 15 ml HEH. 2.67% Hive % Total Dead 0 a a Alive Mortalitv #Cells Inf. Mean :; 2.28'0 57%. The fumigator was removed at 8:33 am on April 4, 2006 (after 23 hours, 18 minutes). Two hundred mostly drone and some worker brood were removed from capped cells: 170 varroa mites were found and only 2 were alive (in one drone cell). Another 69 varroa mites were found dead on the bottom board for a total of237 dead mites and 2 live mites (Fig. lb), resulting in 99.2% overall mortality ofvarroa mites in this treatment. The varroa mite mortality in capped drone cells was 168/170 or 98.8%. The queen was not lost (Westervelt, 2006). Attending the demonstration were David Webb (Webbs Honey), Jerry Hayes (Florida DPI), David Westervelt (Florida DPI), and Jerry Latner (Dadant and Sons, Inc.). (2) August 15, Temperature was 94 F (34.4 C), relative humidity was 58%; partly cloudy with an intermittent east wind at 0-10 mph. Fumigators were removed on 16 August 2006, starting at 10:30 am (after 21 hours) and mite numbers and mortality were recorded from 100 capped drone cells per colony (Table 1). Table 6. October 23, 2006 treatments. Alcohol washes (mites per hive) and strengths. I Mean26.5 Sum247 C1234 C1341 C14 C19 Cll C1826 C15 C16 C2046 C Strength ] ]863 ] ] Pre-trt Oct Post-trt Hive ] Post-trt

7 Vo!. 33, No.2 Intemat. J. Acaro!. 7 Table 7. January 2, 2007 treatments at Duda Ranch, Pineda, Florida using 90 ml 50 % formic acid + 15 ml HBH on 2 January Mites were counted from 100 capped drone or worker cells per hive on January 3, Bold type in mortality column indicates old dark comb II I 207 %Mortalitv I100.00I Dead Total I Alive Infested Mean Mortality = 93.15% # Cells The resulting average mortality of varroa mites in capped drone cells was 92.59% (range of77.1 to 100%). Control colonies had an average mortality of 1.72% (Table 2); alcohol washes showed a decrease from 2.6 to 1.1 varroa mites per hive in the treated colonies compared to untreated controls (6.3 and 12.6 mites per hive) (Table 3). The colonies were in moderately good shape with an average of 5.7 and 6.9 strength assessments (based on 10 points). Mite mortality was significantly higher in formic acid treated hives (df= 1, 18; F = 70.11, P<O.OOl). (3) October 23, Temperature was 80 F (26.7 C) and RH 33.5%. The sky was clear with a steady north wind at mph (the season's first cold front passed that day). Ten controls received 15 m1ofhbh and 110 m1 of water. Fumigators were removed October 24, 2006 starting at 10:00 am and mite numbers and mortality were recorded from 100 capped drone cells per colony (Table 4). The average mortality of varroa mites in Table 8. January 2, 2007 treatments at Duda Ranch, Pineda, Florida. Ten control colonies given 90 m1water + 15 ml HBH. Mite counts were made on January 3, 2007 from 100 worker and drone brood cells (four hives with drone) per hive. 17% Hive Total a a Dead a Alive %Mortalitv Mites #Cells 1 Inf Mean = 2.94%

8 8 Amrine et al Table 9. January 2, 2007 treatments at Duda Ranch, Pineda, Florida. Alcohol washes (mites per hive) and strengths. 2.28%. An unusually high mortality (15.9%) was found in colony 13, perhaps due to heat from sunlight (Table 5). Mite mortality was significantly higher in formic acid treated hives (df = 1, 27; F = , P<0.001). (4) January 2-3, Fumigators were removed 3 January starting at 10:15 am and mite numbers and mortality were recorded from 100 capped worker or drone cells per colony (Table 7). The average mortality of varroa mites in capped brood cells was 93.15% (range from 66.7% to 100%). The average mortality of control colonies was 2.94% (Table 8). The control mortality was skewed upward by colony C6 which had one dead mite out of four (Table 8). In this January treatment drone brood was minimal: only 4 of the 20 treated colonies had drone brood present. Mite mortality was significantly higher in formic acid treated hives (df = 1, 26; F = , P<0.0001). DISCUSSION Control of varroa mites in capped brood cells in our four treatments was excellent; the treatments were highly significant with large F values (ANOVA). The application of about three ounces of 50% formic acid mixed with ½ ounce of HBH resulted in an average mortality of 94.61% (mean of the four average mortalities). This value is high, especially considering that the April treatment (demonstration) was a single colony with no control. The overall average mortality was 93.29%; the average control mortality was 2.39%. Employing Abbott s Formula to adjust for control mortality (2.39%), a more realistic estimate of overall mortality of varroa mites in capped drone cells was [( )/( )] *100 = 93%. To our knowledge, no other pesticide or treatment for varroa mites has reported mortality this high in capped drone cells. The remarkable characteristics of this treatment are that it is very simple to apply and takes it less than 24 hours. Twenty colonies can be treated in an hour. Modifications to this method may improve handling time (trials to be made in April, 2007; Fig. 2). Queen losses were minimal, thanks to the application of Honey-B-Healthy. The citral and geraniol in lemongrass essential oil are identical to those in the Nasanov gland; they restore order to the bees, and eliminate the tendency for workers to ball the queen in the presence of harsh chemicals (HBH may also mitigate queen losses when fume boards are used to drive bees out of honey supers [boxes of 10 frames each for storing surplus honey]). Overall, alcohol washes showed mixed results. In our August treatments (Table 3), numbers of mites in the alcohol washes stayed relatively stable and low, even though the control colonies were only about 25 feet away. In 13 days after the treatments, the number of mites on treated bees went down to 1.1 mites per sample, whereas the number of mites on near-by control colonies increased from 6.2 to 12.6 per sample. To us, this indicated that mite influx (reinvasion) was minimal at that

9 Vol. 33, No. 2 Internat. J. Acarol. 9 Fig. 2. Number of mites by dates, January 2, 3 and 10, 2007, for alcohol washes from 50 % formic acid fumigated colonies in Rockledge, Florida (see Tables 9 and 10). Mean bars with different letters are significantly different at P < 0.05 with Tukey's test. time of year, under those conditions. On October 23, 2006, we noticed that there was a great influx (reinvasion) of varroa mites, causing our alcohol washes to have unusually high numbers despite high mortality in brood cells. We believe that the passing cold front stimulated workers and drones from weak and collapsing colonies in the region to seek queenright colonies. The January treatments on the Duda Ranch showed great reduction of varroa mites in the subsequent alcohol washes (Table 9). Apparently, drift of bees and influx of mites were minimal at this time compared to October. Table 9 and Fig. 2 show the significant differences between the low alcohol washes compared to the pretreatment wash and control washes. On the day after treatment, we believe a few dead varroa mites killed by formic acid, still resided under bee tergites. Thus, next day alcohol washes may not be very accurate. Since January 2007, mite numbers have resurged in all of David Webb s 550 colonies. Overall, the colonies are strong and bees are mostly healthy and free of pathogens despite the increased presence of varroa mites in the alcohol washes. David successfully pollinated a blueberry crop with 250 colonies in February 2007; in the same crop, other beekeepers had supplied 350 colonies. The condition and health of those other colonies were variable, but we assume that robbing, drift of workers, lost bees from die-outs and drone drift were the major cause of such a rapid influx of varroa mites in the alcohol washes of adult bees (David reported numbers in the 20s and 30s per hive sample.). Inspection showed a number of his colonies with old black comb which resulted in lower mortality in drone brood cells (Table 4, FA13, FA18 and FA21, which had a combined average control of 71.9%) and Table 7, FA4, FA5 and FA11 with a combined control of 70.4%. Throughout Florida, enormous numbers of colonies have died since November; obviously, the influx ('reinvasion') of varroa mites due to robbing, worker drift, drone drift, and lost bees from die-outs is very high (Renz, 2003). In contrast, in Maryland and West Virginia numbers of varroa mites remain very low after formic acid treatment because of the extreme isolation of most apiaries compared to Florida, Texas, California and other southern states and northern states like Pennsylvania, New Jersey and New York with sizable agricultural crops requiring commercial pollination and subsequent large movements of bee hives and their mites and pathogens (Goltz, 1987). Overall results of our four treatments show an average of 93% control (after adjustment with Abbott s Formula) (Anonymous, 1981) of varroa mites in capped drone cells. This is excellent control of varroa mites in honey bee colonies in April, August, October, and January. DISCLAIMER This article is a report of research and not a general recommendation for varroa mite control. Please contact your state/provincial apiarist to determine the policy for using formic acid and other varroa mite controls in your area. Formic acid is toxic and can cause skin and liver damage if the user is careless or spills the acid (MSDS, 2005). Always wear gloves, respirator and protective clothing when using formic acid; keep plentiful fresh wa-

10 10 Amrine eta/ using formic acid and other varroa mite controls in your area. Formic acid is toxic and can cause skin and liver damage if the user is careless or spills the acid (MSDS, 2005). Always wear gloves, respirator and protective clothing when using formic acid; keep plentiful fresh water at hand for emergency use. However, the advantages and simplicity of using this method far outweighs its disadvantages, and in the present situation of strong mite resistance to synthetic acaricides, widespread colony collapse disorder (CCD), and general decline of the beekeeping industry, we believe that it should receive emergency exemption for use. Formic acid is already found in honey in small amounts; it is a natural product found in ants, nettles and other organisms. Formic acid is a forage preservative: 2 liters of 90% formic acid are sometimes added to each metric ton of lucerne hay by many farmers in Europe; the formic acid preserves amino acids and protein and results in weight gain (Lafitte, 2007). It should be noted that there are usually a handful of dead young emerging workers at the entrance of the hives after the treatments of formic acid but this is a sign of a good treatment. These few workers are quickly replaced by strong colonies and their loss is of no consequence. ACKNOWLEDGMENTS We thank recently deceased Dr. George Seidel, WVU Agr. and Forestry Experiment Station Statistician for statistical analysis of our research data. The authors are grateful to the Florida Department of Agriculture, Division of Plant Industy, for the support of this research. Weare also grateful to our families for supporting us and our research during the past several months. We owe great thanks to Dr. Yong-Lak Park, our new entomologist at WVU, for helping with the statistical analyses. Helping us with the research were Jerry, Mary and Gary Turner, J.J. and Jacob Tilton, John Gentzel, Mark Almeter, Dimitry Albertese, Alberto Santini, Malcolm Brinson, Mark Altmeyer, Daniel Amrine, David Amrine, Tony Delia, Art Sternheimer and Gary Ranker. Without their help, this research could not have been completed. They made it possible for us to carefully examine 2000 to 3000 drone brood cells after each treatment. To date, there are many commercial and hobbyist beekeepers in Florida using all or parts of our protocol to keep their colonies alive and healthy; we thank them for their encouragement and the considerable feedback that helps us to improve our methods. We owe great thanks to Dr. Barton Baker, Director of the Division of Plant and Soil Sciences, Davis College of Agriculture and Forestry, West Virginia University, for continuing to support our research and teaching in beekeeping over the past 29 years; we believe this shows true dedication to keeping a critical science alive when it has died at so many other eastern universities. REFERENCES Amrine, J. W., Jr., T. A. Stasny and R. Skidmore New mite controls investigated. Amer. Bee Jour. 136(9): 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-i-5985), 28 Dec 2001: 11pp. Amrine, J. W., Jr. and R. Noel Formic acid fumigator for controlling varroa mites. Internat. J. Acarol. 32(2): ( varroa06). Anonymous Instructions for determining the susceptibility or resistance of mosquito larvae to insect development inhibitors. World Health Organization, Geneva (WHONBC/81.812). Anonymous European group for integrated varroa control. Forschungsanstalt Agroscope Liebefeld Posieux ALP, /00567/index.html?lang=de. Last accessed 27 April Barrionuevo, A Honeybees vanish, leaving keepers in peril. A disappearing act for bees. nytimes. com/2 007/02/27 /bus iness/2 7bees. html? ex = &en= Ige542jb &ei=5070&e mc=etal. NY Times Multimedia Presentation [1 March 2007]. Bitenc, J. and J. Snajder A new type offormic dispenser for varroa mite control. Apimondia XXXVlIIth Congress, APIMONDIA-Ljubljana Slovenia, August Abstract number 156, 4 pp. slovenia/en/ bitenc.pdf Last accessed 26 April Calderone, N Effective fall treatment of Varroa jacobsoni (Acari: Varroidae) with a new formulation of formic acid in colonies of Apis mellifera (Hymenoptera: Apidae) in the Northeastern United States. J. Econ. Entomol. 93(4): Calderone, N. W Integrated pest management for Varroa destructor in the northeastern United States using drone brood removal and formic acid. IPM chemical control methods. USDA SARE Agricultural Innovations (16 pp, refereed extension article). 05_ 07.htm. Last accessed 27 April Eguaras, M., M. Del Hoyo, M. A. Palacio, S. Ruffinengo, E. L. Bedascarrasbure A new product with formic acid for Varroa jacobsoni Oud. control in Argentina. I. Efficacy. J. Vet.. Med. Series B. 48(1): Eischen, F. A Trials (and tribulations) with formic acid for varroa control. Amer. Bee J. 138: Elzen, P. J., D. Westervelt and R. Lucas Formic acid treatment for control of Varroa destructor I,

11 Vol. 33, No.2 Internat. 1. Acarol. 11 (Mesostigmata: Varroidae) and safety to Apis mellifera (Hymenoptera: Apidae) under southern United States conditions. 1. Econ. Entomol. 97(5): Ellis, M. D. and F. P. Baxdale Comparison offormic acid sampling with other methods used to detect varroa mites (Varroajacobsoni Oud.) and mite distribution within colonies in Nebraska. Bee Science 3: Fakhimzadeh, K Potential of super-fine ground plain white sugar dusting as an ecological tool for the control of varroasis in the honeybee (Apis mellifera). Amer. Bee Jour. 140(6): Fox News Home/Detail.jsessionid=82D03782CB8A 7BD814 E7D 162A338C4F A?contentId= &version =2&locale= EN- US&layoutCode=TSTY &pageid= Accessed February Fry, 1. C One-way analysis of variance. pp In: Fry, 1. C. (Ed.). Biological data analysis: a practical approach. Oxford University u.k. Press. Oxford, Goltz, L Migratory beekeeping. Amer. Bee Jour. 127(1): 29-32, 34-35, Goodwin, M. and C. Van Eaton Control of Varroa. A Guide for New Zealand Beekeepers. New Zealand Minis. Agr. Forestry, Wellington, NZ. 127 pp. Hayes, Loss of honey bee populations. A threat to US Agriculture. Southeast Farm Press. Wednesday, 14 Mar 2007: 22, 23. Honeybee World com/ diary/2 000/diary htm #Formic October 11. Accessed 25 April Hunt, S Honeybee Disaster. Columbus Dispatch, Tuesday, 13 March 2007, AI, A4. Imdorf, A., 1. Charriere and P. Rosenkranz Varroa control with formic acid. Coordination in Europe of research on integrated control of varroa mite in honey bee colonies, Agricultural Research Centre, Merelbeke, Belgium, Commission of the European Communities. pp Lafitte, M Formic acid. uk/motm/formic.htm. Accessed 26 March Latsch, G Collapsing colonies. Are GM Crops Killing Bees? SPIEGEL ONLINE, 22 March 2007, 18:21. URL: ,473166, OO.html. 24 March Accessed, MAAREC (Mid-Atlantic Apiculture Research, Education, etc.) html; ases/colonycollaps edisorder WG.html. Accessed February Martin, S. J Varroajacobsonipopulation biology research in the UK. Amer. Bee Jour. 137(5): MSDS Number F5956, 08/30/05, baker. com/msds/ englishhtml/f5 956/htmhttp:// englishhtml/f5 956.htm. Acessed 29 March Noel, R Organic treatments for controlling varroa mites and pathogens in Florida. 50megs. comljlorida,htm Last accessed 26 April Noel, B. and 1. W. Amrine, Jr More on essential oils for mite control. Amer. Bee Jour. 136(12): ( Noel, R., Amrine, J. and A. Kovacs Organic treatment IPM for honey bee mites. Amer. Bee Jour. 142(5): Noel, R., Amrine, 1. and A. Kovacs Integrated pest management combined with mite resistant queens to combat acaricide-resistant varroa. Amer. Bee Jour. 142(9): PSU (Pennsylvania State University, Entomology Dept.) Accessed February Renz, M Die Populationsdynamik der Bienenmilbe Varroa destructor bei V61kern von Apis mellifera unter besonderer Beriicksichtigung der Reinvasion. Ph. D. thesis, Institut fur Parasitologie und internationale Tiergesundendheit, Fachbereich Veterinarmedizin, Freie Universitat, Berlin. 163 pp. Sanford, M. T Sampling for varroa. Apis 13(8): 1. SAS Institute SAS Online Doc, SAS Institute, Cary, NC. Teague, D A buzzkill for farmers nationwide. article + video. Accessed 24 March Van Engelsdorp, D Twenty four hour fumigation of colonies with formic and acetic acid for the control of varroa mites, small hive beetle, honey bee tracheal mites, and honey bee viruses. National Honey Board, Monthly Report, December Westervelt, D Environmental specialist, Division of Plant Industries, Florida Department of Agriculture, Gainesville, FL. Personal communication ( ) 24 April *****