Article

A comparison of two methods of applying oxalic acid for control of varroa

Taylor & Francis
Journal of Apicultural Research
Authors:
  • Crop Diversification Center North, Edmonton, AB, Canada
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... Veterinary drugs with these organic acids are freely available today [8]. Oxalic acid is not known to have a negative effect on honey bee health, hive development, or behaviour [11][12][13][14][15][16][17][18][19]. Oxalic acid is a natural compound in honey [20] and there is a low risk of accumulation in wax and honey [13,21,22]. ...
... "Bottom board sampling" means counting fallen mites before or after treatment on the bottom board of the hive. To guarantee the most comprehensive count and to avoid reinfestation, some studies used protective nets [60] or sticky bottom boards [1,[15][16][17][18][19]22,[32][33][34]38,[42][43][44][45]47,51,[55][56][57]. ...
... In some literature sources of the Tun group, the volume of trickled solution was not . Efficacy values and annual median efficacy of "trickling"; References [1,[13][14][15][16]18,19,32,33,[41][42][43][44][45][46][50][51][52][53][54]56,[58][59][60][61][62][63][64][66][67][68][70][71][72][73][74][75]77,80,81,84,85,87,89,[91][92][93][94][95][96][97] correspond to the numbered data points. T 1 comprises data over a period from 1998 to 2013, T 2 from 1998 to 2019, T 3 from 1997 to 2017, T 4 from 2001 to 2020, T 5 from 2005 to 2020, T 6 from 2004 to 2020, and T un from 1998 to 2020. ...
Article
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As Varroa destructor is one of the most important pathogens of Apis mellifera, there are numerous treatment methods, including pharmaceutical and biotechnological approaches. However, the rapid development of resistance to synthetic acaricides by Varroa destructor has become a significant concern. To date, there have been no investigations into the development of resistance to organic acids. This review examines the potential risk of oxalic acid resistance development by evaluating literature sources from the past 30 years following the PRISMA 2020 guidelines. Median annual efficacies are calculated and reviewed over time for several application methods. An efficacy higher than 70% is determined as not resistant. Independent of the method of application, no resistance development can be observed, although there are some outliers of the annual median. These outliers can be explained by brood status or study setting. However, the result is limited by the low number of efficacy values, and further standardised studies are needed.
... Numerous experiments have been conducted to evaluate the efficiency of different oxalic acid concentrations and application methods used to control varroa in broodless or broodright colonies. In broodless colonies, the spraying of weak solutions of oxalic acid onto bees had very high efficiency (> 95% mite mortality) (Nanetti et al., 1995;Imdorf et al., 1997;Bahreini, 2003) and the trickling of solutions of sugar and oxalic acid onto honey bees had an efficiency higher than 90% (Charrière & Imdorf, 2002;Bahreini, 2003). In broodright colonies, efficiencies of 39% and 48%, according to acid concentration, were achieved after three treatments (Gregorc & Planinc, 2001) administered by trickling, while an efficiency of 24% was reported after one spring treatment (Brødsgaard et al., 1999) using the trickling method. ...
... Numerous experiments have been conducted to evaluate the efficiency of different oxalic acid concentrations and application methods used to control varroa in broodless or broodright colonies. In broodless colonies, the spraying of weak solutions of oxalic acid onto bees had very high efficiency (> 95% mite mortality) (Nanetti et al., 1995;Imdorf et al., 1997;Bahreini, 2003) and the trickling of solutions of sugar and oxalic acid onto honey bees had an efficiency higher than 90% (Charrière & Imdorf, 2002;Bahreini, 2003). In broodright colonies, efficiencies of 39% and 48%, according to acid concentration, were achieved after three treatments (Gregorc & Planinc, 2001) administered by trickling, while an efficiency of 24% was reported after one spring treatment (Brødsgaard et al., 1999) using the trickling method. ...
... Numerous experiments have been conducted to evaluate the efficiency of different oxalic acid concentrations and application methods used to control varroa in broodless or broodright colonies. In broodless colonies, the spraying of weak solutions of oxalic acid onto bees had very high efficiency (> 95% mite mortality) (Nanetti et al., 1995;Imdorf et al., 1997;Bahreini, 2003) and the trickling of solutions of sugar and oxalic acid onto honey bees had an efficiency higher than 90% (Charrière & Imdorf, 2002;Bahreini, 2003). In broodright colonies, efficiencies of 39% and 48%, according to acid concentration, were achieved after three treatments (Gregorc & Planinc, 2001) administered by trickling, while an efficiency of 24% was reported after one spring treatment (Brødsgaard et al., 1999) using the trickling method. ...
... Numerous experiments have been conducted to evaluate the efficiency of different oxalic acid concentrations and application methods used to control varroa in broodless or broodright colonies. In broodless colonies, the spraying of weak solutions of oxalic acid onto bees had very high efficiency (> 95% mite mortality) (Nanetti et al., 1995;Imdorf et al., 1997;Bahreini, 2003) and the trickling of solutions of sugar and oxalic acid onto honey bees had an efficiency higher than 90% (Charrière & Imdorf, 2002;Bahreini, 2003). In broodright colonies, efficiencies of 39% and 48%, according to acid concentration, were achieved after three treatments (Gregorc & Planinc, 2001) administered by trickling, while an efficiency of 24% was reported after one spring treatment (Brødsgaard et al., 1999) using the trickling method. ...
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The effects of oxalic acid administered by the trickling method on brood development of honey bee colonies were evaluated (a) by observing the development of marked cells of young (< 3 days old) and old (> 3 days old) larvae, and (b) by measuring the area of open brood for several weeks post application. Oxalic acid, dissolved in a 50% sugar solution, with an end concentration of 3% w/v oxalic acid, was applied twice by the trickling method during summer to 10 colonies. A high percentage of young (12.6% and 9.5%) and old honey bee larvae (10.6% and 5.6%) were removed from their cells after the first and second oxalic acid applications, respectively. The surface of the open brood area was also reduced by 17.5% after the two oxalic acid applications and stayed low for about two months. For the same period of time the open brood area in 10 control colonies increased by 34.5%. The two oxalic acid applications removed 60 ± 12% of varroa mites adhering to adult honey bees, while the natural fall of mites measured in control colonies (for a period of 40 days) was 32 ± 4%. Combining the detrimental effect on brood development with the low relative effectiveness on varroa removal, oxalic acid application by the trickling method when open brood is present is not as safe as has been regarded in the past. Consideration needs to be given to the use of different sugar and oxalic acid concentrations in the treatment solution in order to minimize its adverse effects on open honey bee brood.
... In response, beekeepers are showing a growing interest in treatments that work on physical intolerance rather than enzyme degradation, as is the case with synthetic acaricides, to which resistance develops. Therefore, natural chemicals such as organic acids, essential oils, and their derivatives are increasingly used [30,31]. However, several studies suggest that the use of organic acids against Varroa may be harmful to bees. ...
Article
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Essential oils and their components are generally known for their acaricidal effects and are used as an alternative to control the population of the Varroa destructor instead of synthetic acaricides. However, for many essential oils, the exact acaricidal effect against Varroa mites, as well as the effect against honey bees, is not known. In this study, 30 different essential oils were screened by using a glass-vial residual bioassay. Essential oils showing varroacidal efficacy > 70% were tested by the complete exposure assay. A total of five bees and five mites were placed in the Petri dishes in five replications for each concentration of essential oil. Mite and bee mortality rates were assessed after 4, 24, 48, and 72 h. The LC50 values and selectivity ratio (SR) were calculated. For essential oils with the best selectivity ratio, their main components were detected and quantified by GC-MS/MS. The results suggest that the most suitable oils are peppermint and manuka (SR > 9), followed by oregano, litsea (SR > 5), carrot, and cinnamon (SR > 4). Additionally, these oils showed a trend of the increased value of selective ratio over time. All these oils seem to be better than thymol (SR < 3.2), which is commonly used in beekeeping practice. However, the possible use of these essential oils has yet to be verified in beekeeping practice.
... Similarly, Coffey and Breen (2016) reported 81.5% mite control efficacy when using the trickling method to apply oxalic acid in hives. However, several researchers have pointed out the need for more than one treatment in colonies that have brood (Mutinelli et al. 1997;Bahreini 2003;Giovenazzo and Dubreuil 2011). In fact, Emsen et al. (2007) treated colonies containing brood with oxalic acid using the trickling method during early fall and in the same location where this study was conducted, and they found an average rate of varroa mite control below 40%. ...
Article
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The ectoparasitic mite Varroa destructor is responsible for the death of millions of honey bee (Apis mellifera) colonies worldwide. Testing potential miticide compounds with different delivery methods that effectively control V. destructor and have low toxicity for honey bees is crucial to manage this parasite in hives. We determined the varroacide efficacy of three natural compounds delivered to hives with three application methods over a 4-week period. Oxalic acid in a sucrose solution was applied impregnated in cardboard (T1). A mixture of oregano and clove oils in an ethanol-gelatin solution was applied impregnated in absorbent pads (T2). Oregano oil alone was delivered using electric vaporizers (T3) to test the hypothesis that continuous release of miticides increases the varroacidal efficacy of essential oils. The varroa mite control rates for treatments T1–T3 were 76.5 ± 7.11, 57.8 ± 12.79 and 97.4 ± 0.68%, respectively, and there were no differences for bee mortality between control and treatments 1 and 3. Additionally, most mites were killed in the first 2 weeks in T3 colonies compared to the last 2 weeks in colonies of the other treatments. These results demonstrate the importance of continuously releasing natural miticides to achieve safe and high rates of mite control in hives. They also show that oregano oil may be an effective miticide against V. destructor infestations in colonies.
... In response, beekeepers have shown their interest in chemical treatments that operate on physical tolerances rather than enzyme degradation, as a resistance to synthetic pesticides. Natural chemicals, such as formic acid, oxalic acid, lactic acid, thymol eucalyptus, camphor, menthol, thyme oil, laurel, and lavender oils have been recommended and used in recent years (Aydın, Cakmak, & Cakmak, 2007;Aydın, Senlik, & Girisgin, 2009;Bahreini, 2003;Esmen, Dodologlu, & Genç, 2010;Girisgin, 2008). Since organic acids appear to be less harmful to human health and are naturally found in the chemical structure of honey, they are suggested in the process of producing organic and healthy hive products (Esmen et al., 2010;Kumova, 2003;Smodiš Škerl, Nakrst, Ž vokelj, & Gregorc, 2011). ...
Article
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Natural medicines such as formic acid, oxalic acid, thymol and menthol have recently been used as alternative treatments against the honey bee parasitic mite varroa. The aim of this study was to observe and examine their impact on Heat Shock Proteins (HSP 70) in the brain tissues of bees. For this purpose, seven different treatment groups were created using various concentrations and administrations of formic and oxalic acid and thymol-menthol mixtures, including positive (untreated) and negative controls. The results showed that in the groups exposed to the varroa treatments, HSP 70 results were lower than those of the non-treated groups. HSP 70 results were lowest in the thymol-menthol mixture exposed group among the treated groups. We conclude that it would be more beneficial to prefer natural medicines against varroa, which lead to lower HSP 70 results which are the molecular determinants of stress.
... Some experiments have shown that a single spray with OA in aqueous or sucrose solution is considerably more effective than trickling (Brødsgaard et al., 1999;Bahreini, 2003), indicating that greater wetting of bees increases the effectiveness of the oxalic acid in mite control. Our submersion tests also showed the importance of thorough wetting for good mite control. ...
Article
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The toxicity of various concentrations of oxalic acid dihydrate (OA) in aqueous and sucrose solution to Varroa destructor and to honey bees (Apis mellifera) was assessed using submersion tests of caged bees and by spraying bees in colonies with and without brood. An aqueous solution of 0.5% OA gave effective control of the mite and was non-toxic to bees whereas higher concentrations of OA (1.0-2.0%) were highly toxic to bees. Submersion tests into solutions with 0.1% OA were acaricidal both in aqueous (59.9 ± 3.7 %) and in 50% sucrose solution (71.1 ± 4.2%) whereas concentrations of 0.2-0.5% OA were highly effective; OA in sucrose solution was more toxic to bees than OA in the aqueous solution. Spraying with 0.5% OA solution at a dose of 25 mL per comb in May 2003 and in April 2004 was 99.01-99.42% effective in mite control in Estonian standard one box long beehives with 22 frames (each 414 × 277 mm, area 1000 cm2 per comb side). Most mites fell after the first spraying. In autumn, spraying test colonies that had little capped brood once or twice with a 0.5% OA solution gave effective mite control (92.94 ± 0.01% and 91.84 ± 0.02%, respectively) with no noticeable toxicity to bees.
Article
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Formic acid and oxalic acid field trials for control of Varroa destructor were carried out in autumn according to the Swiss prescriptions during three successive years in different apiaries in Switzerland. The following parameters were determined in honey that was harvested the year after treatment: formic acid, ox- alic acid and free acidity. The following range of values were found in honeys of untreated colonies: formic acid, from 17 to 284 mg/kg, n = 34; oxalic acid, from 11 to 119 mg/kg, n = 33. There was a small, but unproblematic increase in formic acid levels in comparison to the levels in the controls; average: 46 mg/kg, maximum: 139 mg/kg. No increase in formic acid was found with increasing number of treatment years. If emergency formic acid treatments were carried out in spring, the residue levels were much higher: average in- crease of 193 mg/kg, maximum 417 mg/kg. The oxalic acid content remained unchanged, even after two suc- cessive treatments during the same autumn. No rise of free acidity was encountered after a combined treatment with formic and oxalic acid during the three trial years. honey/residue/formic acid/oxalic acid/free acidity/Varroa destructor
Article
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Essential oils and essential oil components offer an attractive alternative to synthetic acaricides for the control of Varroa jacobsoni. They are generally inexpensive and most pose few health risks. Terpenes (mainly monoterpenes) are the main components of essential oils, comprising about 90 % of the total. More than 150 essential oils and components of essential oils have been evaluated in laboratory screening tests. Very few of them, however, have proven successful when tested in field trials. Thymol and thymol blended with essential oils or essential oil components offer a promising exception. Mite mortality obtained with these formulations typically exceeds 90 % and often approaches 100 %. In addition, residues in honey are low, even after long-term treatments. The exact conditions under which these formulations will yield reliable and effective control, however, have only been determined for certain European regions. Based on the available studies, relying solely on a single treatment with an essential oil or essential oil component is generally not sufficient to maintain mite populations below the economic injury level. Therefore, efforts are necessary to optimize the use of these substances and to incorporate them, along with other measures for limiting mite populations, into an integrated pest management strategy for control of Varroa jacobsoni. © Inra/DIB/AGIB/ Elsevier, Paris
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