1. INTRODUCTION

On a worldwide basis, hundreds of mate-rials have been tested to control the para-sitic honey bee mite (Shimanuki et al., 1992),Varroa destructor, formerly referred to asVarroa jacobsoni Oudemans, (Anderson,2000; Anderson and Trueman, 2000). In

view of the sucking structure of the ambu-lacrum of these mites (Ritter, 1981; Liu andPeng, 1990), dusts of various materials suchas finely ground glucose, pollen or wheatflour sprinkled onto the bees on the combshave been tried as controls for the mite(Shah and Shah, 1988; Ramirez 1989;Loglio and Pinessi, 1991; 1992; 1993;

Apidologie 32 (2001) 139148 139 INRA/DIB-AGIB/EDP Sciences, 2001

* Correspondence and reprintsE-mail: kamran.fakhimzadeh@helsinki.fi

Original article

Effectiveness of confectioner sugar dustingto knock down Varroa destructor

from adult honey bees in laboratory trials

Kamran FAKHIMZADEH*

Department of Applied Zoology, PO Box 27 (Viikki C),00014 University of Helsinki, Finland

(Received 26 June 2000; revised 4 September 2000; accepted 27 December 2000)

Abstract Direct and air-assisted dusting of fine confectioner sugar (2540 m m mean particle size)with and without pre-anesthesia of honey bees by CO2 were studied as a physical control method ofVarroa destructor under laboratory conditions on samples of 78 bees (range 49107). CO2 anesthe-sia alone had no effect, while sugar dusting resulted in significant mite knock down. CO2 anesthesiadid not affect the effectiveness of sugar dusting, and mean mite fall over 2 days resulting from directdusting with 5 g sugar and from air-assisted dusting with 0.5 g sugar per sample was 91% and 62%,respectively, and this difference was significant (P = 0.001). Ninety-nine percent of the mites in thesugar treatment fell within 18 h of treatment. As a possible side-effect of the dusting, the presence ofsugar particles in the T2 spiracles and their tracheal ducts from treated honey bees was investigatedunder scanning electron microscope. No sugar particles were found in them.

Varroa destructor / varroosis control / dusting / CO2 / tracheal ducts

Loglio, 1996). Dust particles adhere to theambulacrum of V. destructor and preventthe mites from adhering to the bees or othersurfaces (Ramirez, 1989). The mites thenfall down to the bottom of the hive wherethey starve to death, as they are unable tomove on the dusty surface (Ramirez andMalavasi, 1991; Ramirez, 1994). Encour-aging results were obtained in these trials,especially in the absence of brood, but theparticle sizes of the dusts used were notreported. Fakhimzadeh (2000) tested theeffect on V. destructor of dusting with anair sprayer 15 and 20 g of confectioner sugarwith particle sizes mostly below 40 m m ontoone and two-story colonies, respectively,and he found significant mite fall after thetreatments. Similarly, by dusting adult bees(ca. 350 individuals) with confectioner sugarin a wide mouth jar, Macedo and Ellis(2000) found that a high number of miteswere dislodged from the bees.

The impact of such dusting on honey beesis not well known. The breathing apertures ofthe honey bee consist of ten pairs of spiraclesin both larva and adult, from T2 to A8 (Dade,1977; Erickson et al., 1986; Snodgrass andErickson, 1992). All spiracles have muscle-operated valves, except for the T3 spiracleswhich are minute and lie between the upperends of the mesepimeron and the metapleu-ron. Both active and inactive honey beesinhale through the T2 spiracles by the pump-ing movements of the abdomen (Bailey,1954; Snodgrass, 1956). The valve of T2spiracles can not be completely closed,hence the tracheal mite Acarapis woodi Ren-nie is able to enter this spiracle, but none ofthe others (Dade, 1977). Similarly, confec-tioner sugar particles used for the controlof V. destructor could hypothetically pene-trate through T2 spiracle and interfere withthe breathing of the bees.

Two laboratory trials were conducted toquantify the effectiveness of confectionersugar dusting to knock down V. destructorand to determine whether the sugar particlescould penetrate into the respiratory system

of honey bees through T2 spiracles. Anotherobjective was to study the impact of CO2on V. destructor, as it had not been investi-gated previously. CO2 anaesthesia was usedwith the assumption that it might drive themites out from between the segments on thebody of the bees and also in order to anaes-thetise the bees so that they would not inhaleexcess confectioner sugar during the dustingtreatments.

2. MATERIALS AND METHODS

The studies were conducted in the sum-mer 1997 and 1998 at the Viikki experi-mental apiary (60 13 N, 25 02 E) of theUniversity of Helsinki. Bees were brushedfrom brood combs directly into glass con-tainers of ca. 430 cm3, covered by a net onthe top. A piece of bee candy was providedfor food, and a strip of wax foundation wasalso provided inside the jar to facilitate beemovements.

The confectioner sugar used in all exper-iments, including preliminary ones since1990 (Fakhimzadeh, 2000), consisted offinely ground pure white sucrose withoutstarch or other additive with a nominal meanparticle size of 2540 m m according to themanufacturer (Finnsugar Ltd.; Helsinki, Fin-land). This size distribution was confirmedby examining the sugar particles with scan-ning electron microscopy (SEM; Fig. 1).

2.1. Experiment 1

Samples of 49 to 107 honey bees (mean78) were taken from 6 colonies. The fol-lowing 7 treatments were used with a com-pletely randomised design and 5 replicateseach:

A: Direct dusting of 5 g of confectionersugar poured directly onto the sample ofbees through the net.

B: Dusting of 0.5 g of confectioner sugaronto the sample of bees through the netusing the airflow of a simple blower as a

K. Fakhimzadeh140

carrier. This air blower consisted on a600 cm3 vacuum jar, in which the sugar wasplaced, connected to a foot air pump(Fakhimzadeh, 2000).

CA: Sample of bees anaesthetised byCO2 and immediately treated with directdusting as in A.

CB: Sample of bees anaesthetised by CO2and immediately treated as in B.

C: Sample of bees only anaesthetised byCO2.

D1: Sample of bees shaken and rolled inthe jar for a few seconds (shaken control).

D2: Samples of bees kept alongside theothers without any treatment (untreated con-trol).

Except for the untreated control, all sam-ples were shaken immediately after treat-ment and rolled gently for a few seconds sothat the sugar particles covered them evenly.

The anesthesia was administered so as toknock down all the bees in a sample. All thejars were then placed in darkness and upsidedown on top of larger, wide-mouth jars, andthey remained in this position during theassay to catch any fallen mites and/or sugarparticles.

Dead bees and fallen mites were counteddaily for the next 2 days. The counting ofdead bees was improved by moving eachglass jar several times from side to side. Onthe third day, the rest of the bees were killedand shaken mechanically for 30 min in 70%ethanol to remove the remaining mites asthis method removes 100% of the mites in asample (De Jong et al., 1982; Shimanukiand Knox, 1991). For each replicate, theeffectiveness of the treatment was calcu-lated by dividing the number mites knockeddown over 2 days by the total number ofmites in the sample. Total number of mites

Sugar dusting as a control method of Varroa destructor mites 141

Figure 1. Scanning electron micrograph of the finely ground confectioner sugar used in the study show-ing most particles less than 40 m m in diameter (bar = 30 m m).

and bees in each sample determined the miteinfestation level which was found to rangefrom 1 to 24 mites per 100 honey bees(mean 10 mites/100 bees).

The data consisted of two-way and multi-way tables with the numbers of mitesknocked-down or remaining on the bees andthe number of bees dead or alive for eachtest and each treatment after 18 and 42 h.I analysed these tables with G tests when-ever there were 5 or more observations percell (Sokal and Rohlf, 1995). Wheneverthere was a cell with a smaller frequency,the significant probability (P) was calcu-lated using 10000 Monte-Carlo simulationof the loglikelihood ratio (Engels, 1988).Overall, a total of 252 mites and 2,736 beeswere used in the analysis.

2.2. Experiment 2

Samples were prepared as in Experiment1, but from 3 other colonies with a lowerinfestation level, to assess the impact of con-fectioner sugar dusting on healthy and/orrelatively mildly infested bees. The mitenumbers in these samples were very low,with a maximum of 2.5 mites per 100 bees(2 mites in a sample which occurred in only4 samples). The experimental design wasagain completely randomised with fourreplicates for each treatment. The treatmentsin this experiment were A, B, CA and D2, asdescribed in Experiment 1, and we also usedtreatment C3A which was similar to treat-ment CA, but with 3 minutes of CO2 anaes-thesia. The respiration pattern of active andinactive bees changes due to the extent ofCO2 (Bailey, 1954; Snodgrass, 1956). Thistreatment was intended to show the impactof relatively high amount of CO2 on theinhalation of sugar particles. The rolling ofthe samples and their follow-up after treat-ment were as in Experiment 1.

As T2 spiracles and their ducts areinvolved in the inhalation of both active andinactive bees, I investigated only these partsfor possible effects of the sugar dusting. The

first examination of the tracheal ducts wasdone on the day following treatment, ca.18 h after treatment, and the second one wasdone on the following day. I used this sched-ule because after 2 days, the bees may havegroomed away the external sugar particles sothat the effect of sugar dusting may nolonger be visible. Ten bees per treatmentwere taken daily at random, and examinedfor the presence of sugar particles (total of200 ducts).

Bees were killed by dissecting and thetracheal ducts were removed with forcepsand dissected lengthwise. In order not towash the possible sugar particles from thetracheal ducts, specimens were air dried atroom temperature for 45 min. They werecoated with platinum in a sputter coater(Agar Scientific Ltd, Stamsted, UK), andobserved with a Jeol JSM-820 SEM (JeolLtd., Tokyo, Japan) at an accelerating volt-age of 10 kV. The specimens were scannedat 500 and 4 000 magnifications. Aftersugar dusting, the ambulacrum of femaleV. destructor were also examined underSEM to confirm the presence of sugar par-ticles on them.

3. RESULTS

3.1. Experiment 1

The mite fall results were homogeneousamong the 5 replicates for each treatmentand they were therefore pooled to comparetreatments. There were significant differ-ences among the treatments (G = 197.1,df = 6, P < 0.001), and also among the fourtreatments with confectioner sugar dusting(G = 16.63, df = 3, P < 0.001; Tab. I). Thecontrols with and without shaking androlling of the bees and the CO2 anaesthesiafollowed by shaking and rolling gave simi-lar results with a low mite fall of 0% and3% after 18 h and 42 h, respectively (Tab. I).The CO2 anaesthesia did not affect signifi-cantly the mite fall that resulted from thesugar dusting (Mantel-Haenszel chi-square

K. Fakhimzadeh142

for odds ratio homogeneity = 0.0178,P = 0.893) and so the values of the treat-ments with and without anaesthesia werepooled to compare the dusting treatments.The direct dusting of 5 g of confectionersugar resulted in 91% mite fall comparedto only 62% for the air-assisted dusting of0.5 g and this difference was significant(G = 15.89, P = 0.001).

The confectioner sugar dusting actedfairly quickly as almost all the mites thatfell were found 18 h after treatment: of99 fallen mites in the sugar treatment, only1 mite in A fell between 18 h and 42 h. Nomites fell in C, D1 and D2 within 18 h aftertreatment, and between 18 h and 42 h only 1,0 and 3 mites had fallen, respectively.

For the 7 treatments except A and B, beemortality was homogeneous among the5 replicates of each treatment with an aver-age mortality of 0.5% (Tab. I). In treatmentsA and B, bee mortality varied among repli-cates (P 0.001). In 3 replicates of treat-ment A and one replicate of B, mortalitywas similar to that recorded in the othertreatments, but in the 6 remaining replicates,it was much higher and ranged from 8% to26%.

3.2. Experiment 2

No sugar contamination was found insidethe tracheal ducts following any of the treat-ments. No obstruction of the spiracles T2with sugar particles was observed, so thiswas not the reason for the cleanliness of theexamined middle parts of the trachea. Fig-ure 2 shows the ambulacrum of a femalemite covered by many particles, which arelikely sugar particles resulting from thesugar dusting.

4. DISCUSSION

The mean effectiveness of mite knockdown with confectioner sugar was 91% withdirect dusting and 62% with air-assisteddusting (Tab. I). The former value is con-sistent with the 80% effectiveness reportedby Macedo and Ellis (2000) and also withthe results of previous studies on dustingwith confectioner sugar (Fakhimzadeh2000), and with fine glucose and wheat flourthat gave good results for mite control inthe absence of brood (Shah and Shah, 1988;Ramirez 1989; Loglio and Penessi 1992),and for the detection of live V. destructormites (Loglio and Penessi 1993; Loglio,

Sugar dusting as a control method of Varroa destructor mites 143

Table I. Effectiveness of V. destructor mites knock down and bee mortality after 42 h followingdusting of honey bee samples with 2540 m m confectioner sugar with or without prior CO2 anaesthesia(results from experiment 1 pooled over the 5 replicates).Treatment Number of mites Number of bees

knocked that remained dead alivedown on the bees

A (direct dusting with 5 g sugar) 32 24 28 349 B (air-assisted dusting with 0.5 g sugar) 20 11 35 311 CA (CO2 anaesthesia + A) 32 22 22 382CB (CO2 anaesthesia + B) 15 10 21 427C (CO2 anaesthesia) 11 43 21 388D1 (control with bees shaken and rolled) 10 50 25 427 D2 (control) 13 29 21 379 All bee samples were shaken and rolled after dusting (A, B, CA, CB) or anesthesia (C).

1996). The effectiveness of the direct dust-ing with 5 g confectioner sugar on miteknock down was also similar to that reportedfor mite kill in studies using chemical appli-cations, since the effectiveness of Amitrazand fluvalinate on V. destructor mites inpackage bees was found to be 83% and87%, respectively, following treatmentas recommended by the manufacturers(Henderson, 1988).

The significant difference in the effi-ciency of mite fall with 5 g and 0.5 g ofsugar was perhaps due to the fact that a smallamount of confectioner sugar is quicklygroomed away by bees. This may result inthe reduction of contact between sugar andthe mites, when they come out from betweenthe bee segments.

The direct dusting of 5 g of confectionersugar represented an average of 60 mg ofsugar per bee, which is more than half themass of a honey bee. Nevertheless, the fineparticles of sugar (< 40 m m; Fakhimzadeh,2000) did not enter to the trachea via breath-ing through T2 spiracles. This suggests thatthe presence of a dense hair cover sur-rounding these spiracles prevented their con-tamination with sugar particles. This maynot be so surprising since bees are in contactwith pollen grains throughout their adultlife, especially when foraging in flowerswith powdery pollen, and the pollen of mostplant species lies in the 2540 m m size range(Erdtman, 1952; Thorp, 1979). My resultssuggest that sugar particles did not pene-trate and accumulate in the tracheal ductsregardless of the amount and method of

K. Fakhimzadeh144

Figure 2. Scanning electron micrograph of the ambulacrum of a female V. destructor after confectionersugar dusting of a sample of honey bees. The arrows indicate particles which are likely sugar ones(bar = 10 m m).

application, and with or without pre-anaes-thesia of the bees. However, the cause ofthe high bee mortality recorded in somereplicates of treatments A and B in experi-ment 1 remains unknown as this mortalitydid not occur in any of the replicates of treat-ments CA or CB in which the bees weredusted with similar quantities of confec-tioner sugar as used in A and B, respectively.

The dusting method may be applicableto package bees for the control of mites(without anaesthesia, as it had no impact onmite fall). As the shaking and rolling of awhole colony is not practical, further labo-ratory investigation without shaking androlling the bees are needed to better simulatea method applicable to whole colonies toassess its effectiveness. The side-effects ofconfectioner sugar dusting on queens andbrood also needs to be measured beforebeing able to include this dusting methodin integrated pest management strategies tocontrol V. destructor mites.

ACKNOWLEDGMENTS

The research was supported by the Foundationof Alma and Jussi Jalkanen of the FinnishCultural Foundation, for which I am grateful.I thank H.M.T. Hokkanen, H. Shimanuki,A. Tinat, S. Rudvin, and two anonymous refereesand B.E. Vaissire for their significant effortsand valuable comments on the manuscript. I amthankful to A. Soltanpour, F. Mire, V.M. Vn-nen, J. Juhanoja, M.Viitasaari and S. Lehtinenfor their laboratory assistance and guidance withthe electron microscope procedure.

Rsum Efficacit du saupoudragede sucre de ptissier pour faire tomberVarroa destructor des abeilles domestiquesadultes lors dessais au laboratoire. Parceque lacarien Varroa destructor Andersonand Trueman (anciennement V. jacobsoniOudemans) possde un ambulacre avec unestructure absorbante, diverses poudres ontt testes comme moyen de lutte. De lafine poudre de glucose, du pollen broy oude la farine de bl ont t saupoudres sur les

abeilles sur les rayons pour faire tomber lesacariens des abeilles adultes et des rsultatsintressants ont t obtenus principalementen labsence de couvain. Le but principalde ltude tait de dterminer de faon plusprcise lefficacit du saupoudrage de sucrede ptissier en conditions de laboratoire pourlutter contre V. destructor. On a galementtudi la possibilit dun effet secondaire : lacontamination des traches de lacarien parles particules de sucre.Le sucre utilis tait constitu de pur saccha-rose blanc finement broy dont les particulesmesuraient en moyenne de 2540 m m(Fig. 1). Le saupoudrage a t fait soit manuel-lement soit laide dun appareil soufflant delair sur des abeilles ayant ou non t aupa-ravant anesthsies au CO2. Des chantillonsde 49 107 abeilles (moyenne 78) ont tprlevs dans 6 colonies et cinq rptitionsont t faites pour chacun des sept traite-ments : (A) saupoudrage direct de 5 g desucre de ptissier, (B) saupoudrage de 0,5 gde sucre laide dun appareil souffleursimple (Fakhimzadeh, 2000), (CA) anes-thsie des abeilles au CO2 puis traitementA, (CB) anesthsie au CO2 puis traitementB, (C) anesthsie au CO2 seulement, (D1)tmoin secou comportant des chantillonsdoucement rouls et secous comme danstous les traitements prcdents, (D2) traite-ment tmoin dans lequel les abeilles ne sontni secoues ni roules. Au total 252 acariensont t suivis et les rsultats ont t analysspar des tests G.Une autre exprience a t faite avec troiscolonies ayant un faible taux dinfestation(2,5 acariens/100 abeilles) et quatre rpti-tions ont t faites pour chacun des cinq trai-tements suivants : A, B, CA et D2 comme ci-dessus, C3A tait semblable CA mais avecune plus longue exposition des abeilles auCO2 (3 min). Les premiers stigmates thora-ciques (T2) et les conduits des traches cor-respondants ont t dissqus et la prsencede particules de sucre a t examine aumicroscope lectronique balayage.Rouler ou secouer les abeilles avec ou sansanesthsie na pas provoqu une chute

Sugar dusting as a control method of Varroa destructor mites 145

significative des acariens. Lanesthsie auCO2 na pas affect significativement lachute des acariens rsultant du saupoudragede sucre (P = 0,893 ; Tab. I) ; en cons-quence les traitements avec ou sans anes-thsie ont t regroups pour comparer lestraitements de saupoudrage. Le saupoudragedirect de 5 g de sucre a provoqu la chute de91 % des acariens contre 62 % pour le sau-poudrage de 0,5 g de sucre avec le souffleur(diffrence significative P = 0,001). Le sau-poudrage a agi rapidement puisque presquetous les acariens tombs ont t trouvs aubout de 18 h de traitement. La mortalit desabeilles a t uniforme avec une moyennede 0,5 % dans toutes les rptitions de tousles traitements sauf pour A et B o elle a tparfois 0,5 % mais a atteint dautres fois 8 26 %. La cause de la mortalit des abeillesreste inconnue puisquaucune particule desucre na t retrouve dans les conduits destraches quel que ft le traitement (n =200 traches observes). Par contre lambu-lacre de V. destructor est apparu bien recou-vert de particules aprs les saupoudrages(Fig. 2). Lefficacit du saupoudrage directde sucre (91 %) est plus lev dans cettetude que celle mentionne pour les traite-ments lamitraz ou au fluvalinate despaquets dabeilles. Il est pourtant ncessairede vrifier limpact du saupoudrage de sucresur le couvain et la reine avant dinclurecette mthode dans une stratgie de lutteintgre pour contrler V. destructor sur lesabeilles adultes.

Varroa destructor / lutte physique /saupoudrage / anesthsie / trache

Zusammenfassung Wie stark ist derAbfall von Varroa destructor von adultenHonigbienen nach Einstubung mitPuderzucker im Laborversuch. Auf Grundder saugfhigen Struktur der Haftlappen(Ambulakrum) bei Varroa destructor(Anderson and Trueman, 2000) waren ver-schiedene Staubpartikel fr eine Behand-lung getestet worden, in denen feiner

Traubenzucker, gemahlener Pollen oderWeizenmehl auf Bienen auf Waben gestubtworden war, um die Milben von den Bie-nen zu entfernen. Die Versuche waren viel-versprechend, besonders wenn keine Brutvorhanden war. In den hier dargestelltenLaborversuchen sollte die Wirksamkeit vonPuderzucker zur Milbenbekmpfung mithherer Genauigkeit bestimmt werden. Auchder Nebeneffekt, die Verunreinigung derTracheen der Bienen mit Zuckerpartikeln,wurde untersucht.Ich benutzte Puderzucker, der nach Anga-ben des Herstellers aus fein gemahlener Sac-charose mit Krnergr b en von 2540 m mbestand (Abb. 1). Das Einstuben erfolgtedirekt oder wurde mit einem Haarfhn ver-strkt, mit oder ohne vorherige Narkotisie-rung durch CO2. Proben mit 49 bis 107 Bie-nen (M = 78) wurden aus 6 Vlkerngenommen und jeweils folgenden Behand-lungen unterzogen: (A) direktes Einstuben mit 5 g Puderzuk-ker, (B) Einstubung mit 0,5 g Puderzuckermit Untersttzung durch einen Fhn(Fakhimzeh 2000), (CA) Methode A mitCO2 Narkose, (CB) Methode B mit CO2 Narkose, (C) nur eine CO2 Narkose, (D1)Kontrollprobe mit Bienen, die sanft gerolltund geschttelt werden wie in vorherigenBehandlungen, (D2) Kontrolle ohne Scht-teln und Rollen der Bienen. Alle Versuche wurden 5 mal wiederholt.Insgesamt wurden 252 Milben verfolgt, unddie Ergebnisse des Abfallens wurde mitG Tests analysiert. In einem anderen Versuch (4 Wiederholun-gen) wurden Bienen von 3 gering befallenenVlkern (2,5 Milben/100 Bienen) 5 ver-schiedenen Behandlungen unterzogen: A,B, CA und D2 wie oben beschrieben, undC3A, die hnlich wie Behandlung CA war,bei der aber die Narkose lnger dauerte(3 Minuten). Die ersten Stigmen des Thorax(T2) mitsamt den Tracheenschluchen wur-den seziert und unter dem Raster Elektro-nenmikroskop auf Zuckerpartikel unter-sucht.

K. Fakhimzadeh146

Weder Rollen noch Schtteln der Bienenper se, noch die anschlie b ende CO2 Narkose fhrte zu einem signifikanten Mil-benabfall. Auch beim Einstuben mit Zuk-ker hatte die Narkose keinen signifikantenEffekt (P = 0,893, Tab. I). Deshalb wurdendiese Werte mit denen ohne Narkosezusammengefasst, um die Wirksamkeit derverschiedenen Einstaubmethoden zu ver-gleichen. Bei der direkten Einstubung mit5 g Puderzucker fielen 91 % der Milben ab,im Vergleich dazu nur 62 % nach der Ein-stubung mit 0,5 g Puderzucker, der mitHilfe des Fhns verteilt wurde. DieserUnterschied war signifikant (P = 0,001).Die Einstubung hatte eine schnelle Wir-kung, bereits nach 18 Stunden wurden fastalle abgefallenen Milben gefunden.Die Bienensterblichkeit lag gleichm b igbei einem Mittelwert von 0,5 % in allenWiederholungen aller Methoden mit Aus-nahme von den Behandlungen A und B, beidenen in einigen Versuchen ein Totenfallvon 8 % bis sogar 26 % vorkam. Die Ursa-che der hohen Mortalitt blieb unbekannt, danach keiner Behandlung eine Verunreini-gung durch Zuckerpartikel in den Tracheenfestgestellt werden konnte (200 Tracheenwurden untersucht). Die Haftlappen vonVarroa destructor waren dagegen stark mitZuckerpartikeln berzogen (Abb. 2).Die Wirksamkeit der direkten Einstubungmit Puderzucker war mit 91 % hher als diefr die Behandlungen von Paketbienengegen Varroa beschriebene Wirksamkeitvon Fluvalinat oder Amitraz. Die Wirkungder Einstubung mit Zucker auf Brut oderKniginnen muss noch genauer untersuchtwerden, bevor man diese Methode in einintegriertes Behandlungskonzept gegen Var-roa auf adulten Bienen einbeziehen kann.

Varroa destructor / Varroosis Kontrolle /Einstubung / CO2 / Tracheen

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