A laboratory bioassay was developed to evaluate miticides to control Varroa jacobsoni (Oudemans), an important parasite of the honey bee, Apis mellifera L. Bees and mites were exposed to applications of essential oil constituents in petri dishes (60 by 20 mm). The registered mite control agents tau-fluvalinate (Apistan) and formic acid also were evaluated as positive controls. Treatments that caused high mite mortality (> 70%) at doses that produced low bee mortality (< 30%) were considered mite selective. The six most selective of the 22 treatments tested (clove oil, benzyl acetate, thymol, carvacrol, methyl salicylate, and Magic3) were further evaluated to estimate LD50 values and selectivity ratios (A. mellifera LD50/V. jacobsoni LD50) at 24, 43, and 67 h after exposure. Tau-fluvalinate was the most selective treatment, but thymol, clove oil, Magic3, and methyl salicylate demonstrated selectivity equal to or greater than formic acid. The effect of mode of application (complete exposure versus vapor only) on bee and mite mortality was assessed for thymol, clove oil, and Magic3 by using a 2-chambered dish design. Estimated V. jacobsoni LD50 values were significantly lower for complete exposure applications of thymol and Magic3, suggesting that both vapor and topical exposure influenced mite mortality, whereas estimated values for clove oil suggested that topical exposure had little or no influence on mite mortality. These results indicate that essential oil constituents alone may not be selective enough to control Varroa under all conditions, but could be a useful component of an integrated pest management approach to parasitic mite management in honey bee colonies.

https://bioone.org/journals/Journal-of-Economic-Entomology/volume-93/issue-2/0022-0493-93.2.189/Laboratory-Evaluation-of-Miticides-to-Control-Varroa-jacobsoni-Acari/10.1603/0022-0493-93.2.189.pdf

Laboratory evaluation of miticides to control Varroa jacobsoni (Acari: Varroidae), a honey bee (Hymenoptera: Apidae) parasite.

Laboratory bioassays to assess the pathogenicity of mitosporic fungi to Varroa destructor (Acari: Mesostigmata), an ectoparasitic mite of the honeybee, Apis mellifera

The potential for Metarhizium anisopliae (Metschinkoff) to control the parasitic mite, Varroa destructor (Anderson and Trueman) in honey bee colonies was evaluated in field trials against the miticide, tau-fluvalinate (Apistan). Peak mortality of V. destructor occurred 3–4 d after the conidia were applied; however, the mites were still infected 42 d posttreatments. Two application methods were tested: dusts and strips coated with the fungal conidia, and both methods resulted in successful control of mite populations. The fungal treatments were as effective as the Apistan, at the end of the 42-d period of the experiment. The data suggested that optimum mite control could be achieved when no brood is being produced, or when brood production is low, such as in the early spring or late fall. M. anisopliae was harmless to the honey bees (adult bees, or brood) and colony development was not affected. Mite mortality was highly correlated with mycosis in dead mites collected from sticky traps, indicating that the fungus was infecting and killing the mites. Because workers and drones drift between hives, the adult bees were able to spread the fungus between honey bee colonies in the apiary, a situation that could be beneficial to beekeepers.

Field trials using the fungal pathogen, Metarhizium anisopliae (Deuteromycetes: Hyphomycetes) to control the ectoparasitic mite, Varroa destructor (Acari: Varroidae) in honey bee, Apis mellifera (Hymenoptera: Apidae) colonies.

Three oxalic acid (OA) solutions were applied to 24 honeybee colonies to test acaricidal effects on Varroa destructor. Daily natural mite drop per colony averaged 0.52. Higher mite mortality (18.33) was found after three August OA treatments. The mean efficacy's of the three water solutions of OA/sucrose (w/w), 3.4%/47.6%, 3.7%/26.1%, and 2.9%/31.9% applied in the presence of brood, was 52.28%, 40.66% and 39.16% respectively. A significantly higher efficacy was recorded when 3.4%/47.6% was applied in comparison to 2.9%/31.9% solution. There was no difference in effi- cacy between OA solutions administered during a broodless period on October 28. The average effi- cacy in all colonies was 99.44%. The results suggest that OA has limited acaricidal effect in colonies with brood, but it is highly effective in a broodless period. Varroa destructor (jacobsoni) / honeybee / control / oxalic acid /efficacy

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Acaricidal effect of oxalic acid in honeybee (Apis mellifera) colonies

Trois methodes d'echantillonnage pour estimer la taille des populations de l'acarien Varroa destructor ont ete comparees sur deux ans dans 22 colonies d'abeilles domestiques (Apis mellifera) : (1) destruction parle fluvalinate de tous les acariens presents dans la colonie. On a considere que le nombre total d'acariens morts recoltes durant six semaines consecutives equivalait a la population d'acariens de la colonie avant le traitement (2) estimation de la population d'acariens par echantillonnage d'abeilles immatures (200 cellules de couvain d'ouvrieres opercule et toutes les cellules de mâles operculees) et d'adultes (n = 200). On a estime le nombre total d'abeilles immatures et adultes pour calculer le nombre total d'acariens dans la colonie ; et (3) echantillonnage de la mortalite naturelle de la population d'acariens en denombrant chaque semaine les acariens trouves morts sur un plateau de fond « anti-varroas ». Les methodes 2 et 3 ont ete en outre appliquees a six colonies choisies au hasard lors de cinq echantillonnages supplementaires. Les trois methodes ont ete comparees deux a deux par une analyse de regression. Il y a eu une bonne relation lineaire entre le nombre d'acariens morts naturellement chaque semaine et la population absolue estimee par les infestations des nymphes et des adultes (r 2 = 0,835) (Fig. 1 ). Les donnees sur les acariens morts naturellement chaque semaine (D m ) ont ete comparees avec le nombre total d'acariens tues par traitement chimique (Fig. 2). La regression donne une equation qui transforme D m en population absolue d'acariens (M): Log (D m ) = 2,818 + 1,035 log (M). Le modele a une bonne adequation avec les donnees (r 2 = 0,915) et de bonnes performances de prediction (R 2 prediction = 0,901). Le coefficient de correlation des concordances confirme la bonne reproductibilite des deux methodes (r c = 0,932). Enfin, le nombre total d'acariens tues par traitement chimique a ete compare a la population absolue d'acariens estimee d'apres les niveaux d'infestation des abeilles adultes et des cellules de couvain echantillonnees juste avant le traitement chimique (Fig. 3). La premiere annee tout particulierement, le coefficient de correlation (r = 0,983) et le coefficient de correlation des concordances (r c = 0,933) montrent tous deux que ces deux variables sont semblables. Nous en concluons qu'estimer la population absolue d'acariens par les infestations des abeilles peut etre une methode tres precise si l'on utilise a la fois des echantillons de couvain et d'abeilles adultes. La methode necessite neanmoins un trop gros travail de terrain et de laboratoire pour estimer simultanement les niveaux d'infestation des adultes et des cellules de couvain et le nombre d'abeilles dans la colonie. En outre elle est destructive et ne peut donc pas etre repetee. Par contre, l'echantillonnage des acariens morts naturellement constitue une facon aisee d'estimer la population d'acariens sans interferer avec la colonie ou l'acarien lui-meme. Dans cette etude il y a eu une bonne correlation entre le nombre d'acariens morts naturellement et la population absolue estimee par les deux autres methodes. Mais la methode n'a ete valable que pour les colonies qui ont du couvain et ne s'effondrent pas a cause de la varroose. Il faut aussi cumuler le nombre d'acariens morts sur une semaine au moins.

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A comparative evaluation of sampling methods for Varroa destructor (Acari: Varroidae) population estimation

SUMMARYThe effectiveness of two acaricides, fluvalinate and flumethrin, against Varroa jacobsoni was tested in field colonies of honey bees containing sealed brood.The experiment was carried out with three groups of five hives containing Apis mellifera mellifera. One group was treated with a polyvinyl chloride (PVC) strip containing 0.8 g of fluvalinate. A second group received two polyethylene strips each containing 3.6 mg of flumethrin. The third group served as a control and received no treatment. Treatment strips remained in hives for 28 days.Infestation rates in adult bees and brood were measured before and after the treatment, and the effectiveness was calculated as a percentage of the initial infestation. The effectiveness was higher than 95% for both acaricides, whereas the infestation rate increased in the control group.

Comparative tests of fluvalinate and flumethrin to control Varroa jacobsoni Oudemans

SUMMARYThe effectiveness of half the recommended dose of fluvalinate (Apistan) and flumethrin (Bayvarol) against Varroa jacobsoni was tested in honey bee colonies containing sealed brood. The experiment was carried out in Zaragoza, Spain, in five apiaries of 15 hives each, containing colonies of Apis mellifera mellifera. Each apiary was divided into three groups. Hives in one group were each treated with a polyvinyl chloride (PVC) strip containing 0.8 g of fluvalinate. Hives in the second group each received two polyethylene strips each containing 3.6 mg of flumethrin. The third group served as a control and received no treatment. Treatment strips were left in the hives for 28 days. Varroa infestation rates were measured in adult bees and sealed brood before and after the treatment. Both of the tested acaricides reduced the infestation rate to practically zero in both adult bee and sealed brood Infestations. Infestation rates in the two groups of treated colonies were significantly different from those in...

C. Sanchez-Acedo

Papers

Comparative tests of fluvalinate and flumethrin to control Varroa jacobsoni Oudemans

Field trials of treatments against Varroa jacobsoni using fluvalinate and flumethrin strips in honey bee colonies containing sealed brood