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International audience; Young honey bee larvae were transferred into the queen cups containing known concentrations (0 to 1000 mg/kg) of the organophosphate pesticide coumaphos. These larvae were placed in queenless colonies and examined ten days later to determine the rate of rejection or acceptance as indicated by a mature sealed queen cell. All queens failed to develop at 1000 mg/kg, and greater than 50% of the queen cells were rejected at the 100 mg/kg concentration. Additionally, queens that survived exposure to100 mg/kg coumaphos weighed significantly less than control queens. The implications of exposure of developing queens to sublethal amounts of pesticides are discussed.

The ability of the parasitic mite Varroa destructor to transmit Kashmir bee virus (KBV) to the Western honey bee (Apis mellifera) was investigated by exposing pupae from a KBV-negative colony to varying numbers of adult female mites from KBV-positive colonies. After five days, the virus status of pupae and the mites was determined by RT-PCR. There was a significant relationship between KBV- positive pupae and exposure to KBV-positive mites. No pupae were virus-positive when all the mites introduced into a given cell subsequently tested negative. Mites testing positive for KBV transmitted virus about 70% of the time. The percentage of KBV-positive V. destructor in a given cell also increased significantly, suggesting virus-free mites became virus-positive by cohabiting in the same cell with virus- positive mites, and we calculated the mite-to-mite transmission rate as 51%. There was 100% sequence identity of 415 bp KBV fragment amplified from bee pupae and mites, reflecting two isolates of the same virus source and supporting the conclusion of virus transmission from mite to bee pupae. Kashmir bee virus / transmission / Varroa destructor / RT-PCR

Since resistance of the causative organism of American foulbrood, Paenibacillus larvae subsp. larvae, to oxytetracycline (OTC) is becoming widespread in the United States, we began a search for effective alternative antibiotics. We investigated the sensitivity of P. l. larvae to 27 antibiotics, which were primarily ones already registered with the US Food and Drug Administration for agricultural uses. Bacterial resistance to OTC also conferred resistance to other tetracyclines, although the level of resistance varied. The most active antibiotics screened that are currently used in agriculture were erythromycin, lincomycin, monensin, and tylosin. Rifampicin was by far the most active antibiotic tested, but since it is used against tuberculosis, registration of this material for agricultural use is unlikely. Apis mellifera / Paenibacillus larvae larvae / antibiotic / resistance / American foulbrood

International audience; The antibiotic lincomycin hydrochloride was evaluated for toxicity to larval and adult honey bees and for efficacy in controlling American foulbrood disease (AFB). Results of toxicity studies involving nine applications of lincomycin (200-, 600-, or 1000 mg active ingredient per application) as a dust in confectioners sugar revealed no significant differences in mortality among any of the treatment groups for either adults or larvae, when compared to untreated or sugar-treated controls. In field efficacy studies, 18 colonies with existing oxytetracycline-resistant AFB were dusted three times, one week apart, with either 100-, 200-, or 400 mg lincomycin (in 20 g confectioners sugar). Forty- five days after the third treatment, no visible signs of AFB could be found, regardless of the initial severity of disease or the dose applied.

On a montre que des extraits a l'ethanol de spores et de myceliums d'Ascosphaera apis, champignon responsable du couvain plâtre chez les larves d'abeilles (Apis mellifera L), renfermaient un agent antimicrobien qui inhibait la bacterie Bacillus larvae, agent de la loque americaine. Le champignon a d'abord etait multiplie au laboratoire sur un bouillon de dextrose de pomme de terre (additionne d'un extrait de levure a 4 mg/ml) a 30 °C. Puis on a procede a une serie de fractionnements a l'aide de solvants (a) melange d'une solution aqueuse de methanol a 70% et de n-hexane et b) melange de n-butanol et d'eau) et de chromatographies sur colonne (C 18 suivi par du gel de silice) pour purifier les composes antimicrobiens

L'activite antibiotique de l'acide linoleique contre la bacterie responsable de la loque americaine chez les abeilles nous a conduit a examiner l'activite antimicrobienne d'autres acides gras libres satures et insatures. Le test biologique a consiste a exposer des spores de Bacillus larvae a des disques de papier traites avec 250 μg des composes etudies et a mesurer la zone d'inhibition de croissance au bout de 3 j (tableau I). Il en ressort que l'activite antimicrobienne des acides gras satures augmente avec la longueur de la chaine jusqu'a 12 carbones (acide laurique). Les acides gras satures dont la chaine contient plus de 14 carbones sont inactifs. L'activite peut etre accrue, ou restauree chez les composes qui ont les plus grandes longueurs de chaine, en ajoutant une ou plusieurs doubles liaisons