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The ectoparasitic mite Varroa destructor Anderson & Trueman is a major pest of the honey bee Apis mellifera L. (Hymenoptera: Apidae) and its control is one of the most important challenges that beekeepers have to face. In this study, we investigated the use of the predatory mite Stratiolaelaps scimitus (Womersley) for the biological control of varroa mites in Eastern Canada, as part of an integrated pest management strategy. Our study aimed to evaluate the effectiveness of S. scimitus in controlling varroa populations in early and late fall in comparison with untreated colonies and two currently used organic treatments: Thymovar and oxalic acid. Performing weekly mite drop monitoring, we first compared the effectiveness of two introduction rates of S. scimitus (≈6,250 or 12,500 mites/colony) during a fall treatment (September) and, as we detected no differences of effectiveness between these two treatment types, we used the dosage currently recommended by biocontrol suppliers (≈6,250 mites) in a complementary treatment test (November). Results showed that S. scimitus did not succeed in controlling varroa populations in honey bee colonies when introduced either in early or in late fall according to current suppliers’ recommended rates and application method. On the other hand, our results demonstrated that Thymovar and oxalic acid remain effective options for controlling varroa mite populations during fall in Quebec, Canada.

The biocontrol of the honey bee ectoparasite Varroa destructor is an underexploited but promising avenue that would benefit from being integrated in a Varroa management program. Our study aimed to investigate the potential of the predatory mite Stratiolaelaps scimitus to control Varroa infestations in honey bees. Tests on safety and predation were carried out to: (1) assess the risk of predation of the honey bee brood by S. scimitus under laboratory conditions and within the colony, and (2) evaluate the predation potential of S. scimitus on phoretic Varroa mites. Under laboratory conditions, S. scimitus was able to feed upon free Varroa mites, but also attacked every unprotected honey bee brood stages with a strong preference for bee eggs. When introduced inside colonies, however, S. scimitus does not have negative effects on the survival of the bee brood. Moreover, observations made in the laboratory revealed that S. scimitus does not attack Varroa mites when they are attached to the body of bees. However, all Varroa mites that had naturally fallen from the bees were predated upon by S. scimitus and died in less than 24h. This study provides evidence that S. scimitus does not represent a significant threat to the bee brood, but also suggests that its effect in Varroa control will probably be limited as it does not attack phoretic Varroa mites. Our results represent a first step in assessing the potential of S. scimitus to control V. destructor and provide novel information about the predator’s behavior inside the honey bee colony.

The ectoparasitic mite Varroa destructor Anderson & Trueman is a major pest of the honey bee Apis mellifera L. (Hymenoptera: Apidae) and its control is one of the most important challenges that beekeepers have to face. In this study, we investigated the use of the predatory mite Stratiolaelaps scimitus (Womersley) for the biological control of varroa mites in Eastern Canada, as part of an integrated pest management strategy. Our study aimed to evaluate the effectiveness of S. scimitus in controlling varroa populations in early and late fall in comparison with untreated colonies and two currently used organic treatments: Thymovar and oxalic acid. Performing weekly mite drop monitoring, we first compared the effectiveness of two introduction rates of S. scimitus (≈6,250 or 12,500 mites/colony) during a fall treatment (September) and, as we detected no differences of effectiveness between these two treatment types, we used the dosage currently recommended by biocontrol suppliers (≈6,250 mites) in a complementary treatment test (November). Results showed that S. scimitus did not succeed in controlling varroa populations in honey bee colonies when introduced either in early or in late fall according to current suppliers’ recommended rates and application method. On the other hand, our results demonstrated that Thymovar and oxalic acid remain effective options for controlling varroa mite populations during fall in Quebec, Canada.

The biocontrol of the honey bee ectoparasite Varroa destructor is an underexploited but promising avenue that would benefit from being integrated in a Varroa management program. Our study aimed to investigate the potential of the predatory mite Stratiolaelaps scimitus to control Varroa infestations in honey bees. Tests on safety and predation were carried out to: (1) assess the risk of predation of the honey bee brood by S. scimitus under laboratory conditions and within the colony, and (2) evaluate the predation potential of S. scimitus on phoretic Varroa mites. Under laboratory conditions, S. scimitus was able to feed upon free Varroa mites, but also attacked every unprotected honey bee brood stages with a strong preference for bee eggs. When introduced inside colonies, however, S. scimitus does not have negative effects on the survival of the bee brood. Moreover, observations made in the laboratory revealed that S. scimitus does not attack Varroa mites when they are attached to the body of bees. However, all Varroa mites that had naturally fallen from the bees were predated upon by S. scimitus and died in less than 24h. This study provides evidence that S. scimitus does not represent a significant threat to the bee brood, but also suggests that its effect in Varroa control will probably be limited as it does not attack phoretic Varroa mites. Our results represent a first step in assessing the potential of S. scimitus to control V. destructor and provide novel information about the predator’s behavior inside the honey bee colony.