In the context of acaricidal treatments, it is common practice among beekeepers to rely on the guidance of fellow apiarists when selecting products and application methods. However, it is equally frequent to observe variations in outcomes from identical treatment protocols1. What accounts for this discrepancy?
The range of registered acaricides for controlling Varroa destructor is relatively limited, and significant differences exist among these products. For example, looking at the origin of the active ingredient 2 we classified them as:
The pharmacokinetics of these treatments, which describe how a drug is absorbed, distributed, and eliminated within the colony, also play a crucial role. The distribution and elimination phases define the classification as long or flash treatment.According to this process we can draw two groups of varroa management treatment:
So far, most flash treatments have been relying on contact with organic acids like oxalic or formic acid. However, there are now also available in some countries fast-acting amitraz-based treatments (e.g., Amiflex®). Each method has its optimal application, along with specific advantages and disadvantages that beekeepers should be aware of 6,7.
While all treatments are more effective with smaller amounts of brood, this is particularly crucial for certain flash treatments. For example, oxalic acid should be used during broodless periods, such as natural brood breaks in winter, colony splitting, or when the beekeeper has forced a brood break as part of an integrated control program (for instance by caging the queen) 8,9. This broodless condition is mandatory for oxalic acid to achieve the desired effectiveness. In contrast, amitraz can still achieve a high efficacy even in presence of brood (providing that the strips are left long enough in the colony), making it a more versatile option for beekeepers.
In countries such as Italy and France, it is common practice to confine the queen (caging or ringing) for a duration of 24 to 28 days. Following this period, the absence of brood allows for the application of oxalic acid, which has demonstrated high efficacy under these specific conditions 7,10. This method not only proves effective but also ensures that no residual contaminants remain in the wax, making it suitable for organic/natural production 6. However, queen caging is not advisable during the spring months due to the potential for swarming and the possibility that significant nectar flows could obstruct the brood frames. Consequently, the combined approach of queen caging and oxalic acid treatment is best utilized during the summer or early autumn months. 9
In warmer regions characterized by dry summers, such as the Mediterranean basin or California, there is a natural decline in egg-laying due to the discontinuance of flowering. This period presents an optimal opportunity for the application of fast-acting treatments. Furthermore, these treatments can also be effectively employed in the spring on newly established swarms, capitalizing on the absence of brood during the queen’s renewal phase or prior to the commencement of her laying activities6,8.
Slow-release treatments exhibit enhanced efficacy in conditions characterized by lower brood levels; however, their prolonged action permits application even when reducing brood is neither feasible nor advisable, such as during the autumn months. These treatments function by targeting varroa mites that emerge alongside the bees over multiple brood cycles, thereby maximizing their overall impact on the mite population within the hive 7,8. Nonetheless, the extended contact with brood frames increases the risk of leaving chemical residues in the wax, a concern that varies depending on the specific treatment employed 6.
The implementation of these therapeutic methods requires minimal time investment. The primary maintenance task involves scraping the surfaces of treatment strips when they become coated with propolis to prevent resin from obstructing the release of the active ingredient. For optimal effectiveness, it is essential that the hive is adequately populated; without sufficient bee movement and interaction with the treatment strips, the efficacy of the treatment may be compromised9.
Although synthetic treatments, such as amitraz, have proven highly effective in managing varroosis, it is crucial to use these compounds judiciously while adhering to the summary of product characteristics (SPC) to mitigate the development of resistance and prolong the effectiveness of these treatments 6,10.
Flash treatments like Amiflex can be a valuable tool for achieving a rapid knock-down of varroa mite populations. These treatments provide quick and effective results, making them particularly useful in situations where immediate action is required. However, it is important to recognize that both flash treatments and conventional slow-release treatments have their respective roles and benefits. Combining these methods strategically throughout the beekeeping season can optimize mite control efforts. Flash treatments can be employed before, between, or after honey flows to quickly reduce mite levels, while conventional treatments can offer sustained protection over longer periods (particularly as an end-of-season treatment). By integrating both approaches, beekeepers can address different infestation levels and environmental conditions, ensuring comprehensive varroa mite management.
Furthermore, the maintenance of optimal hive health necessitates the development and implementation of a comprehensive, season-long management strategy. It is highly advisable for beekeepers to seek consultation with apiary inspectors and veterinary professionals, particularly when uncertainties arise regarding treatment efficacy, timing, selection, or application methodologies 11,12. A thorough comprehension of the distinctions between various therapeutic interventions will not only enhance beekeepers’ health management practices but also foster increased confidence in their treatment regimens 13,14.
The judicious application of best management practices, including proper nutrition, disease prevention, and strategic treatment protocols, is paramount for sustaining colony vigor and productivity 11,15. Furthermore, staying abreast of the latest research findings and evolving management techniques is crucial for adapting to the dynamic challenges faced by honey bee populations12,14.
By adopting a holistic approach to hive management, integrating scientific knowledge with practical experience, beekeepers can significantly contribute to the long-term health and sustainability of their colonies, thereby supporting both apicultural interests and broader ecosystem services 13,15.
References:
by Gérald Therville Table of contents Varroosis, caused by Varroa destructor, is a major challenge to honey bee colonies (Apis mellifera). Even with the development and successful implementation of various management strategies to
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