Honey bee colonies globally face a significant threat from the parasitic mite Varroa destructor. These mites can cause considerable damage, leading to weakened bees and eventual colony collapse if left unmanaged. Beekeepers widely use Amitraz, an effective acaricide, to control these mite populations and maintain colony health. Understanding how Amitraz works and applying it correctly are part of responsible beekeeping practices.
Understanding Varroa Mites
Varroa destructor mites are external parasites that target honey bees. These mites harm bees by feeding on their fat bodies and hemolymph, which is comparable to insect blood. This feeding weakens individual bees, reducing their lifespan and compromising their ability to perform colony functions.
Beyond direct feeding, Varroa mites transmit various viruses, including Deformed Wing Virus (DWV), Acute Bee Paralysis Virus (ABPV), and Israeli Acute Paralysis Virus (IAPV). These viruses, often innocuous on their own, become highly virulent when vectored by mites, leading to severe symptoms like deformed wings and paralysis. Uncontrolled mite infestations can suppress a bee’s immune system, making them more susceptible to pathogens and contributing to colony decline.
How Amitraz Works
Amitraz is an acaricide that targets the nervous system of Varroa mites. It functions as an octopamine receptor agonist, meaning it mimics the action of octopamine, a neurotransmitter in invertebrates. By binding to and activating these receptors, Amitraz overstimulates the mite’s nervous system, leading to paralysis and death.
Amitraz is considered safe for honey bees at recommended dosages due to differences in their nervous systems compared to mites. Specifically, the honey bee’s octopamine receptor (Octβ2R) is less sensitive to Amitraz than the mite’s receptor. This selective toxicity allows Amitraz to effectively control mite populations while minimizing harm to the bees. Amitraz primarily acts through contact, meaning mites are affected when they come into direct contact with the substance. It is effective against both phoretic mites, which are those riding on adult bees, and mites within capped brood cells, contributing to its efficacy in reducing mite populations within the hive.
Applying Amitraz Safely
Amitraz is available in several formulations for Varroa treatment, commonly as plastic strips or gels. Products like Apivar are slow-release strips designed to deliver amitraz over 42 to 56 days. Another option, Amiflex, is a faster-acting gel treatment with a 7-day duration. Beekeepers place these strips or apply the gel within the hive, often between frames in the brood area, to ensure bees contact the active ingredient and distribute it throughout the colony.
Always follow label instructions for beekeeper safety and honey purity. Beekeepers should wear personal protective equipment, such as gloves and eye protection, to prevent skin contact or inhalation. Precise dosing, placement, and adherence to recommended treatment durations are necessary. A withdrawal period is necessary before honey harvest to prevent contamination, often requiring strip removal before honey supers are added or at least 14 days prior to collection. It is also advised not to extract honey from brood chambers.
Addressing Resistance and Sustainable Use
The development of Varroa mite resistance to acaricides like Amitraz is a growing concern, often resulting from repeated or improper use. Resistance occurs through natural selection, where mites with genetic variations survive exposure and reproduce, passing on resistance. Studies have shown increasing levels of Amitraz resistance in Varroa populations in various regions, including France, the Czech Republic, the USA, and Argentina.
To mitigate resistance, beekeepers should implement integrated pest management (IPM) strategies. This involves rotating different classes of acaricides to vary the mode of action, preventing mites from developing resistance to a single compound. Regular monitoring of mite levels helps determine treatment efficacy and guides decisions on when and which treatments to apply. Incorporating non-chemical methods, such as screened bottom boards, powdered sugar dusting, essential oils (e.g., thymol), drone brood removal, or thermotherapy, diversifies the management approach and reduces reliance on chemical treatments, supporting long-term bee health.