Managing Varroa A Holistic Approach

Varroa mites (Varroa destructor) are one of the biggest threats to honeybee colonies. If left unmanaged, these parasites can devastate a hive within 18 months, likely much sooner. For new beekeepers or newbees, deciding how to combat varroa can feel overwhelming. Here are some insights into managing varroa mites, covering chemical and non-chemical treatments and monitoring methods. It is better to use tried-and-tested methods before experimenting with other riskier, less invasive techniques. Do not experiment on all of your hives or you risk losing them all. Like other bee pests and diseases, your management affects other beekeepers; poorly managed varroa can spread to nearby apiaries, sometimes known as a “varroa bomb”.  

It’s not the varroa that kill the bees, it’s the viruses that they carry and the reduction in immunity to these diseases. 

Understanding Varroa Management  

Remember, chemicals, especially synthetic, effectively kill mites but they will also impact your bees, especially the queen, and leave residues in wax or honey. 

Varroa feed on the fat body cells of bees, not only weakening them but transmitting diseases like Deformed Wing Virus (DWV). Their lifecycle is entwined with that of the bee, so understanding both will help you to treat the mites more efficiently. Auckland, in the warmer sub-tropical north, there tends to be brood present throughout winter, allowing mites to reproduce continuously. While further south, brood breaks allow for easier varroa eradication.  

Chemical Treatments  

Chemical treatments for mites, also known as miticides, are usually necessary for the beginner, particularly during heavy infestations. These chemicals can be harmful to beekeepers, consumers, bees and the environment; they should be used with care, carefully following manufacturers recommendations. Miticides vary in their effectiveness, convenience, and impact on bee health. When using chemicals to control varroa we want all the mites killed and none of our bees harmed. Synthetic chemicals tend to be considerably more toxic to mites than bees; up to a thousand times more toxic. Essential oils can be only a few times more toxic to mites than bees. Consider also that instant death is not the only way that bees and their hive may be harmed. 

The poison is in the dose ("All things are poison, and nothing is without poison; only the dose makes a thing not a poison." Paracelsus, a 16th-century physician and alchemist) 

Chemical Resistance 

Resistance to chemical treatments are a serious issue for bees and beekeepers. We are already seeing resistance to some synthetic chemicals, most likely to improper use.  

It is like an arms race between mites and our treatments, mites evolve resistance to miticides and then we make other miticides which they will evolve resistance to eventually. It’s not static, the battle is escalating which leads many to see chemicals as a means to gain us time to find other ways to combat mites like breeding varroa resistant bees. It’s unlikely that our management strategy will be using strips every spring and autumn in ten years’ time. We’re into our third decade of varroa infestation and every year is different, you cannot be complacent, continuing to up your game with varroa control. 

The best way to slow down or reduce resistance to synthetic treatments is to alternate treatments. 

Bear in mind that some treatments are from the same chemical family; Bayvarol uses Flumethrin and Apistan uses Fluvinate, both chemicals are Pyrethroids and shouldn’t be used consecutively e.g. if you use Bayvarol in the spring, then you could use Apitraz in the autumn. 

Chemical resistance has not been observed in organic miticide treatments.