• John Mackay

Under the Microscope - Avoid Hive Killer 1 this Winter


The colder winter days certainly are telling us that winter will soon be here. Concerns may be high as there are a number of reports of high varroa levels being seen in many apiaries.

High varroa means the potential for high levels of Deformed Wing Virus (DWV) – or as we think it should be called, Hive Killer 1.

This is the virus that piqued our interest in bee viruses and prompted us to start looking at bee pathogens a decade ago. A paper from the UK (1) indicated that high levels of DWV were associated with overwintering losses. There’s the common mantra ‘control varroa, control the viruses’, meaning that if you kill the varroa then viruses are no issue.

Not quite that simple unfortunately – as viral levels can continue to rise in the bees even as the varroa levels reduce during treatment. Therefore, the precautionary principle should apply – if you’ve got signs of high varroa levels, assume you likely have high levels of DWV and these hives are at risk of dying overwinter.

But is that that death a bad thing?

DWV bee
Deformed wing virus is transmitted by varroa mite, but it can still be present in a hive without a high mite count says John Mackay.

Should these weaker hives be culled in order to reduce viral loads and any increasing virulence that DWV causes? As a review in 2021 said “If virulence is not punished, it will proliferate” (2), suggesting that to maintain weak colonies or combine with stronger ones was to encourage the survival and proliferation of this damaging virus.

The paper also suggests that our AFB control practices (ie culling these infected hives) is one of the most important, yet rarely seen, practices for virulence management.

Beekeepers suffer from the fact that these viruses are often named after visual symptoms. Often beekeepers will assume their hives are virus-free because ‘all the bees look fine and there are no stunted wings’. Don’t fall for it. We can often detect very high levels in bees that show no visual symptoms at all. Again, if you have, or had, high levels of varroa going into these cooler days, assume the levels of virus are higher as well.

John Mackay

1 Deformed Wing Virus Implicated in Overwintering Honeybee Colony Losses

(free: https://aem.asm.org/content/aem/75/22/7212.full.pdf)

2 Varroa destructor: A Complex Parasite, Crippling Honey Bees Worldwide.

(free: https://www.cell.com/action/showPdf?pii=S1471-4922%2820%2930101-X

John Mackay is the technical director at dnature and has a range of experience in applied science and molecular diagnostics spanning 25 years.