The Advantage of Splitting for Varroa Mite Management: an IPM Approach

Thursday, 16 January 2025

To effectively manage Varroa mites, beekeepers must adapt an integrated pest management approach, which includes various chemical, physical and cultural methods. Although the use of chemicals is important, beekeepers should not underestimate the value of the many cultural and physical methods available to keep mite levels under control prior to intervening with chemical treatments. This week’s blog will focus on specific non-chemical practices beekeepers do that help manage Varroa mites within an operation.

The Advantage of Splitting for Varroa Mite Management: an IPM Approach

It is a common practice of beekeepers to split colonies of bees each spring and summer. How often, and when, beekeepers split colonies depends on the needs of their operation. Typically hives are split in May, prior to pollination, which helps beekeepers equalize colonies prior to sending them to pollination, and can provide nucleus colonies to sell or keep. Hives can also be split following pollination, in June and July, which helps beekeepers prevent colonies from swarming, and can also increase their number of colonies. What beekeepers may not think of when splitting is how this practice helps manage Varroa mites.

Newly split colony ©ATTTA

To understand why splitting helps manage Varroa mites, it helps to have a general understanding of the Varroa mite life cycle. Mites spend part of their life cycle attached to adult bees, but move into brood cells to reproduce. A female mite will enter a brood cell just before it is capped, and she will lay her eggs within the cell. Then, once the bee emerges from the cell, any mature female mites will leave the cell to continue the life cycle. What this means is that the presence of brood is essential for mites to reproduce and grow their population. If there is a break in brood production, such as when a beekeeper splits a colony, this also creates a break in mite reproduction.

Splitting a colony creates a break in the honey bee brood cycle, but this break will differ in length depending on how the beekeeper chooses to make the split. The longest break resulting from a split is what beekeepers call a “walk away” or “queenless” split, which is when the beekeepers leaves the bees to make their own queens. From the day the colony is split, it will take approximately 14 days for a new queen to be made and emerged into a colony. It will take 5-7 days before the queen takes her orientation flight and mating flight. It will then take another 5-7 days before she starts to lay eggs, and workers will not emerge from the cell until 21 days after that. This means no new brood will emerge for at least 43 days after the split was done. It is important to understand that mite reproduction can resume once the queen starts laying eggs. So the 43 days to new brood emergence in walk away splits may only include a 22-day break in mite reproduction, which can significantly reduce population growth.

Another option beekeepers may choose when making splits is introducing queen cells. This option provides a shorter break in the brood cycle than a “walk away” or “queenless” split, but still provides a benefit of slowing mite reproduction. When a queen cell is introduced to a newly made split, the queen will emerge within the next 3-4 days depending on what day the cell was harvested and how long it was incubated. This means no new brood will emerge for approximately 33 days after the split was done, and provides an approximate 12-day break in mite reproduction.

Finally, beekeepers may choose to introduce a mated queen into their newly made split. This provides a much shorter break in the brood cycle as the queen will start to lay eggs shortly after being introduced into the colony, which allows mites to quickly resume reproducing.

Splitting colonies is something beekeepers do regularly, and it is an added advantage that it slows mite population growth. Beekeepers should consider the fact that making splits can be part of their integrated pest management approach to managing Varroa. Beekeepers should remember to monitor for Varroa mites each month during the beekeeping season to assess if their integrated pest management plan is working. Finally, there are other cultural and physical methods of managing Varroa mites, which will be explored in future blogs.

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