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  • Writer's picturePatrick Dawkins

No Rest from the Wicked

INSIDE PYRAMID APIARIES

Inside Pyramid Apiaries is a monthly insight into operations at Marlborough commercial beekeeping business Pyramid Apiaries. This month – varroa control, even in winter.

Like honey, the strong wool price is in the doldrums, so using a bit to help block hives during oxalic acid vaporising is a cost-effective approach for Pyramid Apiaries.

In June you could have found me in a variety of places: in the office working on Apiarist’s Advocate, vineyards earning some paycheques outside of the beekeeping world, the shed banging away at repairs and maintenance on beekeeping equipment, and – although we aim for a three-month break from cracking the lids on the beehives – out in the apiaries. Such is the constant threat of varroa.

Varroa mite has been becoming an increasing detriment to hive health in recent years all around New Zealand. Our spot in Marlborough is no different. Wherever I go it is one of the first things, if not the first, discussed with other beekeepers. The Pyramid Apiaries management plan to reduce the impact of the mites on hive health is ever changing, as we haven’t settled on the perfect plan just yet (if such a thing exists).

Like many beekeepers these days, our current iteration of the plan involves using oxalic acid treatments to supplement the frontline synthetic miticide treatments in spring and autumn. In June and July that means a quick trip around some of the more high-risk apiaries to give a blast with an oxalic acid “vaporiser”.

-2grams of oxalic acid per hive is all it takes for a vapour treatment to knockdown phoretic varroa.

Full instructions on the various methods of oxalic acid application to beehives can be found in the Control of Varroa: A Guide for New Zealand Beekeepers book by Goodwin and Taylor, but basically a quick blast (about 30 seconds to a minute) with the gun set to 230°c into the hive will sublimate the 1-2gm of acid crystals, turning them into a vapour which spreads throughout the hive.

We don’t tend to use this method any other time of the year, although many do. Now though, with June and July being the coldest months, there is the least amount of brood in the hives and thus a greater proportion of mites living in the colony will be in their phoretic stage, i.e living externally on the bees rather than under the brood cap. Although there is some evidence the vapour leaves oxalic crystals inside the hive which can kill off emerging bees in the days immediately post-treatment, it is most effective as a knock down on phoretic mites. We also have entrance reducers on our hives over winter, which makes blocking up the remainder of the gap around the vaporiser gun a faster process than in season (some beekeepers have holes drilled out of brood boxes to poke the gun into, but we just go through the main entrance).

A dozen Pyramid Apiaries hives – only about 30 minutes work with an oxalic acid vaporiser as a winter varroa treatment.

We don’t use vaporisation on all our hives. The mating units tend to have lower mite counts due to regular brood breaks throughout the season, so they avoid the ‘gun’, although close monitoring of mite levels is undertaken so we are not caught off-guard. Hives at higher altitudes which get a good brood break over winter are also less susceptible to varroa and so can thrive without the winter oxalic vapour ‘blast’. The hives most susceptible to the mites? Those lower down the valleys in warmer climes where the queen continues to lay. These hives are hard-workers too, having been stimulated (via early-spring sugar syrup feeding) into a long laying season and thus longer for varroa to build up in the season prior.

Why the long laying season? Those girls have to get to work early for the cherry pollination season which begins in September. Something we will be into, and writing about, before we know it…


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