Varroa Diaries: Damage Likely Lessened This Autumn

This time last year beehives were dying in much larger numbers than usual in several North Island regions, and the recent release of Landcare Research’s NZ Colony Loss Survey pointed the figure squarely at varroa. A year later, we check in with some experienced and connected beekeepers in the Hawke’s Bay, Bay of Plenty and Waikato to get a feel for if the colony damage is being repeated this season.

Colony Loss survey findings.

“Much lower”, “a lot better” and “I haven’t heard anyone screaming out like they did last year” are the reports on varroa mite from commercial beekeepers Jane Lorimer, Russell Berry and Dennis Crowley, among others, across the North Island.

Although impossible to confirm why hive losses and mite numbers are appearing lower this season beekeepers are happy at the fact. However, there are still reports of some apiarists getting caught out, particularly with varroa, as bee forage dwindles and queens continue to lay. The concerns are certainly not on the same scale as 12 months ago though.

While at the time many of the colony losses were thought to be unexplained, discussion has since pointed the finger at heavy varroa mite loadings in hives that had spent time in areas of high hive populations. Kiwifruit pollination areas were thought to be particularly problematic.

NZ Colony Loss Survey results, from data gathered last spring, were released in March and respondents identified varroa as the leading cause of hive deaths. It dived deeper into the management of varroa and found that either treating at the wrong time, or hives suffering from reinvasion, was attributed as the main reason for colony death due to varroa in 60% of cases.

Unsurprisingly the middle North Island, where anecdotal evidence suggested greater autumn losses occurred, also suffered the most winter losses according to Landcare Research’s more scientific survey. The area, which includes Waikato, Bay of Plenty, the East Coast and Hawke’s Bay had a loss rate of 18.7%, as compared to the national average of 13.6%.

With bees seemingly healthier in those key areas this autumn, putting a finger on the reason for that improvement is difficult and unscientific. However, the seasonal conditions providing better late season forage and thus stronger bees overall to combat varroa is being mentioned.

“This year beekeepers have had to work to get hives up to the grade, but since Christmas there has been better forage,” Crowley says of the conditions he has seen in the Te Puke area.

“Weather conditions play a part in it,” says Berry, whose Arataki Honey is based in the Hawke’s Bay, but whose hives cover large areas of the middle North Island.

“Perhaps with beekeepers going broke last year, maybe there is not quite so many around not treating for varroa.”

Lorimer, a long time Waikato beekeeper, floats that idea too.

“It could be that some people have lost hives and not come back in to it, meaning those who have been beekeeping for longer have been able to get their levels under control,” she says.

The Colony Loss Survey estimates that 2.4% of beekeepers don’t treat for varroa.

With beekeepers noticing higher mite loadings last autumn, extra winter treatments might have gone into surviving colonies of more vigilant beekeepers, thus reducing levels of the external parasite, some suggest.

As is often the case, views on miticide resistance differ, but it is another reason floated for why beekeepers were caught out last autumn. However, the Colony Loss Survey had it at the forefront for only 8.1% of beekeepers whereas “ineffective dosage” was at 18.7%, signalling that some beekeepers might be the masters of their own doom.

While mites can wreak havoc inside the hives, wasps can do so outside and Lorimer is pleased to see their numbers much lower in the Waikato now.

“There are one or two about, but this time last year you didn’t want to open your mouth around the hives, lest you get one fly in,” she says.

Explaining the reason for the year-to-year changes in hive health is no exact science, with Crowley summing it up, “sometimes when dealing with insects and nature, nature just kicks you in the arse”.


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