Hantz Honey operations head Barry Hantz lost about 10% of his hives to the parasites last winter and is spending $150,000 a year on strip treatment.
He is not alone. A national survey by the beekeeping industry and Ministry for Primary Industries found that nearly 14% of the country's bee hives were lost over the same period. Nearly 40% of them were taken out by varroa infestations.
For the first time, beekeepers in the New Zealand Colony Loss Survey report it is the most common reason for hive losses over the winter.
Mr Hantz said varroa losses had increased and were higher than the Leeston family operation wanted.
It cost them $200 to $300 to replace each of the 400 to 500 hives they lost over winter.
They increased varroa treatment from twice a year to triple-treating for about 25% of their hives last winter because of large losses in early autumn, he said.
"Since 2015 the losses have got higher, hence we have gone into this monitoring and triple treating. We need to change something because that number will only grow if we do the same thing ... When we get to that 10% we notice it’s having an effect on our bottom line."
Hantz Honey sells about 1500 queen bees a year and demand is increasing with varroa deaths as once a queen dies, the colony is lost.
The survey found 5.3% of all living colonies were lost to varroa and related complications over the winter, which is much higher than 1.6% five years ago.
Some areas are harder-hit than others. Mid-North Island — including Waikato, Bay of Plenty, Gisborne and Hawke’s Bay — reported 18.7% winter losses, 8.6% of all colonies being lost to varroa.
Some of the region’s larger operations of 15,000 to 20,000 hives are reported to be losing 6000-7000 hives to the disease,
In contrast, central South Island beekeepers had the second lowest overall loss of 10%, and 2.8% attributed to varroa.
Apiculture New Zealand is worried that about 4% of all surveyed beekeepers did not treat for varroa during the 2020-21 season and about a quarter of them did not monitor the success of their treatments.
Mr Hantz said they never used to monitor treatment, but did now to keep tabs on the mites and detect problem areas.
Monitoring allowed them to trace a "random" result in a yard to treatment strips being missed by the team and this was followed up with another treatment to stop mites spreading,he said.
Many beekeepers have come through a honey season just below average in Canterbury.
Mr Hantz said hopes were high for a good crop after early rain in December, but temperatures were not warm enough.
Their 105 tonnes of honey including manuka honey and another one or two tonnes of honeycomb was down on last year. Manuka production had been "quite good" and pollination work had assisted with bringing in revenue, he said.
