Hundreds of thousands of bees have dropped dead in the last week near Nelson.
No one is sure who is to blame for the crisis at hives near the Mangles Valley in Murchison.
Veteran beekeeper Ricki Leahy says millions of his insects dropped dead in a matter of days.
"It's pretty bad, it's completely disrupted our autumn queen rearing. There's lots of dead hives, hives which are still dying, and hives which are very weak," he told Newshub.
Mr Leahy first noticed dead bees on Friday. Since then, nearly 200 hives have been devastated.
Mr Leahy believes that wasp poison is behind the deaths but he's not sure where it came from or who is behind it.
"I just really think someone's made a huge blue and I'm just hoping there's nothing sinister," he said.
Wasp populations are booming in the area and baits are required to be meat-based to avoid attracting honey bees.
Another nearby beekeeper has lost up to 80 hives, Mr Leahy says. He hopes a few of the hives in his apiary will survive to lessen the blow to his company, which produces Tutaki honey.
The apiculture community is rallying around the beekeepers, but there's not much they can do.
Apiculture New Zealand CEO Karin Kos said: "It's just devastating for Ricki and the other beekeepers involved in this. Ricki is a beekeeper with huge experience - he's a valued member of the Apiculture New Zealand board with many years of experience."
The Ministry for Primary Industries says it's investigating and there are no reports of mass bee deaths happening anywhere else.
Bee samples are now being sent for testing and an apicultural expert is working with the beekeepers.