Beekeepers are concerned about reports of varroa mite showing resistance to chemical treatments in some hives around Auckland and the Waikato.
Varroa is the biggest killer of bees world-wide.
The Beekeepers Association says the anecdotal evidence is the first real sign of what has been expected since the year 2000 when varroa was first detected in New Zealand.
Dennis Crowley, from the Tauranga branch of the association, says beekeepers that have been using a chemical treatment for varroa may start to see hives tipping over this winter.
He says this latest news may see another wave of apiarists leaving the industry.
Katikati beekeeper Greg Wagstaff says he uses chemical treatments to keep varroa mite under control.
Rotorua beekeeper Russell Berry, who supplies hives to the Bay of Plenty, says he used four chemical treatments.
Federated Farmers is advising farmers to be aware of how their activity affects on bee colonies and care needs to be taken.