Mr Yanke had yet to receive the test results. Police had been notified, but could not act until lab tests confirmed that poison was involved.
He had about 1000 'nukes,' hives specifically for breeding queens, in the valley, about 300 of which had been wiped out or badly affected.
The poisoning, if proven, was symptomatic of the "craziness sweeping the industry," with large numbers of people taking up beekeeping with no experience or real interest in bees, but driven by greed and overstated reports of the prices paid for manuka honey, he said.
Large companies were moving in, squeezing out small-scale beekeepers, and some areas had so many hives there was not enough food for the bees.
"All this could kill the golden goose,' he added.
The upside of the suspected poisoning was the almost overwhelming support he had been shown by fellow beekeepers.
"They all say it's a terrible thing to do, and a real beekeeper wouldn't do it." And his business would bounce back.
A ministry spokesman said apiarists often made contact when they experienced unexplained deaths or declines in their hives. As part of its biosecurity role MPI tested for exotic pests and diseases. If that was ruled out, and toxicity was a possible cause, the incident was referred to the Environmental Protection Authority.
MPI knew of three cases of hive poisoning in New Zealand last year. One in Christchurch in December was deemed accidental, but another case, causing "significant deaths" in Northland hives in April, was thought to have been deliberate.
"Manuka fever" and competition for hive sites is thought to have been behind an arson on beehives at Ohaeawai in September. A note was left next to the burning hives, but police would not reveal its contents.
A large number of hives, thought to belong to a large honey company, was dumped on West Coast Road in the North Hokianga last year, while beehive thefts have become such a problem that Kawakawa police devised a plan last year aimed at catching offenders as they transport stolen hives by night.