Former Apiculture New Zealand board member Ricki Leahy said recent reports of moth-like, passion vine hopper insects smothering Greymouth plants was something southern beekeepers needed to take seriously and "actually get some samples of their honey tested".
The introduced passion vine hoppers fed 0on sap from native tutu (Coriaria arborea) plants and secreted honeydew containing the plant toxin tutin, which bees could collect and transfer to honey.
The main risk period was from January to April, and typically was only of concern for honey in the North Island and the top of the South Island.
Honey produced below a latitude of 42 degr0ees south, below about Westport on the West Coast and Cape Campbell on the east coast of the South Island, was considered "low risk", because the insects could not survive southern frosts.
This, however, had been "quite an exceptional summer" on the West Coast.
Nevertheless, Mr Leahy, of Murchison, said he had been beekeeping for about 50 years "and in all that time, we’ve never found tutin in our honey".
"Just because there’s lots of the vine hoppers flying around it mightn’t mean that there are any further problems, but it is very interesting," he said.
"I’ve thought with climate change there could be a migration of all those types of insects.
"Times are changing, we have to be aware of it."
The Medical Journal of New Zealand has detailed an incident in 2008 when a rural hospital in Waikato had three people from a six-person family arrive at their emergency department with sudden onset of vomiting and headache after eating tutin-tainted honeycomb.
Then, it was not until the late 1880s, that vomiting, headache and delirium was reported after eating honey made in New Zealand.
That happened after the accidental introduction of passion vine hoppers (Scolypopa australis) from Australia around 1870.
Outbreaks of toxic honey had then happened occasionally in warmer parts of New Zealand over the last 130 years, the report said.
Catlins Honey director Grant Hayes, of Branxholme, Southland, said beekeepers of all stripes throughout the country should be aware of the risk posed by tutin, regardless of whether their operation was based below 42 degrees south.
Though he had seen no sign of passion vine hoppers in his patch, the tutu plant was "everywhere".
"Old timers" in the Catlins knew it because cattle died from eating it, Mr Hayes said.
"It’s something any proactive beekeeper should be looking out for, full-stop."
A Ministry for Primary Industries spokeswoman said New Zealand beekeepers were required to adhere to a "tutin-in-honey food standard" that set out maximum allowable levels of the toxin and required beekeepers to keep a record to show their honey complied with the standard.
"If beekeepers in these low-risk areas are seeing an increase in passion vine hoppers, they need to ensure that tutin levels in their honey do not pose a health risk to consumers.
"If there is evidence of a heightened risk, we will work with beekeepers to manage it."
