Honey from manuka plants showed traces of insecticide residues, even though manuka largely grows far from agricultural regions.

A global study has found traces of insecticides in New Zealand honey, surprising scientists and puzzling the industry.



Swiss biology Professor Edward Mitchell led a study looking at the pervasiveness throughout the world of neonicotinoids, a class of insecticides, basing it on samples of honey sent from different regions.



Four samples of New Zealand honey, three of which were mānuka, were tested. All were found to have the insecticides.



However, the findings are at odds with testing carried out on behalf of the Ministry for Primary Industries between 2014-16, which showed no traces of neonicotinoids in honey for sale.

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Neonicotinoids are the most widely used class of insecticides worldwide. They can either be coated on a seed, providing protection from insects to all parts of the plant as it grows, or sprayed.

The study shows traces of the insecticides neonicotinoids are widespread in honey throughout the world.

Several countries are questioning their use, and France has implemented a ban on the substance.

Mitchell, who works at the University of Neuchâtel but is on sabbatical leave at Landcare Research at Lincoln University, said 75 per cent of all the samples worldwide showed traces of the insecticides. Those from the Oceania region had low concentrations and did not represent a health risk for consumers.

The puzzling aspect of the New Zealand testing was that three of the samples were mānuka, a plant which generally grows in wild scrub or forest areas, remote from where neonicotinoids are used.

Mitchell said either the mānuka was contaminated from spray drift, or else the honey was being blended with another honey, such as clover. Seeds of clover are coated with neonicotinoids before planting.

"We know mānuka isn't always pure because producers mix it with something to increase their profit, and they may have mixed it with something which had pesticides in it."

Apiculture NZ chief executive Karin Kos said she was surprised at the findings and would need to know more about the samples - where they came from and whether they were blended with other honeys that may have had some pesticide residue.

She agreed that native honeys, such as mānuka, were unlikely to be affected by pesticide use because they were gathered from the wild.

"MPI monitors pesticides, including neonics, and their published (2013-14) tests showed no detection of neonics in the honey tested. I understand that MPI has undertaken more recent monitoring since then (2015-16 yet to be published) and again there was no detection of neonics," Kos said.

New Zealand's environmental regulator, the Environmental Protection Authority (EPA) recommends no spraying near hives, budding or flowering crops; and no spraying on crops likely to be visited by bees, or when bees are foraging.

EPA chief scientist Dr Jacqueline Rowarth said the study was an example of the techniques for measurement improving.

"We're concerned and we're keeping a close watch but we have very strict regulations over the use of neonicotinoids."

"We know there are more than a million hives in New Zealand and in general even despite the disease varroa, the health of our hives is very good," Rowarth said.

Mitchell said the difference between his results and MPI's might have been related to the higher sophistication of the tests at the University of Neuchâtel.

He had asked people sending the samples to buy them directly from local producers.

"The key was to avoid blended commercial honeys that we would not be able to relate to any geographical area."

He criticised the routine coating of seeds with insecticides as "not a smart thing. It's like taking broad spectrum antibiotics just in case something attacks you, no doctor would support that".

"If it's coated on the seed the whole plant is toxic, the soil is toxic, 95 per cent can remain in the soil from one year to the next. It accumulates and can go into groundwater and aquifers.

"There's the risk of contamination of the environment, there's also the risk of developing resistance in pests and meanwhile the load of pesticide is increasing globally," Mitchell said.