The Green Party is calling for an urgent Environment Protection Authority (EPA) review of the pesticides known as neonicotinoids, in the light of new research showing they can harm bees even at low doses and reduce pollination.
Photo: 123RF
The chemicals are used widely in the horticultural industry as systemic insecticides.
But Green MP Steffan Browning said the latest research showed they damaged bees' ability to forage, and caused changes in their breeding patterns.
A study by independent British scientists, published in Nature, found bumblebees exposed to neonicotinoids in their environment visited fewer trees and collected pollen less often.
As a result, pollination levels fell by 30 percent and the apples that were produced had fewer seeds.
Mr Browning, who was a commercial organic grower before he entered Parliament, said the study had serious implications for all growers.
"The percentage drop was actually on the amount of pollination that was going on, so they were measuring it in apples and showing that there was a drop in the number of seeds, which is obviously as a result of pollination.
"With some crops, a drop in seeds means a drop in size of fruit," he said.
"This is the first time apparently that they've shown that direct link in terms of the amount of pollination reduction because of the exposure to neonicotinoid pesticides."
Mr Browning said the second study that should indicate a rethink of neonicotinoids was one by French scientists.
It has been accepted that the 'neonics' at acute levels kill bees - but the debate has been whether that translates to population declines in the wild, where the bees are exposed to sub-lethal doses from plant pollen and nectar.
The French study showed honeybees foraging around treated crops died off at a faster rate than normal - and colonies tried to compensate by producing more workers, Mr Browning said.
"They started to change their development of their brood and they focused on developing more worker bees to compensate for the foragers that were dying, and less on the drones for the next year's queen reproduction, effectively.
"So they were making sure they were keeping their worker numbers up to keep the pollen and nectar coming into the hive, and then they would focus at a later stage on the drones."
A reduction in drone numbers might seem like a clever adaptation but would ultimately lead to a smaller gene pool and a less resilient bee population, he said.
The EPA, which approves pesticides for use in New Zealand, should take note of the two independent studies - and urgently reassess its approval of neonicotinoids, he said.
The EPA said it was aware of the two new studies into neonicotinoids.
Under the Hazardous Substances and New Organisms Act, the EPA regulates on the basis of risk and existing approvals have stringent controls to manage them, the agency said.
The two studies did not identify any gaps in those controls and it would only review existing approvals if new studies indicated its risk management measures were inadequate, it said.
