Thursday, July 7, 2022

Pesticide use blamed for bee hive losses

Recent reported heavy losses of bee hives have been blamed on the widespread use of neonicotinoids in agriculture and horticulture, but there is little local evidence that this is the cause.

So-called “systemic” products like imidacloprid, which has chemical structures related to nicotine, are the major new class of insecticides introduced worldwide over the past 50 years.

They are used as seed coatings in agriculture, as foliar sprays in horticulture and even as a topical application for flea control in household pets.

One of the main advantages of neonicotinoids is insect toxicity without harming mammals.

Imidacloprid (with brand names like Gaucho, Confidor and Advantage) is more toxic to bees than organophosphates or pyrethrums and it has been suggested that even sub-lethal doses can cause colony collapse disorder (CCD).

New Zealand does not have officially recognised CCD but neither are researchers testing agricultural insecticides on bee populations.

Federated Farmers bee section chairman John Hartnell, of Christchurch, said ways must be found to carry out relevant research, but a majority of bee keepers were reluctant to levy themselves.

Former Green MP Sue Kedgley wrote an opinion piece recently for The New Zealand Herald repeating anecdotal evidence of large-scale hive losses and calling on the government to monitor bee health and try to prevent the huge population collapses being seen overseas.

“Pesticides have become the prime suspect in colony collapse disorder that is decimating bee numbers in many parts of the world,” she wrote.

“I hope that the government would respond with some urgency to scientific findings that a new generation of pesticides that are widely used in NZ are poisonous to bees, even at extremely low doses that had been assumed to be safe.”

Kedgley said the seed coatings were designed to break down as the seedling grew and disperse throughout the plant, even as far as pollen and nectar.

Hartnell provided an example of maize grown from coated seed and subsequently suffering some plant breakage, then exuding moisture that could contain traces of neonicotinoids, which bees might drink.

“While we have many of the diseases and pests which are factors in CCD we are fortunate not to have European Foulbrood or Israeli Paralysis Virus, which I believe are key factors if CCD were to enter our industry,” he said.

“These pests or diseases weaken the bees’ resistance and this opens a pathway for pesticides and chemical contamination to impact further on bee health.

“For example, Varroa mite pierces the bee body and this open wound allows diseases and viruses which may have been in the bee population for years a soft entry point, and the same could be said of chemicals.

“Other issues such as lack of food stores, missed or late Varroa treatments, poor cold winter hive sites lacking pollen sources, and wet spring conditions all play a part in bee deaths.”

Hartnell said the two national bee organisations – Federated Farmers and the National Beekeepers Association – had less than 25% of total registered keepers in their memberships.

“Industry funds are pitiful to say the least, but a response to Federated Farmers’ proposal last year for a modest voluntary levy was very disappointing.”

Hartnell said lack of industry funding was critical when proposing research and monitoring activities on a joint basis with either government or agricultural chemical manufacturers.

He also drew attention to a recent European Commission report, which said the use of neonicotinoids was increasingly held responsible for honeybee losses.

“Sub-lethal doses can also result in a wide range of behavioural disturbances, as well as a reduction in breeding success and disease resistance.”

The European Food Safety Authority has been charged with a review of the approved uses of neonicotinoid insecticides.

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