TORONTO — Systemic insecticides threaten far more than honey-bees, according a symposium here at York University on April 19.
Speakers at the event linked neonicotinoids and other systemic chemicals to risks for earthworms and other soil invertebrates, butterflies, wild pollinators and people.
David Kreutzweiser, with Natural Resources Canada, said he evaluated peer-reviewed scientific papers in sounding the warning for soil invertebrates.
“As it turns out, overall harmful effects are likely for earthworms at concentrations of neonicotinoids likely to be found in fields,” Kreutzweiser said.
“There should be an increasing emphasis on alternative control products and things like integrated pest management.”
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Kreutzweiser said earthworms are viewed as a kind of canary in the coal mine for soil-dwelling invertebrates. With a couple exceptions, such ground beetles, there’s been little research on other species.
Earthworms can be impacted when they consume soil or plant matter containing the insecticides or through dermal contact, which may increase the toxicity of chemicals by up to ten times, he said.
While earthworms face the risk of being killed outright, neonicotin-oids also have sub-lethal impacts. With low level exposures, as little as 0.1 to 0.5 parts per million, they’re less likely to feed, he said.
That’s an important consideration since earthworms and other soil invertebrates have important soil functions, including the role they play in recycling nutrients.
Kreutzweiser cautioned that while there is a growing body of evidence showing impacts on soil invertebrates, uncertainty remains.
Most studies have been conducted under laboratory conditions. With the lack of field study data, the extent of the danger could either be less or greater than what’s currently estimated.
Another complication revolves around the persistence of neon-icotinoids in the soil, especially when there is high organic matter or when soils tend to be wet.
Kreutzweiser said that in instances when neonicotinoids are used on the same field repeatedly, levels in the soil may accumulate.
“It can persist in soils for months or years where this is used on a regular basis.”
Amro Zayed, who heads a genetic research program at York University’s Department of Biology, said he’s uncovered an interaction between neonicotinoid insecticides and a fungicide.
“In cases when you have boscalid application plus neonicotinoids present you could have lethal impacts,” Amro Zayed said.
“We think it may make neon-icotinoids two times as toxic to honeybees.”
Zayed said there are plans for the research, led by graduate student Nadia Tsvetko, to be published. It involved the location of two sets of honeybee colonies in southern Ontario, one set placed within with 500 metres of corn field locations and the other set at least three kilometres from the closest corn field.
Zayed said research also revealed that the bees were exposed to the insecticides for lengthy periods, for up to three to four months and neonicotinoids were found in locations distant from corn production.
The findings lend credence to the idea that dust is not the only concern, he said. In addition, the amounts of neonicotinoids found during the research are similar to those used for “field-realistic” studies that have demonstrated sub-lethal honeybee impacts.
Larvae, nurse bees, foraging bees, fresh nectar, fresh pollen and dead bees were analyzed.
Of the neonicotinoids found, 61 percent was in the pollen, 15 percent in dead bees,10 percent in nectar and lesser amounts in the other sample types.
“Most of the pollen didn’t come from the crops. Most of it came from the normal plants bees are attracted to,” Zayed said.
