David Neufeld learned the hard way how persistent this herbicide is and now wonders how surface and groundwater are affected
A Boissevain farmer is questioning the safety of a herbicide commonly sprayed on ditch weeds after discovering it makes the compost he uses in his organic greenhouse toxic to bedding plants.
David Neufeld got a nasty surprise when his greenhouse tomatoes suddenly died in 2010. A Winnipeg laboratory found the composted horse manure he was using to feed the plants contained 75 parts per billion of picloram, a herbicide that is combined with 2,4-D in the product Tordon 101.
“It didn’t sound like a lot to us until we found out that three parts per billion can kill tomato seedlings,” Neufeld wrote in an email. “No wonder we had a problem in the greenhouse. We began to ask ourselves, if picloram is so deadly at such low concentrations, what will it take to clear our land of its effect?”
It turns out the Rural Municipality of Morton had used the product to control leafy spurge and milkweed on the roadside ditches where Neufeld cuts hay for his horses.
Despite going through the horses’ digestive system, followed by composting, the compost contained high enough concentrations to kill the bedding plants Neufeld markets to area gardeners.
Tordon 101 is registered by the Pesticide Management Regulatory Agency (PMRA) for use in Canada. While Tordon 101 is not to be sprayed in waterways, a Health Canada official said in an Oct. 31 email spraying in dry ditches is permitted.
So long as Tordon 101 is approved by federal and provincial authorities the Rural Municipality of Morton will continue to use it, Councillor Lonnie Graham said in an interview. The province’s Noxious Weeds Act compels municipalities to control noxious weeds.
Neufeld said he should have checked with the municipality to find out if the ditches had been sprayed. (Municipalities are required to advertise their herbicide programs so the public is aware of them.)
The Tordon 101 label and the province’s Guide to Field Crop Protection warn against using plants sprayed with picloram in compost or the manure resulting from the consumption of treated plants because picloram residue can harm susceptible crops.
Neufeld removed the poisonous compost from his greenhouse, but what about his garden? An official from Dow AgroSciences told him rain would flush it out. That caused Neufeld to worry about the impact picloram could have on surface and groundwater and ultimately people’s health.
“I have so many layers of concern when it doesn’t seem that we as a society know what we’re doing,” he said in an interview.
PMRA’s website states picloram poses a risk to fish. And according to Neufeld, California has banned picloram because of the risk it poses to groundwater. The herbicide is also forbidden in Sweden, he said.
The Tordon 101 label states groundwater pollution is a risk with picloram on sandy soils. The label adds precautions should be taken to avoid run-off. Picloram also is recognized for persisting in the soil. That’s how it provides residual weed control.
“I don’t know how Health Canada can start saying that it’s OK in dry ditches when the day after it’s applied we can have a huge thunderstorm,” he said. “All our ditches here go straight down into the Pembina River, which goes into the Red, which goes into Lake Winnipeg.”
Many of the soils in the RM of Morton are sandy, according to Neufeld.
“Do applicators stop spraying in low areas where there might be water sitting?” he asked. “Is anybody doing any testing of river water and groundwater for picloram? And if they are not doing any testing how can we be sure that it’s OK to spray the stuff even in dry ditches when we know that it stays in the soil up to five years.”
Municipalities should provide more information about the herbicides they’re spraying and the risks in their advertisements alerting the public to their spray plans, Neufeld said.
Health Canada re-evaluated picloram in 2009 and implemented new restrictions to reduce the product’s risk, a Health Canada official said in an email.
“These include advisory label statements to reduce potential surface and groundwater contamination, a reduction in the application rates, and specific buffer zones to protect non-target sensitive aquatic organisms and terrestrial plants,” the official wrote.
The weed supervisor and the Rural Municipality of Morton followed standard procedures with Pesticide Use Permits and The Noxious Weed Act when applying Tordon to ditches in the municipality, a provincial official said in an email.