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The weed killer that killed our crop

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Our family business includes growing bedding plants. In the spring of 2010 every tomato, pepper and marigold we started curled up grotesquely and died. After weeks of trying new fixes and consulting with a plant pathologist, we discovered that the culprit was in our compost.

It looked like herbicide damage, so we asked the municipality what they had been spraying. Bingo. Tordon 101.

A decade of being certified organic taught us to be careful about what we use in our growing mediums. But in 2008 we missed asking our rural municipality, the R.M. of Morton, to not spray the ditches where we made hay to feed our horses and later used the composted manure in our growing medium.

We researched Tordon, also known as picloram, and learned Health Canada (through the Pest Management Regulatory Agency, or PMRA) forbids picloram to be sprayed in ditches. It is highly mobile in water and a variety of sources clearly show this herbicide damages ecosystems and human health.

Health Canada is not alone in its cautions. In the 1990s, both the Environmental Effects Branch and the Environmental Fate and Ground Water Branch of the U.S. Environmental Protection Agency (EPA) recommended that the use of picloram be discontinued. This was later rejected by an EPA governing body. California withdrew picloram registrations because the manufacturer did not provide data about health and groundwater contamination required in that state. When Sweden determined picloram to be unacceptably persistent and mobile, it was banned.

Picloram survives digestion by large mammals and rigorous composting and will kill tomato seedlings at the extremely low level of three parts per billion (ppb). Our compost tested at 76 ppb. Small fish die at one ppb levels and it disrupts reproductive functions of small mammals. Picloram persists in soil for up to five years, unless rain or snow-melt transports it into wetlands, river/lake systems and aquifers. In 2005, Chauvin, Alta., found picloram in the community's well water. It was killing their gardens.

We asked a chemical manufacturer representative what we should do with the contaminated compost already dug into our garden. She said, "Wait for the rain to wash it away." Wash it away to where? Into our aquifer or the Pembina River?

PMRA labelling for picloram products requires that users be notified to NOT apply it directly to freshwater habitats (such as lakes, rivers, sloughs, ponds, prairie potholes, creeks, marshes, streams, reservoirs, ditches and wetlands), estuaries or marine habitats, to not contaminate irrigation or drinking water supplies or aquatic habitats by cleaning of equipment or disposal of wastes.

Labels must include an environmental hazard section identifying picloram as persistent, that picloram products not be applied two years in a row, that a single use may result in contamination of groundwater particularly in areas where soils are permeable (e.g. sandy soil), the depth to the water table is shallow, slopes are steep, soil is clay or compacted, which increases runoff. Application when heavy rain is forecast is to be avoided. Finally, all of these directions must be followed by law.

We requested Manitoba Conservation's Pesticide Section Licensing Branch not authorize Tordon for use in our ditches. They told us that in January 2009, the PMRA publicized a re-evaluation for picloram and concluded that the available scientific information found that products containing picloram do not present unacceptable risks to human health or the environment when used according to label directions. But we were not informed as to the restrictive nature of these instructions or where to find them in writing.

Our municipal councillors maintain they were mystified about the province's insistence in using picloram to control leafy spurge and milkweed when Health Canada says it was not to be sprayed in ditches.

We called the Manitoba weed supervisors president who told us that to weed districts, "ditch'" means "irrigation ditch." We asked PMRA for an official definition and they told us that they defined "ditch" as a "sunken or low area beside roads or facilities used for purpose of drainage. It can be either artificial or natural."

CBC Manitoba also sought PMRA clarification about the legality of spraying Tordon in ditches and was told it was fine to spray picloram in dry ditches when there is no forecast of rain. However, the PMRA re-evaluation document specifically states picloram cannot be sprayed in freshwater habitats including ditches, because they are designed to hold and/or move water and are always potential freshwater habitat.

We want to trust government to protect public and environmental health. While picloram concerns regulators, there are no municipal and very little provincial or federal resources to test our water and soils for levels of picloram and other pesticides of concern. Accurate mapping and licence conditions to guide weed supervisors in applying chemicals is lacking.

Alternative soil management, animal control or integrated pest management practices are rarely being explored and implemented. Instead, in 2010, the provincially funded weed supervisors conference invited a pesticide industry speaker to warn supervisors that the pesticide ban in Ontario was seriously hurting that province's economy. Blame was assigned to misguided environmentalists.

What to do? The sharing of balanced information with the public and municipal councillors is needed. Municipalities are legally required to notify the public what chemicals they plan to use each year and notice of how any one of them or any combination may cause ill health or damage to environmental diversity is not required. Conservation should suspend the use of picloram in public places until the legality of its use is clarified, its safety verified, testing/mapping capacity is put in place and information from a variety of sources is made available so that citizens can respond knowledgeably. Weed supervisors and researchers need to work together to explore diversity-enhancing weed control methods. Finally, the province needs to respond quickly to public concerns about pesticide use.

David M. Neufeld and Magdalene Andres live in the Manitoba R.M. of Morton.

Republished from the Winnipeg Free Press print edition November 14, 2012 A10

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