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Potent, popular herbicide now available in Canada

The second-largest selling herbicide in the world is now available in Canada.

Gramoxone PDQ is a non-selective herbicide designed to burn off annual weeds and the tops of most perennials.

The Zeneca product has been registered for use this spring for western farmers. The company is focusing the product on producers with minimum and zero tillage operations or those concerned about glyphosate resistance.

“This should compete well with glyphosate products,”said Dave Kelner, weed specialist for Manitoba Agriculture, in Carman, Man.

Gramoxone PDQ is a 2:1 mix of paraquat and diquat. Diquat is better known in Canada as Reglone. The herbicide is expected to be applied before seeding or before crop emergence, to control tough annuals such as kochia and buckwheat and to kill volunteer glyphosate resistant canola. Often producers need to add 2,4-D to glyphosate products to deal with these hard to kill plants. The 2,4-D residues can remain active in the soil for up to four weeks and hurt young broadleaf and oilseed crops.

“Cool weather hurts glyphosate performance while the paraquat diquat will still give powerful non-selective control,” said Trevor Heck of Zeneca Agro in Calgary.

Doug McKell, of the Saskatchewan Soil Conservation Association in Indian Head, Sask., said the product becomes “another tool in the weed control tool box. It will be good for those worried about glyphosate resistance in weed populations.”

The product causes cell death through ion leakage in plant cell membranes. It is fast-acting and does not require plant uptake of the herbicide, but the plant should be actively growing. The manufacturer suggests symptoms may appear as soon as 30 minutes after application with most weeds controlled within 48 hours. Seeding can take place the same day and the product is rainfast in 15 minutes.

Farmers should be aware the product is more toxic than other non-specific herbicides.

“It (paraquat) is known to be toxic to all forms of life ranging from bacteria through human,” says a study published at the University of Waterloo, in Ontario, last year.

Heck suggests greater care should be taken with the product than with some other herbicides.

“General toxicity is higher than for most other farm chemicals. We are comfortable with the product as long as producers follow the recommendations and use the appropriate safety equipment,” said Heck.

Other studies suggest paraquat may hurt nitrogen fixing rhizobia in the soil. Producers concerned about this should contact Zeneca Agro directly.

McKell said this shouldn’t be a problem as the bacteria populations will be able to rebuild quickly.

The product bonds quickly to clay and is rendered unavailable for further herbicide action soon after contact with the soil particles. Because of this, clean, filtered water is needed for application.

The manufacturer suggests a minimum rate of 0.81 litre of product to 40 litres of water per acre for use in spring applications. At this rate, the product will cost about $8 per acre, but an exact price has not been established.

A 30-day waiting period for grazing must be observed and the product cannot be applied by air.

For more information contact Zeneca Agro at 1-800-665-9250.

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