Herbicide Application - Frequently Asked Questions

 
 
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 Should I wait for more weeds to emerge before spraying?
Early weed removal is recommended, especially in thin crop stands. Do not wait for more weeds to emerge. Weeds that emerge before the crop cause the most yield damage. For best control and minimum crop injury, follow the label for crop stage and weed size. Staging is critical for crop safety, especially peas. Peas can advance quickly in good growing conditions, up to 2 nodes per week and can be easily damaged by late chemical application.

What can reduce the risk of spraying in windy conditions?
Buffer zones can prevent drift damage. The size of the buffer zone is dependent on droplet size, boom height, speed, and wind strength. Spraying should be avoided when winds are over 16-20 km/hour. Dead calm should also be avoided as droplets remain suspended in the air, making them susceptible to drift.

I usually cut my water and I have good control.
This practice is not recommended for contact herbicides. Low water volumes decrease efficacy when controlling larger weeds or high weed populations. Cutting water volumes can increase the risk of crop injury, especially if surfactants are not adjusted. Low water volumes are recommended for glyphosate products in dry conditions where the dust will deactivate the product and a higher rate may be used.

The tank mix I want to use is not registered, can I still use it?
Follow label recommendations for approved tank mixes. If the combination is not listed contact the manufacturers of the products. The products may be untested, antagonistic, or cause crop injury; and a jar test will not give you that information. Contact the manufacturer for supported, off-label mixes. Recent changes with the Pest Management Regulatory Agency allow companies to support mixes where individual products are registered on a particular crop, then mixes of both products are allowed without registration


Prepared by Ag-Info Centre, Alberta Agriculture & Forestry

 
 
 
 
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For more information about the content of this document, contact the Ag-Info Centre.
This information published to the web on November 12, 2003.
Last Reviewed/Revised on December 13, 2016.