Pre-Harvest Use of Glyphosate on Cereal Crops
By Scott Banks
- OMAF Kemptville
Several glyphosate products are registered for pre-harvest application in barley, oats and wheat. Glyphosate products are not registered for any crops if grown for seed production because glyphosate applied under the wrong conditions may reduce seed germination. Malting barley standards require at least 95% germination. Therefore, unless it is really necessary, avoid applying glyphosate on barley intended for malting to reduce the risk of not making malting barley grade.
In other situations, the advantage of using these products is that it can give you another option to control some of the more difficult weeds, particularly perennial weeds such as quack/twitchgrass, Canada thistle, sow thistle and dandelions. The effectiveness on some weeds like sow thistle and milkweed will depend on stage of the weed. In addition to helping with weed control for next year, you could improve harvest conditions in fields with a lot of weed pressure. The product should be applied when the crop is 30% grain moisture or less. In cereals, this is at the hard dough stage, when you can only leave a thumbnail impression on the seed. Apply only during the period of 7 to 14 days before harvest to ensure the best weed control and to maximize harvest management benefits. Earlier applications may reduce crop yield and /or quality and may lead to excess glyphosate residues in the crop.
Strawberry growers use a lot of cereal straw for winter mulch. This straw should be free from weeds and weed seeds. Note that cereal crop growers can use a pre-harvest treatment of glyphosate of 7 to 14 days prior to harvest. While this application may also help control weeds, there may be potential glyphosate activity on strawberry plants if this straw is used for mulch. Strawberry growers should not use straw for mulch if pre-harvest glyphosate was applied.