Preharvest Herbicide a Management Tool to Aid Cereal Crop Harvest

From the Aug 31, 2009 Issue of Agri-News

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"One approach that producers could utilize is the application of a glyphosate product to a standing cereal crop," says Mark Cutts, crop specialist with Alberta Agriculture and Rural Development. "Applying glyphosate to a standing crop is commonly referred to as preharvest and is primarily used as a management tool to control perennial weeds such as quackgrass and Canada thistle.

"Glyphosate is a systemic herbicide that moves through the foliage into the root system and results in death of the entire plant. As a result of its behaviour in the plant, glyphosate applied to a standing cereal crop will terminate the growth of the crop and, over a period of time the entire field will dry down or ripen. The advantage of this approach is the elimination of the variable crop stages and improved harvest management. However, it should be recognized that the growth of the less mature portions of the field will be terminated and as a result will not contribute to yield."

For producers considering preharvest herbicide as a management tool for their cereal crops there are several factors that need to be considered:

Registered cereal crops: preharvest herbicide is registered on wheat, barley and oats. Producers growing barley for malt should contact their malt buyer to ensure a preharvest application is acceptable. It should also be noted that a preharvest application should not be applied to a cereal crop that is being grown for seed due to potential reductions in germination and vigour levels.
Timing of application: for cereal crops, preharvest herbicide applications should occur when grain moisture is less than 30 per cent. This correlates to the hard dough stage of the grain. At this stage, a thumb nail impression remains on the seed. When planning a preharvest application in a field with two or more crop stages, producers will need to base the timing of the preharvest application on the most mature regions of the field.
Rate of application: the standard rate for glyphosate in a preharvest herbicide application is 360 grams active ingredient per acre. Due to variations in the concentration of glyphosate products, producers will need to ensure that the glyphosate product is being applied at the proper rate. For example, the application rate will vary from 0.67 to 1.00 litres per acre depending upon the product being used.
Time required for crop dry down: in general, a crop will require 10 to 14 days to dry down to become a uniform stand. The number of days required to achieve dry down will vary with environmental conditions. For example a fall with cool, wet conditions will extend the time required to achieve dry down.

The environmental conditions in 2009 have resulted in many cereal fields having two or more growth stages present. Proper management of these fields is required in order to ensure an efficient harvest of these crops. For more information on harvest management of these crops, contact the Ag-Info Centre at 310-FARM.

Contact:
Mark Cutts
310-FARM (3276)


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