Common Preharvest Questions in Flax

mca2022dev on September 9, 2022

What is the staging for a preharvest or desiccation in flax?

Flax is considered physiologically mature when 75% of the bolls (in the field or on a plant) are brown and the boll segments have begun to separate. This is a visual rating that corresponds to a grain moisture content of around 30% and is known as the 75% boll turn or 75% brown boll stage.

Figure 1: Flax Maturity Ratings. Credit: SaskFlax

What is the difference between a preharvest aid and a desiccant?

Two types of chemicals are available to assist with flax harvest management: pre-harvest herbicides (sometimes called harvest-aids) and desiccants.

Pre-harvest herbicides are non-selective systemic herbicides that provide late season perennial weed control and may improve the harvestability of the crop by reducing the amount of green material in the field.
Desiccants are non-selective herbicides that rapidly dry down the crop and weeds to allow for an earlier harvest.

Figure 2: Comparison between preharvest herbicide and desiccant characteristics. Credit: SaskFlax

Can we use glyphosate as a preharvest aid?

Since it does terminate the crop, preharvest glyphosate may assist with stem dry-down and harvestability, however it is expected that the effects of glyphosate applied alone on flax dry-down can be slow and potentially inconsistent depending on environmental conditions. This all being said, at this time, it is not a recommendation of Manitoba Crop Alliance to apply glyphosate as a preharvest aid due to inconsistent results with maximum residue limit (MRL) testing. If a producer must use glyphosate, it is strongly recommended to speak with their grain buyer to determine if a glyphosate application to their flax will be a marketing concern.

What are the current registered preharvest aids and desiccants for flax in Manitoba?