From Tierney's Real News:
ShareIn simple terms, spraying glyphosate at the end of the season works like a chemical “off switch” to kill the crop and help it dry down more quickly so it can be harvested on schedule. This practice is called pre‑harvest application. It is used on some wheat acres, especially in cooler or wetter northern climates, but it is not universal on all U.S. wheat.
Why do farmers do this?
In cold or wet years, wheat can stay green and “wet” too long. Killing the plant helps it dry faster so the farmer can harvest before rain, frost, or snow.
Sometimes part of a field is ripe while another part is still green. Spraying helps the entire field reach a similar dryness so the combine doesn’t plug with green stems.
Late‑season green weeds can tangle in machinery and slow everything down. A pre‑harvest spray helps “burn down” those weeds and smooths out harvest.
Farmers wait until the wheat is mature – meaning the grain is fully formed and the moisture in the kernels has dropped to around 30% or less. A common “thumbnail test” is pressing a fingernail into a kernel; if the dent stays, the grain is mature enough for a pre‑harvest treatment.
At that point, a sprayer applies either true desiccants like diquat or systemic herbicides like glyphosate over the field. Contact desiccants kill green growth very quickly and dry the crop in a few days; glyphosate works more slowly and is technically labeled for weed control, but in practice it also helps the crop finish drying and ripening in bad conditions.
Once the plants are brown and brittle and grain moisture is down near storage levels (around 14%), the combine goes in and harvests.
Glyphosate has been around since the mid‑1970s, but its use as a late‑season tool became more common in the late 1980s and 1990s and expanded in the 2000s in places like Canada, the northern U.S., and the U.K., where early cold and wet weather can shut down the season fast. (Read more.)


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