Weed Control Strategies Ahead of Harvest Combine Season

By Scout Nelson

As the harvest season approaches, it is too late to control weeds within row crops, but there is still time to stop weed seed production. Taking action now helps prevent new seeds from entering the soil seedbank. Combines are one of the biggest ways weed seeds spread, so managing weeds before harvest is vital.

Understanding weed biology is key. For example, waterhemp plants can produce up to one million seeds each. Yet over 95% of their seed bank can be degraded within four years if seed production is stopped. Giant ragweed breaks down even faster, with most of its seed bank gone in just two years. Still, even a few weed escapes can undo years of weed control progress.

Weeds like pigweed and waterhemp remain challenging because they continue producing viable seeds late in the season. Hand pulling or mowing weeds now, or spraying small grain stubble, can help stop seeds from spreading. Field edges and fence lines should also be mowed since they are often where infestations begin. If left unchecked, these weeds are easily carried by the combine into fields.

Applying 2,4-D after corn silks turn brown can be an option to reduce late-season seed production, though research shows mixed results. Keeping records of where weeds appear along field edges, waterways, and entrances is also useful for planning next year’s weed control strategies. Spot applications may reduce costs where problems are confined to small areas.

Many farmers now hand pull weeds and remove them from fields once seeds darken, indicating viability. “It is VERY tempting to just combine straight through weed patches once you’re in the combine seat, but resisting the temptation can help confine troublesome spots to smaller areas of the field.”

To limit spread, harvest clean fields first and weedy fields last. Cleaning combines between fields also helps reduce weed seed movement. These late-season practices, though time-consuming, can save effort and expense in the years to come.

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