With the increased spread of herbicide resistance, growers need to be sure to get the most out of their programs this year. Application timing is contingent on a number of factors, and it’s important to get it right to defeat tough weeds. Below, we’ve broken down 3 misconceptions around application timing to help keep fields clean from planting through harvest.

It’s fine to spray weeds at 6”.

We learned in recent conversations at Commodity Classic that growers will apply herbicides to weeds up to 6” tall with the belief that they still provide fields with optimal control. In reality, applying a herbicide to weeds at this height would have similar effectiveness as spraying at a reduced rate. To get the best control from your post-emergence herbicide, we recommend growers spray weeds before they reach 4”.

Fields should be sprayed when all weeds are at or around the same height.

This is a common timing tool growers use to determine when it’s best to apply herbicides. Instead, it’s recommended growers pay close attention to outliers and look for the tallest weed in the field. The tallest weed should be sprayed before it reaches 4”. Waiting for all emerged weeds to reach an average height of 4” will undoubtedly allow some weeds to mature and grow to a much larger height.

Post-emergence applications aren’t needed as long as fields are clean.

Post-emergence herbicide applications help maintain the foundation of residual control from pre-emergence applications. Any breaks in treatment provide a window of opportunity for weed escapes to grow. A post-emergence application should be applied before any escapes appear.

The following video explains application timing best practices for effective weed management.

Growers timing their applications based on any of these misconceptions run the risk of herbicide resistance building in their field at an escalated rate. As a rule of thumb, growers should pay close attention to the label to help plan and time pre- and post-emergence herbicide applications.

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