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Weed Control Guide Updates (05/12/16)

We have received many inquiries about a change in the 2016 ND Weed Control Guide on page 6 showing a 0 day plant back restriction to wheat following a 2,4-D application.

Weed Control Guide Updates

We have received many inquiries about a change in the 2016 ND Weed Control Guide on page 6 showing a 0 day plant back restriction to wheat following a 2,4-D application.

Many years ago Dr. John Nalewaja (NDSU Weed Scientist) tested 2,4-D applied PRE on wheat and found wheat to have excellent tolerance. We listed 2,4-D PRE in early weed guides based on the wording on page 5 in the weed guide under ‘LEGAL DISCLAIMER’ that, “The weed control suggestion presented in this guide are based…..on information obtained from the North Dakota Agricultural Experiment Station, and reports in the North Dakota Weed Control Research.” John reported this research in ND Weed Control Research publications.

In 2009, NDSU weed scientists changed the rotation in the weed guide to reflect the 30 days rotation restriction following 2,4-D as shown on product labels.

Earlier this spring Dr. Kirk Howatt reviewed this restriction on several labels from different registrants. He found the label wording had changed at some undetermined point.

The following is the wording found on most 2,4-D labels:

Labeled Crops:

Within 29 days after an application of this product, plant only those crops listed on this or other registered 2,4-D labels. Follow more specific limitations, if any, provided in directions for specific crops. Labeled crops may be at risk of crop injury or loss if planted soon after application, especially during the first 14 days. Degradation factors described below should be considered in weighing this risk.

Other Crops:

All other crops may be planted 30 or more days after application without concern for illegal residues in the planted crop. However, under certain conditions, there may be a risk of injury to susceptible crops. Degradation factors described below should be considered in weighing this risk. Under normal conditions, any crop may be planted without risk of injury if at least 90 days of soil temperatures above freezing have elapsed since application.

Below Dr. Howatt paraphrases as he understand the labels:

  1. Crops labeled for in-season 2,4-D application can be seeded within 29 days of treatment.
  2. Crops not labeled for treatment with 2,4-D in-season cannot be seeded until 30 days after 2,4-D application. 
  3. None of the labels included a minimum waiting period for crops on the label.
  4. All labels reviewed used essentially the same wording.

One last point: Soil degradation of 2,4-D ester is significantly more rapid than 2,4-D amine, as indicated on page 67 on the weed guide. Use a 2,4-D ester to decrease the risk of any crop response following a PRE 2,4-D application,.

Rich Zollinger

Extension Weed Specialist

 

Kirk Howatt

NDSU Weed Scientist

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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