Herbicide tolerant crops can tolerate herbicides at application rates that would kill non-herbicide tolerant hybrids or varieties of the same crop species. Crops with traits for herbicide tolerance allow farmers to apply herbicides to their crops that they would otherwise be unable to utilize without causing death or unacceptableinjury to that crop.
Properly managing herbicide tolerant crop technology is important to preserving the effectiveness and value of the tolerant crop seed and its corresponding herbicides in the future. Growers utilizing herbicide programs that include herbicide tolerant crops can do so on an annual basis, provided the technology is managed effectively. If you have any questions after reviewing this information, please contact your Pioneer sales representative or agronomist.
The seed of some crops can escape harvest, germinate the following year and become "volunteer" weeds in a rotational crop. This can happen regardless of whether the crop seed was herbicide tolerant or not. Many tools are available for managing herbicide tolerant volunteers, but advanced planning is advised to provide the greatest flexibility and success. The best strategies for managing herbicide tolerant volunteers are crop rotation, rotation of herbicides and rotation of herbicide tolerant traits. Properly adjusting harvesting equipment, cultivation and tillage management will also help reduce volunteer plants from previous crops. Plan at least a year ahead when planting a herbicide tolerant crop to make sure you have a weed management plan that will control any herbicide tolerant volunteers using alternate herbicide mode-of-action families and/or tillage for the next crop.
Possible indicators of weed resistance to herbicides include achieving good control of all but one of the labeled weed species in the field by the herbicide and/or failure of repeated applications of the same herbicide to control only that weed species in a field. Be wary that weed control failures can have many causes not related to herbicide resistance. Lack of rainfall to activate pre-emergence herbicides, rainfall right after post-emergence applications washing the herbicide off the plant, cool temperatures, slow growth reducing herbicide activity in the plant, improper application timing, or improperly calibrated application equipment are among the many causes of less than expected herbicide performance. If you suspect a weed control failure is caused by weed resistance to an herbicide you should first contact your herbicide retailer or herbicide manufacturer's representative, and your local Pioneer agronomist, and conduct a thorough investigation that can eliminate other more common causes of poor weed control. Your local Pioneer agronomist will assist you with the additional steps that will be required if weed resistance to the herbicide is believed to be the issue.