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Herbicide Tolerant Crops and Weed Management

Note: DuPont scientists conducted a review of current scientific literature about the impact of biotechnology on crops and weed management. This information will be updated from time-to-time. We welcome new scientific information and, of course, your perspective.

Growers must control weeds that compete with their crops for water, nutrients and sunlight. A number of options for minimizing the impact of weeds on crop productivity are available to growers: one option is the application of herbicides.

Virtually all crops have some degree of innate tolerance to some herbicides but not others. In the 1940's, this selective tolerance started to be used to control weeds in corn fields. Today growers all over the world minimize the negative impact of weeds by using herbicides and herbicide tolerant crops, including all of the major commodity crops, as well as small acreage horticultural crops, such as vegetables.

An ancillary benefit of herbicides is the impact their use has on soil erosion. The use of herbicides and herbicide tolerant crops enables growers to use minimal tillage or no-till techniques, which significantly decreases the impact of agriculture on soil erosion.

Since the 1990s herbicide tolerant crops, developed with modern biotechnology, have significantly increased growers’ profits by decreasing their input costs, increasing yields, or both, in some cases as well as save soil from erosion.  As a result of these benefits, the rate of adoption of biotech herbicide tolerant crops has been quite rapid. For example in Argentina glyphosate-tolerant soybeans were planted on over 98% of soybean acres within 5 years of introduction.

Where any single herbicide is used repeatedly, the development of resistant weeds and weed shifts can occur more rapidly.  In most cases where herbicide resistant weed biotypes occur, the same herbicide can continue to have utility due to the spectrum of weeds present. To control the herbicide-resistant weed, weed scientists recommend adding another herbicide to the primary herbicide.  A common tactic of growers to manage the evolution of resistant weeds is using mixtures of herbicides with different modes of action and overlapping weed spectrums.

Generally, the best approach to resistance management is to use Integrated Weed Management (IWM) practices.

The most important principle of weed resistance management is to prevent the survival and spread of resistant populations.  The key fundamentals are:

  1. Use an effective alternate mode of action (MOA) to control known herbicide-resistant weeds
  2. Include effective alternate MOA at least every-other year for “at-risk” weeds
  3. Scout fields to monitor effectiveness of the herbicide program

The following are additional considerations growers should choose to incorporate into their farming practices to manage weed resistance:

  1. Utilize herbicides with multiple modes of action effective on target weeds, including those with residual, before glyphosate applications and/or tank-mix another herbicide with glyphosate.
  2. Utilize cultural practices such as cultivation, other mechanical weed management practices or crop rotation.
  3. Apply herbicides at labeled rates and at the recommended stage of weed growth as stated on the label.
  4. Seed genetics should be selected based on agronomics, desired traits and yield potential.
  5. Purchase of an herbicide-resistant hybrid or variety does not limit the grower to use only one herbicide system. Conventional herbicides can and should still be a part of the grower’s overall weed management system.
  6. Growers utilizing herbicide programs with herbicide tolerant crops can do so on an annual basis provided the technology is managed effectively.
  7. Fields should be scouted before and after herbicide applications.
  8. Equipment clean out is essential to reduce the spread of resistant weed seed.

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