The Environmental Protection Agency (EPA) sent out a press release announcing a decision to register a new herbicide that contains two active ingredients, 2,4-D and glyphosate. These two ingredients are the most widely used herbicides in the world for controlling weeds. Local gardeners use 2,4-D to kill dandelions in lawns and glyphosate to kill just about anything green. This new herbicide combo is designed primarily to kill weeds in corn and soybeans; crops that have been genetically engineered to tolerate both chemical compounds.
EPA scientists used conservative assessments to evaluate not only the human health risks, but also the ecological risks. The agency evaluated the risks to all age groups, from infants to the elderly, and took into account exposures through food, water, pesticide drift and as a result of use around homes.
The decision meets the rigorous Food Quality Protection Act standard of “reasonable certainty of no harm” to human health. The assessments confirm these uses meet the safety standards for pesticide registration and, as approved, will be protective of the public, agricultural workers and non-target species, including endangered species.
While genetically engineering plants to tolerate chemicals that would normally kill them allows farmers to kill weeds more easily, weeds quickly build up resistance to new herbicides. In a few years, the herbicides no longer work to control weeds in the crop and new chemicals must be created or combined and additional genetic engineering must occur. Resistant weeds become quite costly to a farmer, who no longer can use that method of control. Those costs are usually passed on to the consumer.
To ensure that weeds will not become resistant to the 2,4-D/glyphosate combo, EPA is imposing a new, robust set of requirements on the company registering the product. These requirements include extensive surveying and reporting to EPA, grower education and remediation plans. The registration will expire in six years, allowing EPA to revisit the issue of resistance. In the future, the agency intends to apply this approach to weed resistance management for all existing and new herbicides used on herbicide-tolerant crops.
Although this combination herbicide may not be registered for use in Nevada in the near future, home gardeners, farmers and others use many other herbicides. Overuse of any herbicides or repeated use of the same herbicide can create resistance in the common weeds we deal with in Nevada. Use herbicides as a last resort. If you do apply herbicides, use products with different active ingredients each year to avoid creating resistant weeds.
JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension and may be reached at skellyj@unce.unr.edu or 775-887-2252.