INDIANAPOLIS — Waterhemp has a cunning way of adapting, with an emergence pattern that lasts throughout the summer and its ability to produce a large number of seeds. The survivability of the weed was demonstrated in recently released results from a University of Nebraska evaluation involving a grass field, where sequential treatments of an auxin herbicide over a 15-year period resulted in an isolated case of resistance.
The Enlist Weed Control System, under development by Dow AgroSciences, was designed with resistance management principles in mind and an understanding that nature (including the weed control landscape) will always adapt; effective weed control technology must be ready to handle its many changes. Pending regulatory approval, the Enlist system combines herbicide tolerance traits that will enable the use of glyphosate, glufosinate (in soybeans and cotton), and FOP chemistries (in corn) as well as new 2,4-D choline, to combat a wide range of weed pressures.
“If you can control a weed with two or three mechanisms of action, the likelihood of resistance occurring to all the mechanisms used is greatly reduced,” said Steve Weller, horticulture professor, Purdue University.
The Enlist system will provide tolerance to Enlist Duo™ herbicide, which is a proprietary blend of glyphosate and new 2,4-D choline. Additionally, the system was designed to be used in a program approach with a foundation herbicide treatment such as SureStart® herbicide in corn and Sonic® herbicide in soybeans to use a total of four modes of action in one season.
“It’s known that plants adapt, and weeds are no different,” says Mark Peterson, global biology leader for the Enlist Weed Control System. “Years of research in weed science have demonstrated that continuous use of a single mode of action will ultimately result in the development of a resistant population. If a single weed management practice is used continuously, resistant weed biotypes are likely to arise.”
In the Nebraska evaluation, seed was collected from a grass field that received sequential treatments of the auxin herbicide 2,4-D up to twice a year for 15 years. Greenhouse trials conducted this year determined the waterhemp populations developed auxin herbicide resistance because of the tremendous pressure exerted on a single mode of action over a period of many years. The report also concluded that the auxin-resistant waterhemp population is isolated.
“In looking at this specific field, the importance of multiple modes of action is very clear,” says Greg Kruger, cropping systems specialist, West Central Research & Extension Center, University of Nebraska-Lincoln. “It is unrealistic to expect any herbicide that is used exclusively for an extended period of time to not come under some pressure.”
Peterson adds that the Nebraska evaluation reinforces the need for rotating chemistries and using multiple modes of action. The Enlist Weed Control System will be part of a program approach with the recommendation to start with a foundation herbicide.
“With the Enlist™ system and the program approach, growers will be able to keep farming the way they prefer and have renewed confidence in their herbicides,” Peterson says. “Use of multiple modes of action within one system helps growers to maintain effective weed management and efficient crop production.”