Farmers are notorious for not believing that they can learn from farmers in another state, but the spread of herbicide-resistant weeds is changing that mind set.
Turk Regennitter, general sales manager for Merschman Seeds with headquarters in West Point, Iowa, said the seed company has had a “large presence in the bootheel of Missouri where serious weed resistance has occurred. We watched the pigweed resistance grow from its infancy in that area to being a major problem in many states.”
“We felt it was our obligation to our customers (in seven states) to forewarn them about what was coming and the changes that would be needed to be made to preserve any technology,” Regennitter said.
When the seed company representatives started talking to farmers outside the bootheel, the reaction was “those guys down south don’t really know how to farm like we do up here.” But the reality is that farmers north and south have to grow soybeans using similar methods and products to counter glyphosate-resistant weeds in soybeans, the Merschman representatives have countered.
The similar control system is for a pre-emergence herbicide followed by a postemergence herbicide when escaped weeds are small, no larger than four inches. In the last couple years, it has become easier for Merschman Seeds to recommend the easiest and preferred answer because they have had an increasing number of LiberyLink soybeans, which allows the use of Liberty herbicide. LibertyLink soybeans are being sold by more than 100 seed brands nationwide, today.
The herbicide sprayed over LibertyLink soybeans will not damage the beans and is proven to kill the wide spectrum of glyphosate-resistant weeds. Regennitter noted that the company sells soybean seed in the maturity ranges of 1.8 to 5.4 with LibertyLink seed available in most of this maturity range.
Timing of a Roundup application was a minor concern until weed resistance started showing up, but any postemergence application, including glyphosate, is now only recommended to kill small weeds. Turk said, “Two-inch tall weeds is what we want our customers spraying.”
Alan Hopkins, Bayer CropScience Midsouth area seed technology manager, said, "We strongly encourage growers to target young actively-growing weeds. This will provide the most consistent weed control performance. Achieving maximum weed control and using herbicides with multiple effective modes of action, including residual herbicides, will reduce the risk of weeds becoming resistant to Liberty herbicide."
As Hopkins noted, glyphosate was often applied when weeds were outside the recommended size, and those escaped weeds were part of the start of glyphosate weed resistance. With this in mind, Bayer CropScience wants to assure its seed and herbicide technology system is maintained as effective.
“Early timing is not only great for effective control of weeds, but also making sure that we don’t put Liberty herbicide under unnecessary selection pressure by targeting weeds that are too large,” he said.
Regennitter said, “I can remember when universities were first talking about chemical weed control as opposed to cultivation. They used the wording of economic threshold to talk about how many weeds could be left in a field. Today, the economic threshold is zero because you cannot have any weeds growing out there because they will eventually be resistant to the herbicides being sprayed. We’ve seen it happen.”
Hopkins added, “Removing all the weeds while they are young and small will prevent competition and prevent the potential for yield loss, too.
Hopkins is extremely confident that the LibertyLink and Liberty herbicide weed control system with a pre-emergence herbicide down first is the “most effective and important system for every soybean grower.”