A recent spell of hot weather in parts of rural America has led to some questions about timing for herbicide applications in soybeans. Dr. Rodrigo Werle, an associate professor of weed science at the University of Wisconsin, talked about his recommendations for spraying when it’s hot.
“So, we have a crop that is actively growing. We have a problematic weed out there that’s called water hemp. A lot of our farmers are dealing with and struggling to manage this weed, and this weed just loves the weather that we’re dealing with this week, where we have plenty of moisture in the soil and heat. A lot of heat, so this weed is going to grow fast. So, we’re telling growers that they’ve got to be pulling the trigger. Otherwise, if we wait another week here or so, these weeds are going to be too tall. We’re not going to be able to manage them.”
However, crop injury will be a bigger concern in hot weather.
“However, when we’re spraying under warm conditions, such as what we’re dealing with, crop injury becomes a big concern. So, I’m walking our growers through the scenario. Some of them already put a post-application out about a week or ten days ago, and I’m telling them, go out there and monitor those fields. If you got a good control of the water hemp, you’re set, but if you are seeing some escape, some regrowth of the water hemp, they still have an opportunity to do a re-spray, just so we don’t let those weeds produce more seed at the end of the year and make problems worse for the future.”
Werle offered his recommendation.
“And the main recommendation for the few that need a re-spray would be to use glufosinate, also known as Liberty Herbicide. So, there’s a five-day window between applications, but the catch there is the Liberty must be sprayed before soybeans are at the R1 stage, so growers have to monitor the crop growth stage and whether weeds are regrowing, and they have an opportunity for a re-spray scenario.”
He talked about farmers who may be deploying their first post application.
“For the farmers that are now deploying their first post application, this is probably going to be the one-and-only post application now. Hopefully, that’s the scenario for most of the farmers out there. They had a good pre-. The pre provided good control, so now it’s time for post. Our standard recommendation here – I’m talking about Enlist E3 soybeans, because that’s the genetics that most of our growers are cultivating – is going to be Enlist plus Liberty. So, we have the two herbicides together. We need to make sure we have enough AMS, ammonium sulfate, in the tank for the Liberty to work.”
More information on his recommendations can be found at badgercropnetwork.com.