⋅ BY CASSIDY NEMEC ⋅
ASSOCIATE EDITOR
Finding the right timing when it comes to cotton weed management can be tricky. Weather, soil type and many other environmental factors come into play. Kaelin Saul, BASF technical service representative for Louisiana and Mississippi, said timing plays a key role in weed control.
She recommends going behind the planter with a residual product before coming back with postemergence applications in order to overlap residuals for overall better weed control. “The easiest time to control a weed is before it actually comes out of the ground.”
Saul said preemergence herbicide applications of Prowl H2O, Cotoran or Brake can be good options to ensure you are beginning the season with clean fields. Following with POST applications of residual herbicides, such as Zidua SC and Outlook, help extend season-long weed control.
Zidua SC And Outlook As Residual Options
Two residual POST herbicide options are Outlook and Zidua SC. According to Saul, Outlook requires less rainfall activation at just around one-quarter of an inch. “If your region doesn’t receive much rainfall or you have dryland cotton with little chance of rain in the forecast, Outlook would be a good residual herbicide to throw in the tank with your POST application.”
Zidua SC has two different application methods: post-directed or layby applications and impregnation on fertilizer.
“While layby applications are not new, there is a new drop-nozzle program this year to help growers with purchasing drop nozzles for their sprayers,” Saul said. “These drop nozzles are more rigid than typical layby equipment and allow growers to cover more acres in less time. The drop nozzles help get underneath the cotton canopy to make sure the product is making it to where it needs to go. Impregnation of Zidua SC on fertilizer provides another option for areas where the drop nozzles might not be an option, like hilly fields.”
For impregnation, Saul recommends using 250 lbs. per acre of fertilizer, which can be a blend, to give the best coverage.
Both application methods allow Zidua SC to be applied from 5-leaf to beginning bloom. Saul said this provides flexibility to get Zidua SC on the cotton acre.
Zidua SC requires half to three-quarters of an inch of rain or irrigation for activation. “Even though Zidua requires more to be activated, it does not degrade under sunlight like some other Group 15 herbicides, so it can wait longer for that activating rainfall,” Saul said.
Depending on environmental conditions, she said they see extended residual control with Zidua SC.
Other Factors
If a big storm comes through after an initial residual application, Saul said the state of the weeds in the field and time of year can play a big role in determining next steps.
“If it’s the heat of the summer and a storm rolls through, bringing with it a flush of weeds, that’s going to be a time to follow up with another herbicide application using a POST, such as Liberty or Roundup, with a residual in the tank to control the emerged broadleaves and grasses and hold back the weeds from re-emerging before the cotton has a chance to canopy.”
Engenia and Liberty are some other postemergence product options. Saul said the limited Engenia supply still out there is a good option for dicamba-tolerant cotton.
“Outlook is great as it tank mixes well with Liberty and makes it a bit hotter to kill broadleaf pigweeds you don’t want, especially weeds hardened from environmental stress.”
Overall, Saul said for water volume, they recommend 20 gallons of water per acre, especially with Liberty. “With Liberty being a contact herbicide, we want to make sure we are getting really good coverage. By layering residuals, we can protect our yield potential and provide effective weed control of broadleaves and grasses, which is one way we can manage weed resistance to herbicides.”