This spring, I wrote an article about using dicamba and other pesticides responsibly. Farmers here in southeast Missouri and in many soybean-growing areas had struggled with symptoms of dicamba drift on their soybeans and other sensitive crops. This season, reports I have heard and articles I have read indicate that we did a better job of minimizing off-target pesticide impacts in 2018 compared with the past. We did have some help, though. The Arkansas State Plant Board banned dicamba use in the state from April 16 to Oct. 31, and Missouri banned its use after June 10 in southeast counties and after July 15 in all other counties. Applications in Missouri had to be made by trained applicators and occur between 7:30 a.m. and 5:30 p.m. There were many more restrictions and requirements, and they varied for every state. The Environmental Protection Agency told us in the spring that there would need to be significantly fewer complaints to justify extending the current labels for XtendiMax, Engenia and FeXapan, which are set to expire this fall. [Here’s the announcement from EPA on the dicamba label going forward]
What Else is There?
Farmers need more options for weed control. For post-emergence control of Palmer amaranth, we currently have two options other than dicamba. Glufosinate and fomesafen applications must both be used on very small weeds, and excellent coverage and appropriate application conditions are absolutely critical for success. Enlist corn and cotton are commercially available and appear to be good systems, though I personally have not seen these crops in large-scale production. As with dicamba, I am assuming that we won’t know what off-target issues may be observed until Enlist soybeans gain Chinese approval at some point in the future. LibertyLink GT27 soybeans will be available for 2019 in limited quantities. Their introduction will bring the first soybeans tolerant to both glufosinate and glyphosate. This trait package is also tolerant to the new HPPD/Group 27 herbicide, but that does not have full approval for use at this time.
Importance of Resistance Management
I recently hosted a participant from the NAICC Leadership Program. He is a consultant from Wisconsin, which is beginning to experience tall waterhemp herbicide resistance, and he knew southeast Missouri was a core resistant amaranthus area. We spent a good deal of time talking about resistance issues we have faced in the past 10 years to 15 years, and I mentioned I wished someone had told us back then to adopt a “start-clean, stay-clean” mentality concerning weed control. In those days, farmers would take off early, go to the lake, and wait until next week to spray. They knew a half rate of glyphosate would kill a 5' tall pigweed, and if they worked it right, then they might be able to get by with just one glyphosate application for the entire season. As I reflected on our past bad decisions and current three- to four-pass soybean weed control program, he told me I was describing the way many of his growers view weed control today. I did my best to show him the consequences of a reactive rather than proactive view of weed management.
In the past 10 years, attempts to bring new products to market have been met with obstacles that have delayed the availability of critical tools for farmers. It is clear we cannot rely solely on the promise of new products. Proper resistance-management practices are key to maintaining current and future weed control systems. As a result, emphasizing grower education is increasingly critical for the sustainability of modern agriculture.