Changes are needed for weed control management practices in corn and soybeans across the Midwest. Palmer amaranth (Amaranthus palmeri) has established itself across the state. Sure, we've battled fellow pigweed species for years, but this new one with its rapid growth is a game changer.
Recently, I had the pleasure of attending a field research tour sponsored by Bayer CropScience. I've attended similar field day events in the past and had no reason to think this one would be much different. My expectations of joining no more than 30 others were exceeded when between 400 and 450 showed up! In fact, the hosts were caught a bit off guard by the record attendance. One representative commented that about 250 had preregistered. That many unexpected participants were a bit of a problem with catering….but overall, it was a GOOD problem because it was abundantly clear that producers have realized this new weed is in their area and they came to learn what this is going to mean for current management practices on their farms.
The tour featured four presentations by weed scientists from the University of Illinois and the University of Tennessee as well as a representative of Bayer CropScience. They gave tips on identification of Palmer amaranth. They discussed herbicide resistance among waterhemp and Palmer amaranth populations. They told stories of how this weed had devastated crops in southern states. Not only crops, but farms have been lost to this extremely competitive weed. Lastly, they gave recommendations on management.
This last part really resonated with me. I was reminded that nothing is constant but change. Now some practices will be the same. There is a big emphasis on scouting with this new weed. Fields were scouted before, but now the practice will be amped up considerably where populations are suspected or known. Weed size was always important but now it is critical. Post-emergent applications must be made to small plants. Soil residual herbicides must now be used. They used to be common, but glyphosate alone did such a fabulous job. It was easy and the price was right. We rode that train as long as we could. However, using multiple modes of action and rotating chemistries are of extreme importance in keeping Palmer amaranth controlled. In fact, one speaker noted that using a single chemistry was just stupid. Yet, that was the common practice for years.
Two thoughts came to mind with that comment. One was the time in grad school when I asked if we'd ever see weed resistance occur with glyphosate and I was laughed at and told, "No, we would have seen it by now." That was roughly 16-17 years ago. We know better now. The other thought that occurred to me is, "What practices are we using now that in 16-17 years will no longer be recommended?" We will continue to conduct research and learn and amend recommendations and practices as needed. That's what humans do no matter the topic or area of concern.
Many in the crowd yesterday had questions and concerns such as, "Will I spread the seed from here to my farm? Would it get stuck on my boots or clothing, or fall into the information bags we were given?" There were jokes of setting fire to clothing and boots before returning home. How many left the tour and went directly out to take a closer look at the suspiciously fast growing pigweed patches in their own fields?
The comment was made by one bystander that producers will need to sit down and make a multi-year plan of their management strategies. He thought four years would be good. His recommendation made sense, but how many will do this and do so right away? Producers want to use products that are effective, easy, and inexpensive.
It's not as simple as rotating between corn and soybeans from year to year. There are herbicide tolerant crops on the market and coming to the market within a few years that offer improved flexibility for growers. But they must be used wisely and planning will be needed so that the herbicide mode of action is rotated. The use of tank mixes with multiple modes of action will be vital in controlling Palmer amaranth. Weed control costs are expected to rise to $100 per acre for soybeans and $60-70 for corn. Ouch!
Other less commonly used methods of control were discussed as being effective options for this weed. Many have sold their field cultivators with the reduced need for them in past years, but cultivators may be making a comeback, as is hand removal in the form of "walkin' beans." Speaking from much personal experience, the latter is an unpleasant job – even if you are working for only one night out that involves pizza and a trip to the movie theater once all of your dad's fields are weed free. I do hope most kids get paid better these days. For more information on what "walkin' beans" involves, check out this article: http://www.farmtalknewspaper.com/local/x197375941/Walkin-Beans
The field day presenters had maps showing the Illinois counties where Palmer amaranth has been documented. They noted, too, that they have no reason to believe that this plant is not already in every county. How long it will take for this weed to spread beyond the agricultural fields into natural areas and other landscapes where it will completely take over in a short amount of time? My recent Home, Yard, and Garden article raised some of these concerns: http://hyg.ipm.illinois.edu/article.php?id=609. Currently, Palmer amaranth is not listed as a Noxious Weed in Illinois, but other states have listed it as such.
It was noted by one speaker that seeds are spread by wind, but birds also assist in spreading Palmer amaranth seed. The site of the tour is that of an old landfill and has no shortage of birds; sea gulls are common visitors. Just south of the research plots is a landscape waste compost facility. All morning, trucks entered and left via the rock road bordering the research farm. I can't help but wonder how much Palmer amaranth seed was in that compost and were it will eventually end up.
In other good news, neighbor disputes are bound to happen when one is accused of not controlling this weed and allowing the seed to spread to neighboring property. Lawsuits will likely follow. Stories were shared of landlords that took away land from renters who were not managing this weed. Questions were raised by potential renters. Should they even consider renting ground with a known infestation?
Again, we know now that Palmer amaranth IS manageable with at least 3 herbicide application passes across the field. Watch the Bulletin (http://bulletin.ipm.illinois.edu/ ) for recommended control strategies and more information. Certainly, the game has changed a bit in how we keep yield-robbing weeds at bay and what it will cost.