The last couple of weeks were spent hoofing around the northern Delta in search of the perfect herbicide program for control of glyphosate-resistant Palmer pigweed. After talking to numerous soybean and cotton producers and weed scientists, I have found there isn't one.
The one system that was as close to perfect for weed control as you could get - glyphosate-resistant technology - no longer effectively controls the pernicious pest. Pigweed is becoming as ubiquitous as johnsongrass, cocklebur and morningglory were before glyphosate-resistant technology came along.
Mid-South weed scientists Larry Steckel, Ken Smith, Bob Scott and Delta Farm Press contributor Ford Baldwin believe the era of easy weed control is now officially over.
That's not to say that current weed control technology and cultural practices will not control pigweed. It can. But pigweed can grow from a susceptible 4-inch plant to a resistant 8-inch plant in a day and a half. An afternoon shower or a sudden change in wind direction or speed can ruin your timing, your weed control budget and your bottom line.
A weed control expert said that cocklebur was the most competitive weed he had ever seen “going head to head with another single plant.” But Palmer pigweeds overcome by sheer numbers.
I did see weed control programs that worked, most of them pairing residual herbicides with herbicide-resistant technologies. The residual widens the margin for error enough to where producers can feel a little less anxiety about their futures.
But these systems will demand more management from growers. Post applications have to be made on small pigweed.
Perhaps the most insidious side effect of resistant Palmer pigweed has been its effect on conservation tillage.
Arkansas weed scientist Ken Smith is concerned about a notable decrease in conservation tillage due to farmers having to pull out the plow for resistant pigweed.
As we all know, glyphosate-resistant technology helped to usher in the era of conservation tillage, which reduces soil loss, allows producers to farm more land with less labor and could be the cornerstone for new climate change policies involving agriculture.
New weed control technologies with resistance to multiple herbicides are on the way, which will help, and some farmers are dusting off their hooded sprayers. The Natural Resources Conservation Service is also becoming aware of pigweed's threat to conservation tillage and perhaps could be urged to develop incentives for farmers to reconsider the tillage option.
In the meantime, weed scientists are urging farmers to use residuals in their weed control programs, and to remember that the key to success of an entire season may come down to whether you made an post application on 4-inch pigweed or 8-inch pigweed.