Man Vs. Weeds

Often Tillage, Rotation Needed To Overcome Weed Infestation

BETTY VALLE GEGG-NAEGER
MidAmerica Farmer Grower

BELLEVILLE, ILL.
    The challenges of weed management in today’s production systems were the topics of discussion for Dr. Bryan Young,   Professor of Weed Science/Agronomy in the Department of Plant, Soil and Agricultural Systems at Southern Illinois University.   He compared weed management with the change in production systems and how the methods have evolved over time.


Dr. Bryan Young, Professor of Weed Science/Agronomy in the Department of Plant, Soil and Agricultural Systems at Southern Illinois University, discusses the challenges of weed management in today’s production systems.
Photo by John LaRose, Jr.

    “We’ve used a lot of mechanical tillage and man and human power to manage our weeds throughout history, and then we’ve gravitated more towards using tractors and cultivation, and now chemicals and genetically modified crop traits that we’ve been utilizing such as the Roundup Ready system,” he explained. “It’s been a continual evolution of how we manage weeds but it’s been really gravitating mostly to chemicals. That’s where the challenge comes because we’ve reduced our dependence on some of the other weed control methods, such as mechanical and cultural control methods, and we’ve gone more towards chemical weed control. The advent and use of herbicides has been extremely positive for modern agriculture, but it has been the departure from other control methods that has created our primary challenges with weeds today.”
    These practices have brought with them an increase in herbicide resistant weeds. Young emphasized the amount of herbicide resistant weed infestations occurring today.
“Throughout the vast majority of counties in Illinois are waterhemp biotypes with resistance to multiple herbicide modes of action,” he said. “This is of particular interest because if we just had weeds resistant to Roundup, glyphosate products, that would be one thing; but waterhemp is also resistant to some of the older herbicides that we use in an attempt to control weeds that glyphosate won’t kill. Thus, it’s the multiple herbicide resistance to older herbicides that has previously existed in our fields and now we added glyphosate to it. That’s one of our biggest challenges, we’re running out of some herbicide options.”
    “I’ve been having phone calls like they’ve had in the Midsouth for Palmer amaranth, but in this case it’s for waterhemp,” Young added. “We’ve used a residual herbicide, we’ve used a glyphosate and another PPO-inhibiting herbicide post emergence, sometimes twice, and we have very little control of our waterhemp. What do we do?
    “If it’s early enough in the growing season the option is to till the field and plant soybeans again, he said. That’s been an issue in the south with cotton and soybean fields that had Palmer amaranth infestations, but it’s also now an issue in Illinois with waterhemp, at least in the southern portion of the state.
    “We don’t have any more post emergence options in glyphosate-resistant soybeans to rescue a field, they just aren’t available. So we’re looking toward the future, looking for future integration of new technologies to improve weed management; but in the meantime, farmers need to remain diligent and go ahead and utilize as many effective herbicides as possible to get multiple modes of action at these weeds, pre-emergence preferably, so the weeds never come up; then hopefully we will observe some more consistent control and successful management if we continue down that line,” he summed.∆
BETTY VALLE GEGG-NAEGER: Senior Staff Writer, MidAmerica Farmer Grower