Uncontrolled weeds in corn can use water and nutrients and negatively affect yields. (Texas A&M AgriLife photo by Kay Ledbetter)
Amarillo, TX (December 12, 2018) - While producers may find newer corn herbicides on the market, it is important to look herbicide performance under regional environmental conditions before making any large purchases, said a Texas A&M AgriLife Extension Service specialist.
There are many good herbicides on the market, but producers often find that some herbicides perform poorly under stressful Texas High Plains conditions, says Dr. Jourdan Bell, AgriLife Extension agronomist in Amarillo.
Bell said there were many good tank-mix options providing very good control, based on results from this year’s corn herbicide trials near Bushland. However, she reminded producers that coverage is a key component. For corn herbicides, treatments were applied at a rate of 15 gallons per acre.
“In our corn herbicide trials at Bushland, application volume in addition to proper herbicide selection was the key to success,” she says. “If we dropped the label guidelines of 15 gallons per acre; we often dropped success.”
The herbicide resistance seen across the High Plains states in both kochia and pigweed is, in part, due to less than maximum coverage over the years that left behind some weeds that built up the resistance, Bell says.
Another important consideration is the activation requirement of soil-applied herbicides, Bell says. Some chemicals need to be activated with a half-inch rain or irrigation while other herbicides may need up to 1 inch of rain or irrigation; the exact amount of water needed is a function of the herbicide’s water solubility.
“While this is not a problem on irrigated acres, this can be a problem under limited irrigation and on dryland acres if precipitation is not received in a timely manner,” she says.
Palmer amaranth, tumble pigweed, kochia, and Russian thistle are some of the weeds evaluated in the study, where multiple products with multiple modes of action are being tested, Bell says.
“Herbicides can be extremely expensive, so it is important that AgriLife Extension has the opportunity to evaluate newer herbicides under our environmental conditions and then be able to share that data with you,” she said.
While herbicides can be a significant production expense, it is important for producers to recognize the economic return on their herbicide investment, Bell says.
“Producers continually hear that weeds are using water and nutrients,” she says. “In our corn herbicide trials, we have evaluated yields between different treatments. We’ve seen up to an 80-bushel-per-acre difference between a plot with well-controlled weeds and an untreated control plot due to the resources being wasted by weeds. That is significant, especially at lower corn prices and in a limited water environment.”
There’s not just one solution for a successful herbicide program in the High Plains, Bell says.
“A successful program generally includes herbicides with residual activities in addition to post-emergence herbicides with several modes of action,” she says. “Having several modes of action along with good coverage allows producers to be more proactive against herbicide-resistant and hard-to-control weeds.”
The entire list of products tested, control levels and rotational intervals can be found at https://tinyurl.com/cornherbicides.