The blessing of a wet 2015 is expected to bring the curse of a weedy 2016, said Dr. Jourdan Bell, Texas A&M AgriLife Extension Service agronomist in Amarillo.
The above average precipitation in 2015 prompted the growth of weeds and where those weeds were not controlled, they produced seeds that will germinate and likely result in heavy weed pressure this spring and summer, Bell said.
“We need to be proactive about weed control this year,” she said. “Weeds rob inputs – water and nutrients – from your soil that would otherwise be available for your primary crop. So we advise you to start clean and stay clean.”
Bell said there were many good tank-mix options in last year’s corn and sorghum herbicide trials near Bushland that provided very good control. The trials demonstrate that good coverage is important for both pre- and post-emergent herbicides.
For corn herbicides, treatments were applied at a rate of 15 gallons per acre, and for sorghum herbicides, applications were made at a rate of 10 gallons per acre, she said. Both corn and sorghum herbicide plots were sprayed with flat-pan nozzles.
“You really want to make sure the herbicide is getting where it needs to be,” Bell said.
Soil type can also play a role in the efficacy of the various chemicals, she said.
“For example, we found very good control and no crop injury with Lumax applied as a pre-emergent in grain sorghum, but we are on a clay loam soil. On a coarse soil with low organic matter, this would not be recommended.”
In corn, there are many effective options for weed control, Bell said. However, the vast number of options can often be overwhelming.
“Producers don’t call only about one chemical; they are often inquiring about tank-mix options, potential application costs, timing of application and even rotational concerns,” she said.
“In our corn herbicide trials at Bushland, we had the opportunity to evaluate products from AMVAC, Bayer, DuPont, Dow, FMC and Syngenta,” Bell said. “These trials provide us an opportunity to evaluate herbicide performance and efficacy under regional conditions. We evaluated some very intensive herbicide programs as well as some simpler options.”
She said on limited tillage acreage, producers are aware of the importance of a solid herbicide program, and they are ready to adopt an intensive herbicide program. However, on tilled acreage, producers often have different concerns.
“While there is not just one solution for a successful herbicide program in the High Plains, a successful program generally includes herbicides with residual activities in addition to postemergence herbicides with several modes of action,” Bell said. “Having several modes of action along with good coverage allows producers to be more proactive against herbicide-resistant weeds.”
The price of chemical and application can vary widely, so she advised producers to make sure they target their treatments to get the most bang for their buck, she said. This includes the application rate as well as proper adjuvants to enhance herbicide activity.
“To avoid crop injury, it is always recommended producers read labels and follow application guidelines, including rotational restrictions, to avoid potential crop injury,” Bell said.
Another important consideration is the activation requirement of soil-applied herbicides, she said. Some chemicals need to be activated with a half-inch rain or irrigation, but 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 on dryland acres if precipitation is not received in a timely manner,” Bell said.
“With lower commodity prices, many producers try to cut herbicide costs,” she said. “But, it is important to remember that the weeds can rob resources from your crop and in turn hurt yields.”
As producers evaluate their inputs, it is important they consider cost-effective herbicide options rather than doing nothing, Bell said.
“Neglecting weeds in 2016 will magnify weed problems for years to come. Start clean, get a handle on the weeds before they get out of control.”