Weeds resistant to herbicides are a lifestyle for farmers, another concern to complicate an already complicated manufacturing system.
However choices exist not solely to handle resistance but in addition to scale back the dimensions of the weed seed financial institution.
“Resistance is here to stay,” stated Adam Hixson, BASF technical service consultant for Texas, Oklahoma, and New Mexico, throughout a latest media replace on managing herbicide resistant weeds within the Southwest.
Adam Hixson, BASF technical service consultant for Texas, Oklahoma, and New Mexico. (Picture by Shelley E. Huguley)
“We’ve heard the expression, ‘out with the old and in with the new,’” Hixson stated. “I want to change that to ‘in with the old and in with the new.’”
Again to fundamentals
Getting again to fundamentals, he stated, is essential to managing herbicide resistant weeds. He known as on Texas A&M AgriLife Professor and Extension Weed Specialist Pete Dotray to place the issue in perspective.
“According to the International Survey of Herbicide Resistant Weeds, we have eight resistant weed species in Texas,” Dotray stated. “The first case of resistance in the state was noted 30 years ago, but in the last 10 years, glyphosate resistance has created a lot of concern.”
Dotray stated Roundup resistant Palmer amaranth, also referred to as pigweed and carelessweed, was first recognized on the Texas Excessive Plains about 10 years in the past, later than in some Mid-South and Southeastern states. He believes a key to that late arrival was that Excessive Plains farmers by no means deserted residual herbicides, particularly the yellow herbicides like Treflan and Prowl.
Texas A&M AgriLife Professor and Extension Weed Specialist Pete Dotray (Picture by Shelley E.Huguley)
Overuse of Roundup, utilizing the identical chemistry time and again, and use of fewer herbicide and tillage inputs supplied an open door for the rise in resistant weed populations, Dotray stated. “Resistant weeds were likely already out there in extremely low numbers.”
Palmer amaranth resistance has difficult weed management, Hixson added. “We’ve seen multiple applications of glyphosate at labeled rates fail to control Palmer amaranth.”
He stated cures embrace guide management, resembling hoeing, which is pricey and time-consuming. “Also, we’re always looking for that next ‘shiny object’ that will solve the problem.”
Shiny issues have been scarce in recent times, nonetheless, so Hixson presents a unique choice. “We need to use what we have today, but use it in a more calculated, knowledge-based approach. We have to get back to the fundamentals of weed control.”
12 months-round effort
He and Dotray agree that profitable weed management methods don’t focus solely on in-season herbicide purposes. “Good weed management has to be a well-planned, year-round venture,” Hixson stated.
Weed identification is a precedence. “It’s important to identify the weeds and to understand fully the biology. Know when specific weed species are most vulnerable.”
He defined that Kochia, generally “a huge problem and resistant to several herbicides,” emerges early within the spring and sometimes has just one flush. An efficient residual herbicide, utilized on the proper time, will deal with most Kochia points.
Palmer amaranth, nonetheless, emerges from early within the season properly into fall and requires a season-long management program.
Dotray stated Palmer seed that emerge late within the season stay a menace to replenish the seed financial institution and create issues for the subsequent crop yr.
“We’ve looked at the abundance of seed one plant can produce,” he stated. “Palmer that emerges early produces as many as 500,000 to 600,000 seed, maybe more, per plant. That’s a lot of seed. But a Palmer plant that emerges in August will still produce as many as 20,000 seed, also a lot. As late as September, emerging plants will produce 2,000 seed, and still hundreds by October. Even plants that emerge as late as November can produce some viable seeds.”
“Leaving just one plant,” Hixson stated, “could add to the weed seed financial institution, a key issue for the subsequent season. One seed per sq. inch represents greater than 6 million seeds per acre.” So, subsequent season’s weed management ought to begin earlier than this season ends.
Dotray stated latest analysis exhibits a bit of excellent information in regards to the longevity of Palmer seed. Research have proven that some weed seed will retain viability for so long as 120 years.
“We had no good answer for how long Palmer seed remain viable, so five years ago we set up a test to see. We buried Palmer seed at various depths across the state.”
They uncover them at intervals, starting at six months, once more at 12 months, and yearly after that. Based mostly on knowledge from the primary 48 months of the analysis, “Palmer seed viability begins to decline significantly after 12 months. Those findings were the same across all locations and at all depths. A second study initiated in 2018 has shown the same results so far,” Dotray stated.
“The good news is that a farmer who does a good job of managing Palmer amaranth effectively with a systematic program can get them down to a manageable level in a short time.”
That system ought to embrace late purposes to forestall escapes, he stated.
Information is essential
Hixson stated an efficient weed management program additionally depends upon understanding not solely the weed species vulnerabilities but in addition the interactions of soils and chemistry.
He stated utilizing herbicides with a number of, efficient modes of motion needs to be a crucial a part of weed management
“But also understand the properties of the herbicides and how they respond to different conditions, including soil types and moisture. Soil leaching properties will affect herbicide efficacy,” he stated. “Also, the more water soluble a product is, the deeper it will move into the soil profile. Less soluble usually means more soil binding.”
He stated completely different soil sorts — modifications in clay content material, sand, natural matter degree — all could have an effect on herbicide exercise.
He stated in conditions with good moisture, a product like Zidua could possibly be the best choice. “In dryland or subsurface drip irrigation conditions, Outlook would be ideal.”
They key’s understanding the weed, the setting, and the herbicide properties, then utilizing the right materials for the goal weed underneath these particular situations.
Timing and protection
He added that software timing and protection additionally matter.
“Also remember, the cottonseed trait package you plant determines the herbicides you can use.”
“Using residual herbicides, identifying weeds and understanding the difference in solubility and where a product fits best based on soil and moisture are critical to a systems approach to weed management,” Dotray added.
In response to a query about new dicamba labels, Hixson stated BASF wouldn’t veer from the necessities established by the federal label in Texas, Oklahoma, and New Mexico
Dotray famous that the new registrations come with some important modifications, together with greater buffers, volatility discount adjuvant necessities and software timing.
“Also, last year some states used 24-C exemptions to alter some regulations. So far this year, states that have applied for a 24-C have been denied.”
Hixson introduced that BASF does have one “shiny object” within the pipeline, a new seed trait with tolerance to 4 herbicides –GLIXTP, pending regulatory approval. He anticipates introduction in 2023, with doubtlessly extra availability in 2024.
Within the meantime, he stated, “Old chemistry still has value.”