What is in this article?:
- Horseweed causing bigger headaches for cotton, soybean growers
- Not helping with cost-cutting measures
• In the decades when conventional tillage practices were the norm rather than the exception, horseweed was never a problem.
• The problem started when minimal-tillage cropping systems were introduced roughly a generation ago, both as a cost-saving measure and as a strategy for building up organic residue. Minimal-tillage provided the optimal conditions in which horseweed seed could germinate and grow.
Not helping with cost-cutting measures
However, in an era when cost-cutting is a paramount concern among producers, horseweed is causing plenty of grief, especially among the unfortunate handful of Tennessee Valley producers who are dealing with horseweed and pigweed.
“It may not be as big a problem as pigweed, but it’s still a problem,” Patterson says. “You’re not going to have the same sized populations with horseweed as you do pigweed because it doesn’t produce as many seed, but it’s still a problem considering that it can grow as tall as 6 feet.”
The part that concerns Patterson and Burmester alike is that the weed is undergoing a change in growth patterns.
“We’re talking about a weed that has historically been considered a winter annual that germinated in the fall and grew in the spring and that could be taken out by tillage,” Patterson says. “Now this weed is turning up during the summer in cotton and soybeans, especially those that are planted within minimal-tillage, Roundup Ready cropping systems.”
Several herbicides, particularly gramoxone and paraquat, mixed with diuron or valor and used in burn-down applications ahead of cotton, soybean and corn plantings are still effective.
So is the old stand-by, 2,4-D, as well as dicamba. However, timing is critical.
With 2,4-D applications for example, growers must wait a month to plant cotton to avoid crop damage. The wait for soybeans is considerably less — only a week, if the grower opts to apply a pint-per-acre of 2,4-D ester, but 2 weeks if the grower applies a pint of 2,4-D amine.
Growers should delay corn planting for a week following 2,4-D application.
Patterson says the use of glufosinate, with LibertyLink cropping systems, is gaining favor among some growers.
The critical issue, especially with cotton, Burmester says, is taking out the weed early — before it reaches sufficient size — for example, in the case of cotton, “kill ‘em before the crop emerges.”
“With cotton, for example, once the weeds are up, you don’t have many options,” Burmester says. “There’s nothing other than Liberty herbicide, which is only available with the LibertyLink variety.”
Burmester says he’s noticed many growers using a combination of dicamba and Roundup, though they’re reporting more problems compared with last year.
He says these problems have encouraged many growers to return to Liberty cropping systems, which, in addition to burning down the horseweed, carries fewer restrictions between spraying and planting.
Many growers still find 2,4-D effective, which is a good thing, Burmester says, because it ensures that more Liberty herbicide is held in reserve to deal with pigweed outbreaks.
“We just don’t want to put too much pressure on Liberty herbicide because of what we’re encountering with pigweed,” he says. “We don’t want to put too much pressure on it with over-use.”
(For reference, you might also want to read Management of horseweed escapes prior to planting).