Friday, April 12, 2024

Top 5 Common Weed Problems

Time, thought and awareness can help prevent many problems with weed management.


Reduce Weed Management Errors: • Be as timely as possible. • Lower boom height, reduce speed to improve coverage. • Throw away all empty pesticide jugs. • Do not pour new chemicals into empty jugs for mixing. • Look in the tank to be sure it is clean. • Train employees to not make assumptions. • Improve awareness of off-target movement, other problems. • Put fields with broadleaf perennials into a crop other than peanuts first. • Protect pesticide modes of action because new ones are not coming.

It was Marcus Tullious Cicero, a statesman, lawyer and philosopher whose principles led to the establishment of the Roman Empire, who possibly first wrote, “Man is his own worst enemy.” It has been so before, during and ever since that time. People are often the cause of many of their own problems. That could be why University of Georgia Extension weed specialist Eric Prostko focused his talks this spring on preventing self-inflicted weed management issues.

We all make mistakes, Prostko says, but putting a little more time, thought and awareness into some situations could prevent potential problems.

What Are The Problems?

Wondering if the problems faced by he and UGA Extension cotton weed specialist Stanley Culpepper last year were similar to those faced by other weed scientist colleagues, Prostko did an informal survey.

“I polled my colleagues across the Southeast from Virginia to Missouri and asked them to rank these five problems that are common for me on a scale of one to five,” Prostko says.

The most common problem for the 21 Extension weed scientists who responded was off-target movement, followed by sprayer tank contamination, mixing and jug errors, herbicide carryover look-a-likes, with true herbicide carryover as the least-common problem.

Prostko says these rankings were different than what he would put forward.

“My No. 1 was mixing and jug errors, followed by herbicide carryover look-a-likes,” he says. “Culpepper said herbicide carryover look-a-likes followed by sprayer contamination, probably owing to the different systems used in cotton.”

With off-target movement not in the top spot, Prostko says he feels pretty good about the job they’ve been doing in educating growers about drift scenarios.

Start On Time

More than anything, Prostko says getting into the field on a timely basis could solve many problems.

“I know many farmers have more and more acres to cover, and it’s hard to get into those fields on a timely basis. But that said, almost every time we spray a herbicide at the right time, it is going to work,” he says. “When you are timely, things are going to go well.”

However, if you can’t be timely, coverage becomes more important.

Big, fancy sprayers are nice, he says, and it enables you to spray more, but are they perfect? Do we get the best coverage?

“Boom height and speed affects coverage,” he says. “I am 6 feet tall, and if your boom is that high, you are not getting good coverage, especially if you are also driving too fast.

“I’m not suggesting you drive 3 miles per hour, but if you are having problems getting good coverage and you are looking for ways to tweak how you spray, reduce that speed just a bit.”

Chuck Old Jugs

Going back to his No. 1 problem that is very preventable, Prostko says he wishes he could get all farmers to throw out any empty jugs laying around their shop.

“If you have an empty jug laying around, poke a hole in it and get rid of it. One of the main problems I see is contamination from reused containers. Something will get sprayed on peanuts that wasn’t supposed to because a chemical was put in an unlabeled container.

“Don’t put new chemicals into other jugs thinking you are going to remember what you did or will come back and label it later. Get rid of the jugs,” he says.

Practice Situational Awareness

Following closely with jug and mixing errors is simply situational awareness.

“As far as sprayer contamination and cleanout, look in the tank to make sure it’s clean. Don’t make assumptions, and don’t assume workers are taking care of it,” Prostko says. “Many times, I go into the field and the farmer isn’t the one doing the spraying. You need to make sure folks that work for you follow these points as well. Some growers use separate sprayers for different crops such as peanut and cotton.”

This point follows closely with off-target movement in that being aware of wind speed and direction and being aware of other, neighboring fields that may be affected can help reduce problems.

Education on these points and knowing what various problems are likely to look like can help farmers diagnose a problem more quickly. Know what a wrong soil pH looks like versus nematode damage. Also be conscious of pesticide carryover look-a-likes, Prostko says.

“True herbicide carryover doesn’t happen as often as you might think,” he says. “If you follow the label, you will be very unlikely to have a problem with that.”

Eric Prostko, UGA Extension weed specialist, says these weed control programs have worked for him for more than 20 years when starting clean in the field. He has not observed any differences between Prowl- or Sonalan-based programs. Additionally, if you do not like Dual Magnum, substitute Anthem Flex, Outlook, Warrant or Zidua. Substitutes for Cadre are Ultra Blazer or Cobra but lower your weed control expectations, especially if nutsedge and/or sicklepod are present.

The Challenge Of Perennial Weeds

Prostko says in 2023, perennial weeds were a significant problem.

“It’s impossible to control perennial broadleaf weeds in peanuts. We don’t have herbicides that can selectively control those weeds,” he says. “We can spray glyphosate, but we’ll take the peanuts out.

“When we plant peanut in fields where we’ve got dogfennel, horseweed, alligator weed or maypop passionflower, we are going to lose. You cannot kill those broadleaf perennial weeds with herbicides used in peanut,” Prostko says.

“If you are planting peanuts in a field that was pasture the previous year, consider putting something else there. Put Roundup Ready cotton or corn, at least get some Roundup in the system to knock down those perennial weeds, then come back with peanuts.”

Controlling Broadleaf Perennial Weeds

UGA Extension weed specialist Eric Prostko says no peanut herbicides work well on these types of weeds.  Growers who have perennial weeds in their peanut fields might consider the following:

a) If perennial weeds are in small spots and growers are willing to sacrifice the peanuts in those spots, they can be spot treated with a high rate of glyphosate (i.e. Roundup PowerMax3 5.88SL at 44 ounces per acre or equivalent).

b) In the fall after harvest, allow perennial weeds to regrow then treat fields with a high rate of glyphosate. This fall application of glyphosate must be applied at least two weeks before first frost. In the following spring, plant RR-field corn or Xtend soybeans/cotton and plan on using a postemergence combination of glyphosate + dicamba in those crops.

c) It will take multiple years of fall and spring applications of glyphosate to get perennial weeds under control.

d) Avoid planting peanuts in fields with known populations of perennial weeds.

Weather: The Uncontrollable Factor

Hot and dry conditions are usually growers’ biggest concern, Prostko says. Water is needed for herbicide activation, or more accurately, water is needed to move the preemergence herbicide from the top of the soil down into the top two inches or the  zone where weed seed germinate.

“Moisture is also needed to help keep weeds active and growing,” he says. “Why are weeds harder to kill when it is hot and dry? Weeds know what’s going on. When it is dry, the weed leaf cuticle gets thicker, and it’s harder to get the herbicide into the leaf.”

Water can also be the problem at times by washing the herbicide off.

Protect Modes Of Action

One last point Prostko hopes farmers will keep in mind is that they need to be proactive in doing everything possible to protect the current pesticide modes of action because there are no new products in the pipeline.

“It takes 10 years to bring a product to the market,” he says. “I am actually going back and looking at some older products that may have potential in the field because there is no silver bullet coming in the future. That’s why we have got to be timely and do those things necessary to be successful when we do apply herbicides.” PG

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