Farm Progress is part of the Informa Markets Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Serving: United States

Killing resistant weeds – reality TV?

One of the most enjoyable parts of my university Extension job is the opportunity to talk with a lot of different people and learn about the real situations occurring in the field on a daily basis.

Some calls are fairly routine and predictable — especially those from my administration wanting to know why I haven’t turned in the past due report or why I was not at the last committee meeting. These are not always as enjoyable, but come with the territory until I learn to mend my ways.

The county agent, consultant, and farmer calls are much more enjoyable, always interesting and occasionally easy enough for me to answer. They usually vary by the season and by the environment. If it is dry, we want to know how to kill weeds that are stressed and not growing. If it is raining and wet, we want to know how to kill weeds that are too big and rank. Even if there are some similarities, each situation is unique and requires some solution tweaking.

We may be missing a great opportunity by not capturing this in a reality show. Everyone else seems to have a reality show, why can’t agriculture? I can see it now. A call comes in to Extension Central that pigweeds have escaped. Everyone goes into emergency mode — Code Red, Code Red. The film crew and Extension personnel rush to the field to find weeds waving in the wind, pollinating and setting seed.

The narration, with dramatic background music, explains how these things proliferate and consume the land. Farmer and specialist staff retreat to the office, where the air conditioner is broken, and discuss the available options. Additional forces are needed and equipment dealers and chemical industry representatives are called in.

In the meantime field shots show close ups of weeds with narration. “The weeds are consuming the land and sending pollen out to points unknown as we speak! We must do something fast!”

We could throw in a rain shower, an equipment breakdown, or an employee having to be bailed out of jail to add drama and more reality.

Finally, a plan is devised — it is unique and has a chance of failure under these adverse conditions, but is our best shot. With farmer perspiring and sprayer operator tense, the herbicide is applied, and a time lapse camera captures some weeds dying rapidly. Others, however, respond slower.

Finally, most are dead, and the plan is followed up by hand-hoeing to insure there are no survivors. The narrator comments that the beasts could escape again at any time.

The film company pays the farmer big dollars for the series; thus a profit is finally realized from that field. Agriculture becomes a household word and everybody is a winner.

Now that everyone has had a chuckle — you probably needed that, let’s get back to real reality and discuss some real questions.

What about using a ropewick applicator for control of pigweed over cotton and soybean?

We are all aware that ropewicks were designed to apply glyphosate over crops prior to Roundup Ready technology. But, we have tested other herbicides through ropewicks with varying levels of success on different weeds.

Unfortunately, our level of success on pigweed has been low. Ignite and Gramoxone are not translocated and simply burn some of the top growth on the side of the weed wiped. Wiping two ways just burns it on both sides, but does nothing to the lower parts of the weed that simply continues to grow.

We have trouble killing a 6-inch pigweed with Flexstar when it is sprayed with good coverage, so it stands to reason that wiping just the top portion of a big weed will be ineffective. The most injury (note I did not say control) to pigweed will likely come from 2,4-DB in soybeans. This herbicide is translocated, but big pigweeds can tolerate a lot of 2,4-DB. Ask any rice farmer who has attempted to control big weeds on levees.

It should go without saying, this is not an option over cotton. The herbicide must be labeled in the crop for it to be a legal application. 2,4-DB works in the plant by breaking down into 2,4-D. Probably no more discussion is needed about cotton. The pigweeds wiped over soybeans will curl, twist, and set fewer seed, but likely will not die.

Some have asked about adding surfactants to the solution. This may be good if you are using an applicator that sprays the solution on a carpet roller, but if it is a true ropewick applicator, the surfactant will slow the wicking speed of the herbicide solution. We have used surfactant to slow the dripping from the ropes in applicators we felt were allowing too much herbicide to drip onto the crop.

Is this a resistant weed?

Every weed that survives in a field is not resistant, but if you have done a good job of applying herbicides, and it did not die, there is reason for suspicion. I get several calls each year indicating the weeds that have been sprayed with excessive high rates an excessive number of times must be resistant. They may be, but sometimes when we get behind in weed control, it is very difficult to catch up.

If you think a weed is resistant, we are interested. We have a very active resistant screening program at the university. Weed scientist Jason Norsworthy at Fayetteville, Ark., gives leadership to this program, but weed scientists Bob Scott and I also screen biotypes that are suspected of being resistant to field herbicides.

If a biotype that has been previously controlled suddenly escapes, a call to the county agent is usually all that is needed to get the plants into our screening program. The standard procedure is to collect suspected plants from the field, transfer them to the greenhouse and allow them to set seed.

The seed are collected and planted and seedlings are sprayed with suspected herbicides. This is good information also in that it can be an indication that something went wrong in the herbicide application. Maybe a check of application techniques is in order.

What can I use in a spot sprayer?

Some farmers have resorted to spot-spraying instead of hand-hoeing to manage scattered escapes in the field. Again, the herbicide used must be labeled in the crop. Ignite will probably be the herbicide of choice in most spot-spraying situations.

Although Ignite is not labeled for use in non-LibertyLink crops, it does have a tolerance in cotton, soybean and corn and can legally be used as long as the rates do not exceed those on the label. This is usually not a problem due to the small amount of area being treated by spot-spraying.

Mixing Ignite at a 2 percent solution and wetting the weed has been very successful. Nozzles that emit more of a stream than a big cone or fan can be directed at the weed without taking out big spots of crop around the weed.

There are several experiment station and county field days scheduled over the next several weeks. Let me encourage everyone to attend these events and learn what is new as well as ask questions and discuss issues that will make a positive difference on your farm.


TAGS: Soybeans
Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.