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

Arkansas weed control Don't ignore plant-back restrictions

As I write, our place is saturated and we are dodging tornadoes again. Farmers are very frustrated because they would like to be through planting corn and rice, and have a lot of soybeans planted.

However, many have nothing planted and some do not even know when the water will go down.

This too shall pass, but we sure need it to hurry up.

I get some questions about burn down, but nothing compared to what my university counterparts get. The burn down situation in general is the source of frustration because a lot of farmers have not been able to get that done either.

Now a herbicide such as 2,4-D, or dicamba is really needed in the burn down, but the crop needs to be planted as soon as it is dry enough.

While it is frustrating and you would like to wish away plant-back restrictions, you can not let being behind force you into a mistake that you have to live with all season.

The University of Arkansas weed scientists put a plant-back interval table in the MP 44 (Arkansas Extension publication). Some of these restrictions are label restrictions and some are rules of thumb on the amount of risk they are willing to take on herbicides such as 2,4-D and dicamba where labels are often vague.

I get questions all the time as to whether the plant-back interval on certain herbicides is real or if it is just a “label thing?” I also get questions on how long do I really have to wait?

If the herbicide has a plant-back interval, it usually is because it can injure the crop.

Some farmers make the mistake thinking that because you can use 2,4-D on rice, it will not hurt the crop anytime. A burn-down application of 2,4-D can hammer rice if the herbicide has had not had time to degrade prior to germination.

Most herbicides are broken down by microbial degradation. Microbes work faster in higher temperatures and ideal soil moisture. A good, safe rule of thumb on 2,4-D is 21 days. A lot of time you will be safe at 14 days, but it is hard to outguess the microbes.

Don't box yourself in on what you can plant or when you can plant by choosing the wrong burn-down herbicide this time of year.

I am not going to attempt to go into a lot of burn-down options. I can't keep up with all of them — the companies combine ingredients, re-package and change the names too fast for me. However, there are some options that can help with short plant-back intervals.

Aim can provide some “heat 'em up” in some situations with no plant-back restrictions.

In soybeans, Valor can add heat plus residual with no plant-back restrictions (Valor has a 30 day plant-back in other crops).

In soybeans and cotton you must kill emerged marestail. Dicamba and 2,4-D work best, but if you can not wait on the interval, you need a disk. Also, the 2,4-D restrictions kicked in April 15.

Gramoxone will not control marestail, and most of the ALS inhibitor herbicide additives such as Harmony, Synchrony, Envoke or First Shot provide only postemergence suppression.

The Ignite label continues to be expanded and the price has become much more competitive. It is a hot herbicide that is an effective burn-down option when the weather is warm and sunny — even on marestail. There is no plant-back restriction on corn, cotton or soybeans. Thorough spray coverage with Ignite is critical.

In rice, First Shot can be added to glyphosate with no plant-back restriction, and it is excellent on smartweed and some of the other broadleaf weeds.

There is now a 24-C preplant label for Permit in rice. It can help a lot in situations where there is a lot of emerged nutsedge and also can help some on smartweeds. In addition, Permit can have residual activity on some rice weeds at the higher use rates.

Hopefully, when you read this, all of the weeds have been burned down, the weather is warm and sunny, everyone is in the field and you are wondering “what rock has he been under!”

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.