Rating burndown studies this morning, I could not help but notice that the horseweed (marestail) had grown about 3 inches since last Friday. 

Some is already 6 inches tall.

It will quickly get large enough to make even some of our better burndown options inconsistent. Judging by the calls today, others have noticed this too and realize that our burndown options are more limited with cotton planting time just a couple weeks off.

Of course, Liberty in past years has been an option to control horseweed where cotton was to be planted quickly. 

However, with the concern about supply of this herbicide, along with the lack of a rebate when used as a burndown, this one is not a real good option this year.

Depending upon expected planting date, we are running out of time to go with our main “go to” dicamba-based burndown program.

However, one must look at the label of the different dicamba products sold as there are some differences.

The most notable is that Clarity has a supplemental label that allows cotton to be planted after 15 days and one inch of rainfall once Clarity is applied.

Remember, in order to utilize Clarity in this fashion you must have a copy of the supplemental label in hand. 

All the generic formulations of dicamba (Banvel, Rifle, Agri Star, etc), and Clarity if you do not have the supplemental label, must have a waiting period of 21 days and one inch of rainfall before cotton can be planted.

Below are more thoughts on late horseweed burndown in cotton:

Dicamba 8 oz/A + glyphosate 22 oz/A

Management Considerations

1.        Clarity rates of 8 oz/A can be applied up to 21 days before planting and 1” of rainfall to avoid crop injury.

2.        Generic dicamba products at rates of 8 oz/A can be applied up to 21 days before planting and 1” of rainfall to avoid crop injury.

3.        Remember to use a surfactant (0.25% NIS) with dicamba applied alone or with a glyphosate product that has no or moderate surfactant load.

4.        Be cautious of making overlaps!!

Gramoxone Inteon 40 to 48 oz/A + 0.25% NIS + Caparol 32 oz/A or Cotoran 32 oz/A or Direx 16 oz/A

Management Considerations

1.        This application can be applied right up to planting.

2.        Gramoxone Inteon rates below 40 oz/A will not provide as consistent control of horseweed as higher rates.

3.        For larger horseweed (>6”) use 48 oz/A of Gramoxone Inteon.

 Liberty 29 oz/A + Caparol 32 oz/A or Cotoran 32 oz/A or Direx 16 oz/A

 Management Considerations

1.        This would be a last resort option due to cost and Liberty supply concerns.

2.        This application can be applied right up to planting.

3.        Liberty will not provide good control of horseweed under cool conditions.

4.        Liberty performance is very temperature dependent. It works best with highs in the 80s and lows in the 60s.