Brake F2 Section 18 Emergency Exemption For Cotton

Written by Keith Edmisten

From Dr. Alan York, Crop Science

Last week, North Carolina and three other states (GA, SC, TN) were granted a Section 18 Emergency Exemption for use of Brake F2 herbicide on cotton.  A label and an MSDS sheet are linked below.  This product can only be used in those counties specifically designated on the label (shown toward end of the label).  Most cotton-producing counties in NC are covered; note that Camden, Carteret, Iredell, and Warren are not on the list but there is very little cotton in those counties.  We can treat up to 45,000 acres in North Carolina.

Brake F2 contains two active ingredients and is formulated as a 2.6 lb ai/gal product.  It contains 1.6 lb ai/gal of fluridone and 1.0 lb/gal of fomesafen.  Some of you may be familiar with fluridone as the active ingredient in the aquatic herbicide Sonar.  Fomesafen is the active ingredient in Reflex.

This Section 18 is specifically for control of glyphosate-resistant Palmer amaranth.  A Section 18 exemption is typically based upon a pest causing significant financial losses and for which there is no currently registered product that adequately controls it.  That is not the case with Palmer amaranth; although it has been expensive, we have been able to control Palmer with currently registered herbicides.  This particular Section 18 was justified on the basis of resistance management.  Fluridone is a PDS inhibitor (inhibits carotenoid biosynthesis at the phytoene desaturase step; Group 12 mode of action; it is a bleacher but not the same mode of action as Command).  Some of you more seasoned individuals will remember Zorial, which was also a Group 12 herbicide.  In cotton (and most other crops), we are relying on a limited number of modes of action.  There is currently no other Group 12 herbicide being used on agronomic or horticultural crops except apples, peaches, and pecans.  Hence, Brake F2 brings us a “new” mode of action.

Brake F2 would be applied at 1 pt/acre on most of our soils; the label does allow 1.5 pt on medium- and fine-textured soils.  At 1 pt/acre, Brake F2 gives 0.2 lb ai/acre of fluridone and 0.125 lb ai/acre of fomesafen.  That amount of fomesafen is equivalent to 0.5 pt/acre of Reflex, or one-half the typical rate.

Our research on Brake F2 has been limited to a few trials in 2013.  Based upon that, it appears that the following statements can be made:

1. There is good cotton tolerance to Brake F2.  Cotton is extremely tolerant of fluridone.  If there is injury from Brake F2, it would come from the fomesafen.  However, there should be minimal injury from that half rate of fomesafen.
2. Palmer amaranth control is good.  It is hard to say control is better than what we can achieve with standards such as Warrant plus Reflex or Reflex plus Direx, but certainly control is good.
3. Brake F2 may last a little longer than our current standards.  Nevertheless, appropriate postemergence applications will be needed (basically those we have recommended in recent years).

The following are pertinent points from the label:

1. Use Brake F2 only for control of Palmer amaranth populations with resistance to glyphosate.
2. Brake F2 can be applied preplant surface or preemergence.  If applied preemergence, make sure it goes on before the cotton cracks the ground.  If preplant, it can go on up to 14 days ahead of planting.  After preplant application, do not till.  We have no experience with Brake F2 applied preplant followed by strip-tilling, but one would expect the strip-tilling would compromise control in the tilled area.
3. If the cotton stand is lost, one can replant only to cotton.  Do not apply additional Brake F2 with the second planting.
4. Start clean.  Control emerged weeds with either tillage or an appropriate burndown application.
5. Do not use for more than two consecutive years.
6. Fields treated with Brake F2 must be tilled prior to planting rotational crops other than cotton.
7. Rotational restrictions, for a 1-pt/acre application rate:  0 months for cotton; 4 months for soybean and small grains; 6 months for corn and peanuts; 18 months for other crops.

Source:ncsu.edu