WEEDS & CRP

  [update 7/21/14]:-- It's most unfortunate that I did not scout our fields last fall.  Some of our CRP fields have significant amount of Delmation Toadflax that did not get treated until this summer.  Last year we had a young man scout and treat these fields, but there was too much for him to treat using Husky and Tordon.  There is too much to treat with any aggressive chemistry now.   It would limit our crop selection for the fall of 2015 or spring of 2016.  I have just treated these fields with Range Star (2-4D + Banvel) and two surfactants (WetCit + M90).  I'll update later on the effectiveness of this treatment and whether WetCit cut through the wax.
      This spring we put spring barley as the first crop on a CRP field.  All of the grasses were dead, but the field has a heavy infestation of Rush Skeleton Weed.  We have treated this aggressively with applications of Rt and 2-4D.  Timing is everything with this weed.  We have successfully put the hurt on it while in the rosette stage, but little happens once it bolts.  We'll harvest this crop within three weeks.  I'm thinking that we may want to mow this field soon following harvest to stop any new seed development.  Rush S. is one that you do not want to do any type of cultivation on as that drags roots and promotes new starts.  Tours that I have been on clearly showed where new patches sprang up from the weeder dragging roots.  Most perennials have that potential; however, Rush S. takes full advantage of roots being dragged across the field. 
 Recently I had the good fortune of being asked by a family wishing to put CRP ground back into production, to express my thoughts and interest.  Since we will be taking significant acreage out of CRP ourselves in a couple of years, this was an opportunity to give thought to what is currently growing in the field, and how we should proceed for a cropping scenario.  We have two years to prepare.  This family had 1-4 months to prepare.  If, when evaluating a field, you find a difficult weed scenario, the more time you have to address the problem the better.
     In this families case, the field generally had a good stand and mixture of grasses that presented no difficulty to remove.  The weed spectrum included the usual annual broadleaves and grassy weeds along with a significant amount of Canadian Thistle.  These don't create any particular difficulty when going into a cash crop.  There is adequate chemistry available for successful Direct Seeding that will give good control before planting, as well as in-crop control.  The trick is to chose chemistry that does not limit your choice of cultivar for your cash crop.   In this families case, what was disappointing was to find a high infestation of Delmation Toadflax .  My guestimate is that 80% of the field is contaminated.  There are a number of densely populated patches, and single plant scatter throughout the remainder.  I spent a lot of time talking to people, looking up reports, and surfing the web for success stories on controling this noxious weed.  There was no quick and easy formula that I could find.  Whether you chemical'd or cultivated the field, it was going to have to done with persistence and with repeated operations for a lengthy period of time.  When established, the Toadflax plant has an extensive root system.  It is a prolific seed producer, and the seed will remain viable in the soil for 10 years.  (This tells me not to plant this seed through soil disturbance.  Leave it on the surface where weather and critters can attack it.)  The leaf structure includes a thick waxy coating that is difficult to penetrate with chemistry. (This tells me that a contact chemical will need a very good surfactant and probably used at a higher than normal rate.)
      When I synthesize all this material down for a management plan, I conclude that Delmation Toadflax  is no different than any other noxious perennial weed.  You have to stop the seed development and deplete the root reserves to remove the problem.  Timing is critical to reach your goal for the particular type of chemistry you are using.  Research supports the best timing for impacting the root system is in the fall with a systemic chemistry.  Antidotal statements indicate that most of the common chemistry we use for weed control in our crops will have an impact on Delmation Toadflax seed development when timed properly.  Severe damage to the seed stalk at the start of bloom either mechanically or chemically will stop seed production and help draw down root reserves as it attempts to recover.  Any management plan to remove this noxious weed from the field will include years of hand roguing your cash crop.
       I don't consider cultivation as an option.  It makes no sense to me to destroy all the gains in soil health made over the years in CRP, --- as well as put 10-25 years of seed in a "soil" bank, and make annual withdrawals for the next 10 years.  The seed will degrade much faster on the soil surface through weather and fauna.