Winter Annual Weed Control  04/03/18 3:42:18 PM


Winter Annual Weed Pressure
Taken 4/3/18—Cass Co. NE.
Wiles Bros_2X3 small signs
Scouting your fields???  It is hard to believe that any field can turn this green with weeds when the soil temperature is only 34.  Winter Annual Weeds thrive in this weather.  Above, we have most every winter annual broadleaf weed common in our area.  Henbit, Marestail, Tansy Mustard, Shepardspurse and Field Pennycress are all lying in wait, ready to actively grow (bolt out of the rosette stage of growth) to form the flowers, fruiting bodies and seeds for next year.  NOW IS THE TIME---to formulate you plan of attack for controlling winter annuals weeds.  There are a whole host of herbicide combinations that work on controlling this problem. 
 
TIMING IS EVERYTHING—Ideal herbicide applications are made prior to the “bolt” stage of development and when the air temperatures are 40 degrees or more.  We need warmer temperatures to increase metabolism and get the weeds actively growing in order to achieve better control with the herbicide being used.  BUT, you have to get it applied before these weeds flower in order to gain measurable success.   When burn down applications are made, many people will be concerned with the effectiveness of burn down herbicides when it is cold after application.   Wide temperature swings in the air and soil lead to this conversation when the application was made maybe 10 days ago when it was 60 and it hasn’t been much above 40 degrees since then. The net result is the same, the weeds die — it may just take a little longer. At this stage of the game and given the plant size that many of these weeds have already achieved this spring, treatments should be a consideration as soon as the soil is dry enough for an application to occur
Some key things to keep in mind concerning early burndowns:
  1. avoid applying to frost-covered weeds
  2. include dry AMS (17 lbs/100 gal spray)
  3. avoid mixing with high rates of contact herbicides
  4. wait until daytime temps are 40F, or higher
  5. make the application when the weeds are small, in the rosette stage, and prior to vegetative bolting (stem elongation)
  6. IF weeds have bolted (Stem elongation—have gotten BIG) a tillage pass is a viable treatment option as even the best herbicide tank-mixes will have control challenges on large winter annual weeds.
     
    Most winter annuals over-winter in a dormant rosette stage and when the soil has warmed into the high 30's/low 40's in the spring they will green-up, bolt (grow a stem out of the rosette) and flower/reproduce prior the heat of the summer months.  The soil temperature has been consistently in the 40’s for a number of weeks now which has encouraged active weed growth.  To control these weeds in No-Till acres, the use of 2,4-D or Banvel in a pre-plant burn down application in combination with a Roundup WeatherMax tank mix is a consistent treatment choice.  This application has been widely used in No-Till Soybean applications for years.  It can also be used in corn.  This is normally combined with a Acetochlor/Atrazine combination which is again a bit of a standard of pre-plant corn herbicide choices. 
    The 2,4-D/Banvel component, if used in a burndown treatment on corn applications right before planting, can increase chances for seedling injury (plants emerged twisted, onion leafing, buggy whipping). This is NOT the norm. and usually only happens when corn is slow growing during cool and wet periods prior to soil emergence--typical of conditions with earlier planted corn.
     
     
    John W. McNamara
    Agronomist
    Wiles Bros. Inc.
    606 Wiles Road
    Plattsmouth NE. 68048
    (402) 298-8550--Office
    (402) 499-3870--Cell
    (402) 298-7174--Fax
 
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