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Controlling Weeds in Sunflower Circa 1967

Thursday, January 3, 2019
filed under: Weeds

       Sunflowers are often a weedy crop.  They compete well with weeds but do not develop ground cover quickly enough to prevent weeds from establishing.  Since weeds frequently emerge before sunflowers, many can be killed by spike tooth harrowing about 1 week after planting but before sunflowers germinate. After the sunflowers emerge, such implements as the weeder, rotary hoe, spike tooth harrow, or coil spring harrow may be used to kill weeds.
       Sunflower seedlings are strongly rooted, so small emerging weeds in the ‘white’ stage can be uprooted and killed without injury to the larger sunflowers.  Setting of the harrow or weighting of the rotary hoe to do the most damage to the weeds and the least to sunflowers can be accomplished on a ‘try and adjust’ basis.  It may pay to harrow the field several times if weed emergence warrants it.
       Row crop cultivation to kill weeds between the rows is the major method of weed control.  Cultivation should be done carefully, as sunflowers can be easily damaged or broken. Tests with flame cultivation for 3 years at Crookston indicated that effective weed control in the row by flaming resulted in lower sunflower yields.  Flaming is expensive and does not save cultivation expense because the area between the rows is cultivated at the time of flaming and the number of cultivations often is increased.  Furthermore, weeds afford considerable competition to the crop before flaming can be done.
       EPTC?(Eptam 6-E) at 3 pounds per acre applied before planting and incorporated into the soil has given excellent control of many grass and broad-leaved annual weeds.  However, disking or other incorporation must be accomplished within minutes after spraying to avoid loss of the herbicide.  Spraying the plowed ground followed immediately by seedbed preparation of cross disking twice at right angles, spike tooth harrowing once, and planting has given good weed control and no sunflower injury.  EPTC has not been effective on wild mustard or smartweed and only occasionally effective on wild oats.
       EPTC?often is applied broadcast from a boom mounted on the front of a disk.  For band application, rotary tiller or disk attachments in front of the planter and behind the spray nozzle are used to incorporate EPTC 3 inches deep.
         Sunflowers are tolerant to certain other effective preplanting, pre-emergence and postemergence herbicides that do not have label approval from the USDA Pesticides Regulation Division.   
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