recently found in goshen county

Palmer Amaranth

​Palmer has been found in Goshen county and proper identification is critical. Typically found in crop systems, palmer amaranth is a highly invasive species. Once palmer is established it only takes a few years for the plant to reduce crop yields by 90% in certain situations. It is known to quickly develop resistance to several herbicides.​ This weed has put farmers out of business in the United States and is now a threat to Goshen county.
​If seen, please contact GCWP, UW Extension or your crop adviser.

identification 

  • Looks similar to redroot pigweed
  • Long, slender seed head up to 2 feet tall
  • Smooth, hairless stem
  • Symmetrical (poinsettia-like) leaf arrangement
  • Mature plants have petioles longer than the leaf blade
  • Prolific seed producer, 250,00 - 500,000 seeds per plant
For more information on Palmer amaranth and management options.
​
Linked articles credited to Daniel Tekiela, Gustavo Sbatella, University of Wyoming and Nevin Lawrence, University of Nebraska-Lincoln.

MANAGEMENT options

  • Chemical Control 
    • Dry bean, Reflex (post-applied) herbicide is an effective control option.
    • Corn, Dicamba (Clarity, DiFlexx) applied on corn has shown sufficient results. Pre-emergent herbicide will be critical due to season-long germination potential. 
    • Sugarbeets, ​​​herbicide application of Outlook, Sequence, or Dual can prevent emergence. Rotational crop strategies is the best option to control palmer amaranth in sugarbeet fields. 
  • Mechanical 
    • Mowing is not an effective practice to reduce seed production. Tillage can be a effective if seeds are buried 2-3 inches deep. 
    • Manually hand pulling, bagging, and disposing of the plant is an effective control method. 
  • Cultural Methods 
    • Rotation of crops allows for varied tillage, herbicide options, harvest timing, etc. Several aspects need to be considered when dealing with herbicide-resistant and aggressive weeds, such as palmer amaranth. 

Watch list

These weeds may not be in Goshen County...yet! Be on the lookout for these as once they show up it will be very difficult to get rid of them.
Ventenata
Similar to medusahead, ventenata is an annual grass weed which is highly invasive. It is currently found in three northern counties of Wyoming. It may appear very similar to downy brome (cheatgrass) except awns are bent at a 90 degree angle, similar to wild oat.
Medusahead
Found mostly in the Pacific Northwest, this annual weed is only in the northern part of Wyoming currently. Medusahead is extremely competitive; it can even overtake rangeland infested with downy brome (cheatgrass). Often confused with foxtail barley, it can be distinguished by its mature head. Awns or beards are typically twisted.
Photos courtesy of: Weeds of the West