Delaware

University of Delaware Weed Science: http://extension.udel.edu/ag/weed-science/

 

Herbicide Resistant Weeds in Delaware

Updated: September 22, 2016. Mark VanGessel, University of Delaware; www.weedscience.org – Delaware

Reading this list: Each weed with herbicide resistant populations in this state is listed. Underneath each species is a list of the unique resistant biotypes of that weed in the state, according to the herbicide group(s) they are resistant to.

Note: Equipment is a primary vector for the introduction of resistant weeds into Delaware and for spread within the state.

First priority: Horseweed. Highly prevalent. Blew in from Ohio Valley thru TN & KY, to DE within 1 year. Also a problem in veggie crops.

  • Group 9 (glyphosate)
  • Group 2
  • Group 2 (ALS) + Group 9 (glyphosate)
  • Group 22 (Paraquat)

Second priority: Palmer Amaranth

  • Group 2 (ALS)
  • Group 9 (glyphosate)
  • Group 2 + Group 9

Third priority: Smooth/redroot pigweed

  • Group 5 (atrazine)
  • Group 2 (ALS)

Lambsquarters

  • Group 5

Common chickweed – problem in small grains

  • Group 2 (ALS)

Italian ryegrass

  • Group 2 (ALS)

Common ragweed

  • Group 2 (ALS) + Group 14 (PPO)