California

University of California Weed Research and Information Center: http://wric.ucdavis.edu/

University of California Weed Science: http://ucanr.edu/blogs/ucdweedscience/

Herbicide resistant weed challenges in California

Herbicide resistant weeds in rice are a high concern in California, including bulrush, watergrasses, and smallflower umbrella sedge.

Terrestrial resistant weeds of high concern include hairy fleabane, ryegrass, horseweed, and junglerice, based on acreage affected and difficulty of control.

Herbicide resistant weeds in California

Updated November, 2016. Source: Brad Hanson, University of California; www.weedscience.org – California

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.

 

Ricefield bulrush

  • Group 2
  • Group 7

Early watergrass

  • Group 8

Late watergrass

  • Group 1
  • Group 8
  • Group 1 + 8

Smallflower umbrella sedge

  • Group 2
  • Group 7

Horseweed

  • Group 9
  • Group 9 + 22

Hairy fleabane

  • Group 9
  • Group 9 + 22

Junglerice

  • Group 9

Italian ryegrass

  • Group 9
  • Group 10

Perennial ryegrass

  • Group 2

Rigid ryegrass

  • Group 9

Common groundsel

  • Group 5

California arrowhead

  • Group 2

Russian thistle

  • Group 2

Wild oat

  • Group 8

Eared redstem

  • Group 2

Redstem

  • Group 2

Barnyardgrass

  • Group 1 + 8

Little seed canary grass

  • Group 1

Smooth crabgrass

  • Group 4

Annual bluegrass

  • Group 9

Palmer amaranth

  • Group 9