Common Noxious Weed Overview
Spotted Knapweed
Name: Spotted Knapweed (Centaurea stoebe)
Introduction: From Eurasia as a contaminant of alfalfa and clover seed
Habitat: Any disturbed soil
Infestation: Vacant lots, pastures, rangeland, roadsides, stream banks and landscaping
Available Control: Mechanical, chemical, and biological
Priority of Control: Preventing plant from going to seed, attack in rosette stage
Biological Controls: For more information about these biological control agents of Spotted Knapweed, please visit WSU Extension Integrated Weed Control Project.
For More Detail: Visit the Washington Noxious Weed Control Board listing for Spotted Knapweed.
Canada Thistle
Name: Canada Thistle (Cirsium arvense)
Introduction: Native to southeastern Eurasia, contaminated crop seed
Habitat: Rich, heavy loam, clay loam, and sandy loam, with an optimum soil depth of 20 inches
Infestation: Crops, pasture, rangeland, roadsides, stream banks and landscaping. It can crowd out forage
grasses by up to 60 percent. It can also invade native plant communities.
Available Control: Mechanical, chemical, biological
Priority of Control: Deplete its root reserves before rosette has a chance to over-winter.
Biological controls: For more information about the biological control of Canada Thistle, please visit WSU Extension Integrated Weed Control Project.
For More Detail: Visit the Washington Noxious Weed Control Board listing for Canada Thistle.
Common Bugloss
Name: Common Bugloss (Anchusa officinalis)
Introduction: From Eurasia as a contaminant of alfalfa and clover seed
Infestation: Pastures and rangelands and is a concern to alfalfa production because the succulent leaves and stalks mold the hay once it is baled.
Available control: Chemical, and mechanical
Priority of Control: The most effective control of Common Bugloss is prevention. Above all, prevent plants from going to seed.
Biological Control: There is no known effective biological control for Common Bugloss
For More Detail: Visit the Washington Noxious Weed Control Board listing for Common Bugloss.
Dalmatian Toadflax
Introduction: Native of southeastern Europe and introduced as an ornamental plant because of its snapdragon-like flowers.
Habitat: Coarse, well-drained soils
Infestation: Roadsides and rangelands, in fields, overgrazed pastures, idle cropland and waste areas.
Available control: Mechanical, Chemical, Biological
Priority of Control: Prevent from flowering, keeping foliage down without spreading root fragments
Biological Control: For more information about the biological control of Dalmatian Toadflax, please visit WSU Extension Integrated Weed Control Project.
For More Detail: Visit the Washington Noxious Weed Control Board listing for Dalmatian Toadflax.
Rush Skeletonweed
Name: Rush Skeletonweed (Chondrilla juncea)
Introduction: Central Asia and the Mediterranean Basin including North Africa, Morocco, Turkey, Italy, Spain and Portugal.
Habitat: Well-drained, sandy-textured or rocky soils.
Infestation: Rangelands, semi-arid pastures, croplands, transportation right-of-ways, residential properties and other areas subjected to repeated soil disturbance.
Available control: Mechanical, chemical, and biological.
Priority of Control: Prevent root fragments from producing new plants, prevent from seeding
Biological Control: For more information about the biological control of Rush Skeletonweed, please visit WSU Extension Integrated Weed Control Project.
For More Detail: Visit the Washington Noxious Weed Control Board listing for Rush Skeletonweed.
Hoary Alyssum
Name: Hoary Alyssum (Berteroa incana)
Introduction: European plant in either contaminated lawn seed or hay
Habitat: Adapted to dry soils and can out compete other plants.
Infestation: Waste places, overgrazed pastures, and stressed meadows.
Available control: Mechanical and chemical
Priority of Control: Prevent plant from getting to flower.
Biological Control: There are no insects for biological control of hoary alyssum available at this time.
For More Detail: Visit the Washington Noxious Weed Control Board listing for Hoary Alyssum.