Class B and C Reduction Weeds:

Weeds listed in this category are too widespread to be immediately controlled or eradicated Countywide. Currently Diffuse Knapweed is classified as a reduction species in Okanogan County. Landowners with one or more of these species present on their property should concentrate their initial reduction efforts in high-priority areas such as roadways, driveways and property boundaries.

• Diffuse Knapweed (Centaurea Diffusa)
• Spotted Knapweed (Centaurea Maculosa)
• Russian Knapweed (Centaurea repens)
• Perennial Sowthistle (Sonchus Arvensis)
• Houndstongue (Cunoglossum Officinale)
• St. Johnswort  (Hypericum Perforatum)
• Longspine Sandbur (Cenchrus Longispinus)
• Yellow Toadflax (Linaria Vulgaris)
• Sulfur Cinquefoil (Potentilla Recta)
• White Top/Hoary Cress  (Brassicaceae)

· (Centaurea Diffusa)  Diffuse Knapweed, biennial

· ( Centaurea maculosa)  Spotted Knapweed, biennial, perennial

· ( Centaurea repens L.)  Russian Knapweed, perennial

DIFFUSE KNAPWEED PHOTO is a biennial. The first stage of the plant is a rosette. The rosette has lobed leaves, the stem leaves are smaller, simpler and do not have a flower head. The second stage of the plant grows 1 to 3 feet tall. It has a single upright stem has numerous spreading branches that end in pale yellowish-green spiny bracts. These bracts are around the numerous, ¼ inch in diameter flowers. The flowers are usually white in color but occasionally they are pink or purple. The seeds are oblong, hairy, brown to black in color and are about 3 millimeters long. It has a stout taproot, and spreads primarily by seed. Diffuse is very bitter to the taste.

SPOTTED KNAPWEED PHOTO is a biennial or a short-lived perennial (3-5 years). The first stage of the plant is a rosette. This rosette has lobed leaves, the stem leaves are smaller, simpler and do not have a flower head. The second stage of the plant may become multi-branched from lateral root buds. It grows 1 to 3 feet tall, is branching and hairy. Flowers are ¾ of an inch in diameter. The flowers are purple to pink in color and are located on the tips of the branches. The bracts have dark tips on them that make them appear spotted. It has a stout taproot and spreads primarily by seed. Spotted is very bitter to the taste.

RUSSIAN KNAPWEED PHOTO is a perennial that starts out as a rosette. The leaves of a rosette are oblong or tapering to both ends, covered in hair, bluish-green in color. The second stage of the plant grows 1 to 3 feet tall. The stems are upright and branched. The amount of branching is determined by the spacing of other plants, the smaller the spacing the less branching. At the end of each branch there is a solitary head. Bracts that surround the base of the head have a few woolly hairs or are hairless; greenish-yellow in color, about ½ of an inch long. The flowers are about ¾ of an inch in diameter, numerous, and lavender-blue to pink in color. Russian has a deep, dark brown to black, heavily scaled lateral roots. It reproduces by both seed and root. Localized spread is primarily by lateral root extension.

Environment: Spotted and Diffuse knapweed readily colonize different soils over a broad range of environmental conditions. They are not common weeds on cultivated land or irrigated pasture. They prefer open sites in the sun. Diffuse and spotted knapweed prefers upper elevation grasslands and timber sites. Russian knapweed is common on heavier, often saline soils of bottomlands. It is highly competitive on sub irrigated slopes and flats. It may grow in hayfields, pastures, grain fields and irrigation ditches.

Rate of Spread: There is some evidence that knapweeds release chemical substances, which inhibit surrounding vegetation. This enables the plants to invade rangeland, waste areas, pastures, and roadsides very rapidly.

1. Manual control by hand pulling can be effective only if the program is very rigorous (pulling 2-3 times a growing season) and is used along with another form of control (cultivation, herbicides, or biological)
2. Chemical control is extremely effective if the herbicides is applied at the correctly. Early spring application eliminates both the spring and fall seedlings. Russian knapweed takes a higher rate and needs to be sprayed during the flowering stage of the plant, because is spreads by root.
3. Cultural method can help control knapweeds. Planting of competitive perennial grasses, a management of rangelands to avoid disturbance and excessive use. Mowing and burning plants are not recommended control methods because they seldom stop seed scatter.
4. Biological control is limited to its success. Selected insects reduce the amount of weed seed produced in some situations but they do not eliminate the seed source. Subanguina picridis a nematode (Russian).

Herbicide Control: This per acre cost depends entirely on many variables, example: backpack, ATV, truck boom, or helicopter applications. Each method has a different cost rate per acre, also depending on the type of Herbicide selected, the size of the infestation and the price paid per gallon of selected Herbicide. We can give close estimates based upon the 2002 bid price cost for ground application.

Affects on Water Quality: Knapweeds increase adverse affects on fish and wildlife by water runoff and soil erosion on stream banks and sediment in lakes and rivers. Habitats and food sources are affected and greatly changed in their ecosystems. Stream flows can also altered and this affects all systems of water quality.

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Biology of Plant: A perennial. Plants are usually 2 to 4 feet tall, succulent, and exude a milky juice when injured. Leaves have a clasping base and mildly prickly margins which vary from deeply toothed to nearly entire. Upper leaves are fewer and much smaller than the basal ones. The flower head is 1 to 2 inches wide, and rich yellow in color. Numerous gland-tipped hairs on involucre bracts and flower stalks help distinguish this species. Seeds are dark brown, prominently ridged and wrinkled, with a tuft of soft white pappus bristles.

Environment: It is common in gardens, cultivated crops, ditch banks, and fertile waste areas where adequate water is available.

Rate of spread: Spreads by seeds. New shoots emerge from stout lateral roots. Wide spread throughout North America.

1. Chemical control is better when combined with other control methods because the species is relatively resistant to many common broadleaf herbicides.

2. Cultural control Tillage can reduce perennial sowthistle stands. Mowing would not be as effective as tillage. Tillage at the seven to nine leaf rosette stage seems to work best for reducing the reproductive capacity of the roots.

3. Biological control Sheep and cattle can be an effective control method. No insect biocontrol agents are presently available in Washington.

Herbicide Control: This per acre cost depends entirely on many variables, example: backpack, ATV, truck boom, or helicopter applications. Each method has a different cost rate per acre, also depending on the type of Herbicide selected, the size of the infestation and the price paid per gallon of selected Herbicide. We can give close estimates based upon the 2002 bid price cost for ground application.

Affects on Water Quality: Perennial Sowthistle likes to grow along rivers and lakeshore areas.

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Biology of Plant: Biennial to short-lived perennial. Forms a rosette it’s first year and then bolts in it’s second year to a plant 1 to 3 feet tall. The plant produces more than 600 seeds per plant.

Soil Types: It grows in various types of soil, preferring coarse and sandy soils.

Environment: It is found in pastures, roadsides, meadows, and forests. It prefers moist areas and is extremely shade tolerant.

Rate of Spread: This weed can spread rapidly due to Velcro-like burred seeds. They cling easily to passing animals and clothing.

Rec./Control Methods:

1. Manual control digging with a shovel and hand pulling is effective if done before the plant is in full bloom.

2. Chemical control has proven very effective if done correctly. Spraying should be done while the plant is still actively growing for the most cost effective use of herbicides.

3. Cultural controls None known, but any type of planting or vegetation is recommended.

4. Biological controls none known at this time. Testing is continuing in Canada.

Herbicide Control, Estimated Cost per Acre: This per acre cost depends entirely on many variables, example: backpack, ATV, truck boom, or helicopter applications. Each method has a different cost rate per acre, also depending on the type of Herbicide selected, the size of the infestation and the price paid per gallon of selected Herbicide. We can give close estimates based upon the 2002 bid price cost for ground application

Affects on Water Quality: Same as all other Noxious weeds invading sites and affecting the habitat and wildlife areas

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Biology of Plant: It is a perennial. The stems are upright, reddish, woody and grow 2 to 3 feet tall. Leaves are numerous, simple, opposite, and when they are held up to the light each leaf appears to be perforated by pinpricks. The flowers have numerous stamen and five yellowish-orange petals. When livestock eat this plant it causes photosensitizing reaction to non-pigmented skin. It reproduces by both seeds and rhizomes from the roots.

Soil Types: Found in various heavy soils, seeming to like sandy, gravely soils the best.

Environments: It invades pastures, non-crop areas, and grazeable woodlands.

Rate of Spread: Seeds have a gelatinous coating that sticks them to legs, hooves, boots, vehicles and other objects enabling it to spread rapidly. Spreads underground and above ground creeping stems.

Rec./Control Methods:

1. Manual control is not recommended due to the plants reproduction, but repeated cultivation soon destroys this weed: therefore, it is not found in cultivated crops. Rotation of pastures or perennial plantings to cultivated crops for 1 or 2 years reduces problems. Mowing several times to prevent seed maturation helps control spread of the plant.

2. Chemical control is effective if applied properly. Cultural controls can control this plant. Rotation of pastures or perennial plantings to cultivated crops for 2 years reduces the seed source. Mowing several times helps control spread of the plant.

3. Biological control can help control this plant but in northeastern Washington, the beetles control is less effective because climate limits their populations. The beetles introduced include; Chrysolina quadrigemina, Chrysolina hyperici, Agrilus hyperici, Zeuxidiplosis giardi, and Aplocera plagiata.

Herbicide Control, Estimated Cost per Acre: This per acre cost depends entirely on many variables, example: backpack, ATV, truck boom, or helicopter applications. Each method has a different cost rate per acre, also depending on the type of Herbicide selected, the size of the infestation and the price paid per gallon of selected Herbicide. We can give close estimates based upon the 2002 bid price cost for ground application.

Affects on Water Quality: St. Johnswort has not typically grown along lakes or rivers, but will grow in the more wetland areas. This plant will cause the area of moisture to create dense undergrowth of massive root systems and close off the stream flows. This plant will definitely affect the habitat and food sources of all aquatic wildlife. It will crowd out all other vegetation because it grows so dense.

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Biology of Plant: It grows 8 inches to 3 feet tall, occasionally erect, but usually spreading horizontally and forming dense mats. Leaf sheaths are flattened, very loose, smooth with hairy margins. Leaf blades are flat, roughened, 2 to 6 inches long and ¼ inch wide with rounded margins. The spikes are 1 to 3 inches long and bear clusters of 10 to 30 burs. Burs are thickly set with stiff, sharp, spreading spines. They usually contain two light brown, oval to oblong seeds.

Soil Types: Longspine sandbur favors sandy or well-drained, gravelly soils.

Environment: Longspine sandbur is a nuisance throughout most of the U.S. It grows in cultivated fields, pastures and waste areas. It grows along roadsides and sandy beach areas.

Rate of Spread: animals and machinery commonly spread Seeds.

Rec. Control Methods:

1. Manual control:

2. Chemical control: We recommend a herbicide that is used for grass species, such as Roundup or in aquatic wetlands use Rodeo.

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YELLOW TOADFLAX: (Linaria vulgaris) 

Biology of Plant: Like Dalmatian toadflax, yellow toadflax has an extensive, well-developed root system. Stems are generally 1 to 2 feet tall. Leaves are long, narrow, and pointed at both ends. They are pale green, numerous, and individually connected to the central stem. The flowers are yellow, 1 inch long with a bearded, orange throat. They have a spur like appendage. It produces egg-shaped to round fruit. Each fruit contains two compartments and many seeds.

Soil Types: It prefers moist, coarse soils.

Environment: Frequents roadsides and pastures and is an increasing problem in cultivated crops. Also found in waste areas, clear-cut and pastures.

Rate of Spread: It reproduces by seeds and by creeping rhizomes. Seed production ranges from 800 to 35,000 seeds per plant.

Rec. Control Methods:

1. Manual control by hand pulling is only effective if performed repeatedly during a season and over several years.

Chemical control can be effective if applied correctly. It should be treated in the spring when the Toadflax reaches full bloom. Due to the waxy leaf, adding a surfactant can help improve control.

2. Cultural control can control effectively if it is done in the spring and repeated so the plant does not have time to grow.

3. Biological control a leaf and flower eating moth called Calophsia lunela has been released and is being monitored by Kittitas County Noxious Weed Board.

Herbicide Control, Estimated Cost per Acre: This per acre cost depends entirely on many variables, example: backpack, ATV, truck boom, or helicopter applications. Each method has a different cost rate per acre, also depending on the type of Herbicide selected, the size of the infestation and the price paid per gallon of selected Herbicide. We can give close estimates based upon the 2002 bid price cost for ground application.

Affects on Water Quality: Same as all other Noxious weeds invading sites and affecting the habitat and wildlife areas.

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Biology of Plant: Sulfur cinquefoil is a perennial species with a woody rootstock. It produces several erect stems, which can reach one to three feet in height. The stout, leafy, hairy stems are un-branched up to the inflorescence. The leaves, which are also rough-hairy, have five to seven toothed, palmately arranged leaflets that are two to four inches long. Each flower has five light yellow petals surrounding a dark yellow center.

Environment: Sulfur cinquefoil can form monocultures over large areas of rangeland, roadside, waste places, and un-worked fields.

Rate of Spread: This species reproduces by seed, but roots can spread it if they are moved by tillage or on soil moving equipment.

Rec. Control Methods:

1. Manual control by hand pulling or chopping is effective if care is taken to remove the root crown. Mowing is not an effective control measure because the roots send up new shoots afterward.

2. Chemical control: Several selective herbicides provide effective control of cinquefoil without harming grasses. Repeated applications are needed for long-term herbicide control.

3. Cultural control: In productive areas, cultivation with annual crops will control sulfur cinquefoil.

4. Biological control: are not available at this time.

Herbicide Control, Estimated cost per acre: This per acre cost depends entirely on many variables, example: backpack, ATV, truck boom, or helicopter applications. Each method has a different cost rate per acre, also depending on the type of Herbicide selected, the size of the infestation and the price paid per gallon of selected Herbicide. We can give close estimates based upon the 2002 bid price cost for ground application.

Affects on Water Quality: Same as all other Noxious weeds invading sites and affecting the habitat and wildlife areas.

 

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HOARY CRESS or WHITE TOP: (Cardaria drapa) non-native  

Biology of Plant:  A perennial from the mustard family. Stems are simple, stout, erect and stand about 1 to 2 feet tall.  The leaves are grayish-green in color and have smooth to finely toothed edges.  The flowers are small with four petals and are white in color.  The seeds are oval, reddish brown in color and about 1 ½ inch long.  It reproduces by root rhizomes and seeds.

Environment:  It is commonly found along roadsides, in pastures, range land, field crops, and other non-crop areas.

Rate of Spread:  Its extensive root system and an abundance of seeds provide for the spread of this weed.

Rec./Control Methods:

1.    Manual control is not very successful but if there are little patches around the home hoeing and digging out roots within 10 days of plant emergence throughout the growing season can help control.

2.    Chemical control is effective if used correctly. The plant should be sprayed with foliar herbicides during its rosette stage.  Larger plants that are in full bloom can be controlled when good spray coverage is achieved.

3.  Cultural controls are not very successful in controlling this plant.  Cultivating fallow ground will eventually eliminate hoary cress if it is repeated within 10 days of plant emergence though out the season.  Close mowing also will reduce seed production but will not eliminate the infestation.  Both mowing and cultivating delay flowering and seed production.  Planting of a competitive species provide some resistance to the invasion and spread of hoary cress.

4. Biological controls are not available at this time.

Herbicide Control: This per acre cost depends entirely on many variables, example: backpack, ATV, truck boom, or helicopter applications. Each method has a different cost rate per acre, also depending on the type of Herbicide selected, the size of the infestation and the price paid per gallon of selected Herbicide. We can give close estimates based upon the 2000 bid price cost for ground application. An applicator can cover many acres over one hour of time, so this fee charge will vary according to the difficulty of the terrain and time involved. 

Affects on Water Quality:  Whitetop has not typically grown along lakes or rivers, but will grow in the more wetland areas. This plant will cause the area of moisture to create dense undergrowth of massive root systems and close off the stream flows. This plant will definitely affect the habitat and food sources of all aquatic wildlife. It will crowd out all other vegetation because it grows so dense.

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