Okanogan County Noxious Weed Control Board

New Invaders

Noxious Weeds that have not been recognized by the State Weed Board as being a Class A Weed, that are new and/or established in Okanogan County, which pose a very serious threat. The Okanogan County Noxious Weed Control Board reserves the right to develop and/or coordinate a control program on these weeds and could utilize enforcement actions as outlined in RCW 17.10 for mandatory control.

Rush Skeletonweed (Chondrilla juncea L.)

Yellow Toadflax (Linaria vulgaris)

Orange Hawkweed (Hieracium aurantiacum L.)

Meadow Hawkweed (Hieracium caespitosum)

Spurge Flax (Thymelaea passerina)

Yellow Starthistle (Centaurea solstitialis)

Scotch Thistle (Onopordum acanthium) (Tunk & Methow)

Musk Thistle (Carduus nutans) (Tunk & Methow)

Oxeye Daisy (Leucanthemum vulgare)

Common Groundsel ( Senecio vulgaris L.)(Wauconda)

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Rush Skeletonweed: (Chondrilla juncea L.) non-native Picture

Biology of Plant: Rush Skeletonweed is deep-rooted creeping perennial that also reproduces by seed. Look for downwardly pointed hairs at the base of this weed. The remainder of the stem is relatively hair-free and smooth.

Soil Types: Skeletonweed is found in various soil types but does especially well in sand & gravel soils that receive from less than 10 inches to greater than 40 inches of rainfall yearly.

Environment: Skeletonweed has been found in abandoned gardens, along roadsides, grain fields, pastures and on rangeland.

Rate of Spread: The seeds are spread by wind and human activities, so this plant can spread very rapidly.

Recommended Control Methods:

1. Manual control by handpulling is not effective. When the roots are severed, they produce shoots that can reach the soil surface from depths of 4 feet.

2. Chemical control can be effective if applied correctly. It should be treated in the spring before the Skeletonweed reaches full bloom. Due to the waxy leaf, adding a MSO & silicone blend surfactant can help improve control.

3. Cultural control is not recommended as tilling merely spreads the plant. Small root segments can establish additional plants.

4. Biological control the gall midge, Cystiphora schmidt, attacks all biotypes.

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 2004 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.

YELLOW TOADFLAX: (Linaria vulgaris) AKA: BUTTER & EGGS

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.

2. 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.

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

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

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

HAWKWEEDS (Hieracium aurantiacum) non-native

ORANGE HAWKWEED: PICTURE

MEADOW HAWKWEED

Biology of Plant: Hawkweed is a perennial plant with a fibrous root system. It can reproduce by seeds, stolons, rhizomes, and buds on the roots. The weed can produce seeds both with or without pollen.

Soil Types: it prefers soils that are well-drained, coarse-textured, and low in organic matter.

Environment: It is found in pastures and hayfields, mountain meadows, forest clearings, roadsides and abandoned farmland.

Rate of Spread: This weed can spread very rapidly. Once established, it quickly expands it’s colony with vigorous stolon growth forming dense patches with as many as 3,200 plants per square yard

Rec./Control Methods:

Manual control is not recommend with this plant and actually encourages growth from it’s root system.
Chemical control has proven very effective if done correctly. Spraying should be done while the plant is still young and actively growing. There is a good selection of herbicides that work very effective on this weed and can also provide a site specific treatment.
Cultural control crop cultivation can be an excellent way to control hawkweed, since the crops can out compete the weed.
Biological control none known at this time, although testing is currently being done.

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

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SPURGE-FLAX: (Thymelaea Passerina) non-native

Biology of Plant: Spurge-Flax plants are slender, erect annuals that grow about 1 to 3 feet tall. The plants are green in color, but in the fall when the plant has entered into its winter dormancy they are then a reddish-brown color. The stems are simple and branched. The leaves are alternate and linear. The flowers are green in color and lacking in petals.

Rec./Control Methods:

Manual control hand pulling may be effective, no known studies at this time.

Cultural control not known

Biological control none at this time.

Chemical control chemical control of Spurge Flax is difficult to due to lack of surface area of the small, leathery leaves. Use of a MSO/Silicone blend surfactant is recommended.

Re-vegetative practices are highly recommended. Spurge-Flax is a top priority weed for Okanogan County Noxious Weed Board and eradication is required. It has only been found in one spot in the county. The closest recorded sites are in Nebraska.

Herbicide Applications has had an excellent result and control on this invasive specie. Our office conducted 2 years of test plots with a variety of herbicides to attain the maximum control.

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

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YELLOW STARTHISTLE: (Centuara solstitalis) Knapweed Family PICTURE

Biology of Plant: is a two stage annual. The first stage is a rosette that consists mainly of deeply lobed leaves with pointed tips. The second stage of the plant is 2 to 3 feet tall. Stems are rigidly-branched from the base and covered with white, cottony wool. Flower heads are bright yellow in color, located singly on ends of branches, and armed with sharp straw-colored thorns up to ¾ inch long. It has a stout tap root and spreads primarily by seed.

Soil Type: various types

Environment: Yellow starthistle readily colonizes different soils over a broad range of environmental conditions. It is not a common weed on cultivated land nor irrigated pasture. It prefers open sites in the sun. Yellow starthistle prefers lower elevation, warmer sites favorable to cheat grass and other annual vegetation.

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.

Rec./Control Methods:

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, 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 2004 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.

SCOTCH THISTLE: (Onopordum acanthium) non-native PICTURE

Biology of Plant: is a two stage biennial. The first stage of the plant is a rosette of spiny, thistle-like leaves. The second stage of the plant can grow 8-12 foot tall. The stems are upright, branched and have broad spiny wings. The leaves are large, spiny and covered with fine hair. The plant is blue-green in color with a purplish to pink flower. Flowers are numerous and are 1 to 2 inches in diameter. It reproduces primarily by seed.

Environment: best adapted for sites along rivers and streams but can be a problem in pastures, meadows, burned areas, roadways, campsites railroads, and abandoned fields.

Rate of Spread: This weed is aggressive dominating other plants with its size. Once established it’s rigid growth and spines protect the plant against grazing and trampling. The seed contains a chemical that delays germination thus allowing the seeds to germinate for up to five years. This chemical also stops the germination of other nearby plants. One scotch thistle plant can produce 20,000 seeds.

Rec./Control Methods:

Manual control digging with a shovel and hand pulling is effective if completed before the plant is in full bloom. Manual control must be done a minimum of two times during the growing season.

Chemical control has proven very effective if done correctly. Spraying should be done early while the plant is still young, for the most cost effective use of herbicides.
Cultural control should be used in conjunction with another method of control. Reseeding and planting competitive plants, good land management, and grazing young plants with sheep can help control scotch.

Biological control practices have not been successfully developed to control this pest, but the weed office has released bio-agents the same as Musk thistle.

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 2004 bid price cost for ground application.

Affects on Water Quality: Scotch thistle increases 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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MUSK THISTLE: (Carduus nutans L.) non-native PICTURE

Biology of Plant: Biennial and winter annual, tap root, spreads by seed, 1,000 seeds per head, 50 to 100 heads per plant, 7-8 feet tall, 90% germinate the first two years, viable 10-15 years.

Environment; prefers open direct sunlight, but will also grow in forested, shaded and moist covered areas, Musk adapts to a variety of environmental areas. Musk seems to grow in draws, steep hillsides, rocky bluffs and open slopes.

Rate of Spread; This weed is aggressive and moves rapidly moves into rangeland, waste areas, pastures and roadsides. No other documentation is found on the rate of spread for this plant.

Rec./Control Methods;

Manual control using a shovel, is effective. We have controlled many thousands of acres with our County Hand-pull crews and it has worked very effectively.

Chemical control has proven to be extremely effective in controlling and preventing the spread for a longer period of time. The population of this noxious weed can be rapidly reduced. Spring and Fall are the ideal times to apply Herbicides, site selected herbicides can increase the growth of native vegetation and grasses to out compete the Musk thistle.

Cultural method can control Musk thistle. It does not become a problem in spring planted crops because cultivation kills the young seedlings. Mow hay fields before the seed forms to reduce the thistle population. Vigorous stands of grass also offer competition.

Biological Control Rhinocyllus Conicus (seed head weevil), & Cheilosia corydon (crown weevil)

Affects on Water Quality; Musk thistle usually does not grow along stream banks to cause erosion effects, but it will grow in some wetlands and crowds out native vegetation and wildlife habitat.

Oxeye Daisy: (Leucanthemum vulgare) PICTURE

Biology of Plant: : It is a perennial herb, 1 to 3 feet tall, with shallow, branched rhizomes and adventitious roots. The stems, which arise from upturned rhizomes or buds on the root crown, range from hairless to slightly hairy. The prostrate, basal stems can root, while the other stems are erect and simple to slightly branched. Cotyledons open above ground and wither soon after the first leaves form. The toothed, spatula-shaped to round basal leaves occur on long stalks. The stem leaves are alternate and lack stalks; they are lance-shaped to ligulate, with coarse teeth and often have a few lobes at the base. Flowers are showy and daisy-like, with 20 to 30 white ray flowers and numerous, bright yellow disk flowers. Flower heads are usually solitary and grow on long, terminal stem; heads average 1 to 2.2 inches in diameter. Involucral bracts are narrow with a dark brown, scarious margin. The fruit is a dry, indehiscent achene that is circular in outline and lacks a pappus. The entire plant has a disagreeable odor when crushed.

Environment: It aggressively invades fields, where it forms dense populations, thus decreasing plant species diversity. In areas of heavy infestations, bare soil is more common, which increases the potential for soil erosion.

Rate of Spread: Oxeye daisy seeds will germinate as soon as they are dispersed. It can spread both vegetatively and by seed.

Rec/Control Methods:

Manual control is not recommended, because Oxeye Daisy is a perennial. Handpulling can stimulate root growth and send up many new shoots. If only a few plants are present handpulling is an option and will eliminate plants if one makes the commitment to monitor for new plants to monitor for new plants throughout the growing season.

Cultural control intensive cultivation will easily eliminate infestations of Oxeye Daisy because of its shallow root system. Re-seeding after cultivation will provide competition for any existing shoots or seeds from the Oxeye Daisy.

Chemical control there are several herbicides available that will provide site specific control of Oxeye Daisy. Contact Anna at the Noxious Weed Office for site specific recommendations.

Biological control there are no known effective Biocontrol agents at this time.

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

Common Groundsel: (Senecio vulgaris L.)

Biology of Plant: It is a winter annual, sometimes biennial, though it may germinate in all seasons. It grows from 4 to 18 inches tall. The leaves are deeply lobed with toothed margins and may be smooth to hairy or woolly. Leaves have little or no leaf stalk, and are arranged along the stem in a spiral. Basal leaves usually are purplish on the under surface, 1 to 4 inches long, and 1/2 to 1 1/2 inches wide. Stems are hollow and rather succulent. Groundsel produces abundant seeds, which spread by floating on the wind with their parachutes of hairs. One plant can produce an many as one million seeds in a season. Groundsel is toxic to livestock. The toxins are four pyrrolizidine alkaloids, which cause irreversible liver damage.

Environment: It infests many crops, including forages, cereals, mint, berries, and row crops, as well as ornamentals and vegetable crops.

Rate of Spread:

Rec./Control Methods:

Manual control handpulling of Common Groundsel can be effective if one wants to make a season long commitment to pull new plants as they emerge.

Cultural control cultivation, prior to seed formation, can eliminate Common Groundsel plants. However, freshly tilled soil provides an excellent opportunity for dormant seeds to germinate and become established..

Chemical control there are several herbicides available that will provide control of Common Groundsel. When Common Groundsel is found in alfalfa field, which are susceptible to Groundsel invasion, your choices of herbicide are rather limited.

Biological control the larvae of the Cinnabar Moth, an insect that is released to provide control of Tansy Ragwort, will eat Common Groundsel. They are not capable of providing significant control because they are only present form June through August and the Common Groundsel will produce seed from early Spring to late Fall.

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

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