Noxious Weed Identification and Prevention FGV-00144 Definition The Alaska Administrative Code defines noxious weeds as any species of plants, either annual, biennial, or perennial, reproduced by seed, root, underground stem, or bulblet, which when established is or may become destructive and difficult to control by ordinary means of cultivation or other farm practices. The main differences between a common weed and a noxious weed are: the noxious weed s high capacity for destruction and the extreme difficulty in controlling or eradicating the invading species. Impact The invasion of noxious weeds onto private and public lands causes substantial economic loss and ecological damage. Most noxious weeds are not native to the United States and have no natural controls in this country. Some were introduced through contaminated seed while others were intentionally introduced without the knowledge of their future destructive nature. Left to spread without control these introduced plants can create severe problems for farmers, land managers, home owners and recreation ists. The long term effects of uncontrolled spread can result in higher crop and livestock production costs, loss of native plants, degradation of wetlands and destruction of wildlife habitat. At risk are agricultural lands, forests, wilderness areas, parks and recreational sites. Introduction and Spread Common sources for the introduction and spread of weed seed include the purchase, transportation and utilization of contaminated seed, forages and plant materials. The use of clean materials is a grower/user responsibility and an important step in limiting the spread of noxious weeds. Additionally, with free access to large amounts of unfenced public and private land in Alaska, the spread of weeds by human recreational activities is a potentially serious problem. Regulations Regulation and control of plant pests is authorized under Title 3 of the Alaska State Statutes. The Alaska Division of Agriculture is authorized to prevent the importation and spread of pests that are injurious to the public interest and for the protection of the agricultural industry. Regulations relating to noxious weed control are found in Title 11 Chapter 34 of the Alaska Administrative Code. The rules for establishment of quarantines, inspections, noxious weed lists (see following pages for Noxious Weeds in Alaska) and control measures are all provided for in current state regulations. Private and public land owner control of noxious weed infestations is encouraged in lieu of government funded programs. Public education rather than enforcement is the preferred method for dealing with noxious weed problems.
1. Photo courtesy of Weeds of the West 2. Photo courtesy of Weeds of the West 1. Canada thistle (Cirsium arvense) Perennial, spread by seed and creeping roots; stems erect to 4 feet, branched near top; leaves alternate, irregularly lobed, spiny, dark green on top, white-hairy underneath; flowers white, rose or purple, diameter to 3 4 inch, grouped in small clusters. 2. Perennial sowthistle (Sonchus arvensis) Perennial, spread by seed and creeping roots; stems erect to 5 feet, hollow with milky sap, branched near top; leaves alternate, crowded on lower half of stem and scarce near the top, more or less lobed with mildly prickly margins, leaves clasp stem at base; flowers bright yellow, diameter to 2 inches, grouped in small loose clusters. 3. Quackgrass (Agropyron repens) Perennial, spread by seed and creeping roots; stems erect to 3 feet, upper portion smooth, lower sparsely hairy; leaves 1 4 to 1 2 inch wide, sparse hair on upper surface, underside glossy; claw-like appendages where leaves clasp stem; flowers arranged on slender 6-10 inch spike, flower clusters (spikelets) arranged in two long rows, borne flat-wise to stem. 4. Field bindweed (Convolvulus arvensis) Perennial, spread by seed and creeping roots; stems slender vine-like and twining to 4 feet long; leaves alternate, arrowhead-shaped, length to 2 inches; flowers white to pinkish, funnel-shaped, diameter to 1 inch. 3. Photo courtesy of Weeds of the West 4. Photo courtesy of Weeds of the West
5. Photo courtesy of Weeds of the West 6. Photo courtesy of Weeds of the West 5. Hoary cress (Cardaria draba) Perennial, spread by seed and creeping roots; stems erect to 2 feet, branched near top; leaves alternate, lance-shaped, grayish-green, length to 3 inches, finely toothed edges, covered with soft fine hairs; flowers white, 4 petaled, diameter to 1 4 inch, form dense flat-topped clusters. 6. Russian knapweed (Centaurea repens) Perennial, spread by seed and creeping roots; stems erect to 3 feet, often branched from base, leaves alternate, length to 4 inches, lower leaves lobed or sharply toothed, upper leaves not lobed but finely toothed; flowers borne singly at end of branches, diameter to 1 2 inch, color-pink to lavender. 7. Austrian fieldcress (Rorippa austriaca) Perennial, spread by seed and creeping roots; stems slender, erect or sprawling to 3 feet, branched near top; leaves alternate, smooth, length to 3 inches, lower leaves more distinctly toothed than upper; flowers bright yellow, 4 petaled, diameter to 1 8 inch, in loose clusters at tips of branches. 8. Leafy spurge (Euphorbia esula) Perennial, spread by seed and creeping roots; stems thickly clustered, erect to 3 feet; leaves alternate, narrow, lance-shaped, length to 4 inches; flowers yellowish-green, diameter 1 8 inch, in numerous small clusters, each cluster surrounded by a pair of heart-shaped yellow-green bracts (leaves); plant contains a milky sap. 7. Photo courtesy of Cindy Roché, Washington State University 8. Photo courtesy of Weeds of the West 3
9. Photo courtesy of Weeds of the West 10. Photo courtesy of Jerry Doll, University of Wisconsin 9. Blue lettuce (Lactuca pulchella) Perennial, spread by seed and creeping roots; stems erect to 4 feet; leaves alternate, smooth, bluish-green, lance-shaped on upper stem, lower leaves deeply notched, length to 6 inches; flowers blue to purple, diameter to 1 1 4 inch; plant contains a milky sap. 10. Horsenettle (Solanum carolinense) Perennial, spread by seed and creeping roots; stems erect to 4 feet, sometimes branched, covered with prickly hairs and spines; leaves alternate, length to 7 inches, coarsely toothed, covered with tiny hairs, long spines down the midrib and veins on the lower leaf surface; flowers blue, violet or white, star-shaped, 5 petaled, diameter to 1 inch, look like potato flowers. 11. Smallflower galinsoga (Galinsoga parviflora) Annual, spread by seed; stems erect or spreading, branched, to 2 1 2 feet; leaves opposite, oval, pointed at the tip with finely toothed edges, surfaces mostly smooth, length to 3 inches; flowers white, diameter to 1 2 inch, in small loose clusters at tips of branches. 12. Hempnettle (Galeopsis tetrahit) Annual, spread by seed; stems erect, hairy, branched, to 3 feet; leaves opposite, lance-shaped, oval at leaf base, hairy above and below, length to 4 inches, with rounded or pointed teeth; flowers white or pink with purple markings, diameter to 1 2 inch, borne at the juncture of the upper leaves and stems. 11. Photo courtesy of Jerry Doll, University of Wisconsin 12. Photo courtesy of Saskatchewan Department of Agriculture 4
Integrated Pest Management (IPM) The focus of IPM is on long-term prevention or suppression of pests. The integrated approach to weed management incorporates the best suited cultural, biological and chemical controls that have minimum impact on the environment and on people. It is important to understand that IPM is not pesticide-free management. However, a successful IPM program should result in the most efficient use of pesticides if and when they are needed. Preventing Spread Protecting land that is not presently weed infested is the single most important management goal. The purchase of weed free seed, forages and plant materials can help to prevent the introduction of unwanted plants. Once noxious weeds are identified on agricultural land, their spread can be slowed by limiting traffic through the infested area and by thoroughly cleaning equipment and vehicles traveling between fields. Uncomposted manures that are known to contain weed seed should not be spread as fertilizer. New infestations should be treated immediately to minimize the cost of cleanup. Weed seed is often spread by human recreational activities. Suggestions for limiting this type of spread include: not driving or camping in weed infested areas. Weed seeds can easily attach to vehicles, tires and camping gear. Before moving on, be sure to shake out tents, sleeping bags and clean your vehicle if you have been in areas which contain noxious weeds. If pack animals or dogs are being used for transportation in the back country, use clean, weed free bedding and feed. Seeds contained in feed or bedding can be lost along the trail and start new populations in remote areas where control measures are difficult to apply. Before returning home from a backcountry trip remember to clean seed from your animals hooves and coats. Don t pick the flowers of unknown plants or transplant wild flowers that can t be identified. Noxious weeds can be spread by taking home bouquets or plant materials for landscaping. If a weed infested area is found, let the land owner or management agency know so they can take steps to control the weeds. Control In areas where prevention has failed, control may be necessary. There are a number of questions that must be answered before the proper control measures can be determined. What is the invading plant? Is its presence threatening? What are the control options for the site as well as for the weed? How effective are the available controls? What is the most cost effective, low impact practice available? For further information on the control of specific weeds please contact your local Cooperative Extension Service district office. Acknowledgments We would like to express our sincere appreciation to Ed Kern, Alaska Division of Agriculture; Jerry Doll, University of Wisconsin; Cindy Roché, Washington State University; the Saskatchewan Department of Agriculture; and to the authors of Weeds of the West, and Weeds and Poisonous Plants of Wyoming and Utah, for their contributions to this publication. Prepared by Mary Comeau, IPM Agricultural Program Manager and Wayne Vandre, Pest Control Programs Coordinator. 5
Visit the Cooperative Extension Service website at www.uaf.edu/ces 5-96/WGV/1000 Reprinted July 2006 The University of Alaska Fairbanks Cooperative Extension Service programs are available to all, without regard to race, color, age, sex, creed, national origin, or disability and in accordance with all applicable federal laws. Provided in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Anthony T. Nakazawa, Director, Cooperative Extension Service, University of Alaska Fairbanks. The University of Alaska Fairbanks is an affirmative action/equal opportunity employer and educational institution.