United States Department of Agriculture Field Guide for Managing Rush Skeletonweed in the Southwest Forest Southwestern Service Region TP-R3-16-22 Revised June 2017 Cover Photos Top left: Utah State University Archive, Utah State University, Bugwood.org Top right: Richard Old, XID Services, Inc., Bugwood.org Lower center: Utah State University Archive, Utah State University, Bugwood.org In accordance with Federal civil rights law and U.S. Department of Agriculture (USDA) civil rights regulations and policies, the USDA, its Agencies, offices, and employees, and institutions participating in or administering USDA programs are prohibited from discriminating based on race, color, national origin, religion, sex, gender identity (including gender expression), sexual orientation, disability, age, marital status, family/parental status, income derived from a public assistance program, political beliefs, or reprisal or retaliation for prior civil rights activity, in any program or activity conducted or funded by USDA (not all bases apply to all programs). 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Submit your completed form or letter to USDA by: (1) mail: U.S. Department of Agriculture, Office of the Assistant Secretary for Civil Rights, 1400 Independence Avenue, SW, Washington, D.C. 20250-9410; (2) fax: (202) 690-7442; or (3) email: [email protected]. USDA is an equal opportunity provider, employer and lender. Printed on recycled paper Rush skeletonweed (Chondrilla juncea L.) Sunflower family (Asteraceae), Lactuceae tribe (Cichorieae) Rush skeletonweed is an invasive plant in the Southwest is persistent and becomes increasingly tough as it that has been listed as a noxious weed in Arizona. This matures; 16 to 48 inches tall. field guide serves as the U.S. Forest Service’s • Exudes a white milky substance from cut, broken, or recommendations for management of rush skeletonweed in damaged stem, leaf, and root surfaces. forests, woodlands, and rangelands associated with its • Small, bright yellow flowers from May until first Southwestern Region. The Southwestern Region covers frost; flowers are located on the end of the branch Arizona and New Mexico, which together have 11 national (terminal) or between the branch and stem (axillary). forests. The Region also administers 4 national grasslands The flowers may be directly attached to the branch located in northeastern New Mexico, western Oklahoma, (sessile) or be on short stalks (pedicelled); flowers and the Texas panhandle. may also be found in clusters of 2 to 5. Instead of the disk and ray flowers common to other species in Description the Asteraceae family, rush skeletonweed has only Rush skeletonweed (synonyms: skeletonweed, hogbite, one type of flower (ligulate). Heads have 9 to 12 gum succory, devil’s grass, naked weed) is a wiry-looking strap-shaped flowers; each flower has 5 fused petals perennial that was introduced from Eurasia. Given that have a toothed appearance at the tip. favorable conditions, the species can spread rapidly and • Reproduces mainly vegetatively via adventitious form dense infestations. Thus far, three distinct genotypes buds near the top of the taproot; lateral roots near have been identified with each genotype differing slightly surface can become rhizome like and also have root in the appearance of the rosette leaves and branching. In buds; dense patches of cloned plants may form in the rosette stage, rush skeletonweed resembles common response to damage. dandelion (Taraxacum officinale) or chicory (Cichorium intybus L.). After bolting, rush skeletonweed can be • Seed is asexually produced (15,000 to 20,000 seeds distinguished by its brown, downward-pointing hairs near per plant). Seeds are oblong, ribbed achenes with a the base of the flowering stem. pappus of numerous soft bristles. Depending on soil conditions, seeds may remain viable from 6 months Growth Characteristics to more than 8 years. Seed quickly germinates in • Long-lived perennial herbaceous plant; mimics a response to available moisture; seedling mortality biennial (overwinters as a rosette). rate is high should extremely dry conditions occur immediately after establishment. • Deep and stout taproot; rapidly grows overwinter to a depth of 3 to 7 feet. Ecology • Rosette base with 2 to 5 inch hairless reddish-brown Impacts/Threats leaves with purplish incised margins and lobes Rapid spread of rush skeletonweed is potentially high once pointing backward toward the leaf base; lobes are so it is introduced to an area with favorable growth deep the leaf looks nearly pinnate. conditions; it is difficult to eradicate once established. The • Produces bright green or yellowish, wiry, erectly weed diminishes preferred rangeland forage and reduces branching flowering stems in spring; stem has few plant and animal diversity. It also causes lost production in narrow, linear leaves with entire margins and brown, wheat fields, and its persistent flower stems are so tough downward-pointing hairs at its base. Flowering stem they can hamper harvest machinery. 1 Site/Distribution Management Rush skeletonweed adapts to a wide range of climate Prevention along with early detection are the most cost- zones and environmental conditions. However, it is limited effective management actions against this invasive plant. by the amount of calcium and phosphorous available in the An integrated management strategy that combines several soil. Generally, rush skeletonweed prefers well-drained control methods should be implemented to contain, sand or gravel and does not fare well in waterlogged or reduce, or eradicate populations of mature rush heavy clay soils. It also favors areas with 10 to 40 inches skeletonweed. As with other perennial weeds that of precipitation, preferably with moisture available at the primarily reproduce vegetatively, treatment should involve onset of the cool season and in the spring. It can invade attacking the extensive root system. roadsides and other transportation corridors, rotational pastures, croplands (especially grain fields), waste areas, The following action measures should be considered when and rangelands. planning an overall management approach: The species is now widespread in western States including • Maintain healthy plant communities and the Washington, Oregon, Idaho, Montana, and California. An presence of ground litter to prevent or limit rush isolated, yet expanding population has been found in the skeletonweed infestations. This may involve Grand Canyon National Park in Arizona. improving grazing management practices to prevent excessive grazing and the reseeding of disturbed Spread areas with desirable forbs and grasses. Although rush skeletonweed produces wind-dispersed seed, it spreads mainly through vegetative propagation that • Use certified weed-free seed and hay; use pellets for arises from adventitious buds. Root fragments as little as horses used in backcountry areas. about one-half inch in length can produce new plants even • Eradicate new populations of rush skeletonweed as if buried in soil to a depth of 3 feet. Seed or root fragments early as possible. may be introduced into new areas via transportation • Detect, report, and map large infestations. Keep corridors such as roadways and train tracks. Rush annual records of reported infestations. skeletonweed may also spread through transported hay that is not certified to be weed-free or by attachment of • Combine cultural, biological, and chemical methods propagules that adhere to the undercarriages of off-road for effective rush skeletonweed control. vehicles and road maintenance equipment. The most rapid • Implement a monitoring and follow-up treatment spread appears to occur at mid-elevation areas. plan for missed plants and seedlings. Invasive Features Table 1 summarizes management options for controlling While rush skeletonweed is capable of spreading rapidly, it rush skeletonweed under various situations. Further details does not typically invade stands of native vegetation in on these management options follow the table. Choice of good condition. Open plant communities, drought, and soil individual control method(s) for rush skeletonweed disturbance from human or animal activities can increase depends on the extent and density of infestation, current the likelihood for invasion. The competiveness of rush land use, and site conditions (weather, accessibility, skeletonweed is believed to be related to its ability to terrain, other flora and fauna present, etc.). The specific reproduce vegetatively in response to damage such as biotype of rush skeletonweed present should also be severed roots, stems cut near the base, and fire. Once considered as each one may respond uniquely to different established,