Ecology and Management of Rush Skeletonweed (Chondrilla juncea L.)

Invasive Species Technical Note Number MT-25

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Invasive Species Technical Note Number MT-25 (PDF; 177 KB)

Jim Jacobs, Invasive Species Specialist and Plant Materials Specialist NRCS, Bozeman, Montana
Kim Goodwin, Weed Prevention Coordinator Montana State University, Bozeman, Montana

Abstract

Rush skeletonweed, a member of the sunflower family (Asteraceae), is an herbaceous perennial with a rosette very similar to that of dandelion. The downward pointing, stiff hairs on the lower four to six inches of the flowering stem are a good identifying feature. It reproduces by seed and root sprouts. One flower stem 1.6 to 3.3 feet (50 to 100 centimeters) tall bearing small yellow flowerheads is produced per rosette in early summer. Each flower is capable of producing nine to 12 seeds and plants can produce 1,500 or more seeds that are fully developed 13 to 15 days after flowering. Plants five to seven weeks old or older are capable of vegetative reproduction from root buds.

Native to Asia, the Mediterranean, and North Africa, rush skeletonweed was first found in a Sanders County tree plantation in 1987 and has subsequently been reported from Flathead, Lincoln, Sanders, and Treasure counties in Montana. Rush skeletonweed occupies about 700 acres in northwestern Montana. A new population in southern Ravalli County was reported in 2006. And in 2007, an invasion was detected in eastern Montana along a highway in Treasure County. Establishment is most likely on disturbed sites, particularly those affected by wildfire and cheatgrass invasion. Populations are found most often on low-nutrient, coarse-textured soils in open forest types and shrub-steppe plant communities. Rush skeletonweed is a problem in wheat and grain fields and rangelands where it reduces yields and forage production (see Figure 1).

Figure 1. The rush skeletonweed population (foreground) is part of a several thousand acre infestation in Idaho. Photo by Brad J. Gamett, Butte County Weed Department, Idaho, used with permission.

Because it is a relatively new invader in Montana, herbicides are most commonly recommended for rush skeletonweed control. Herbicides most effective for root kill are picloram, clopyralid, aminopyralid, and dicamba. Hand pulling several times each growing season might be effective on newly established populations. Large infestations that cannot be eradicated should be grazed to prevent flowering and seed production. Cattle will graze early flowering plants, horses will graze plants in the vegetative stage, and sheep will graze plants in the rosette to flowering stage. Biological control agents are effective in certain locations. Preventing large-scale disturbance and maintaining a competitive plant community are important to prevent invasion and to reduce spread. Ecosystem management to prevent invasion includes early control of cheatgrass, since primary invasions of cheatgrass drive both secondary invasions of rush skeletonweed and the cheatgrass-wildfire cycle, which promotes additional expansion of rush skeletonweed.

Plant Biology

• Identification
• Life History, Habitat, Spread and Impacts

Management Alternatives

• IPM, Chemical, Mechanical and Cultural Control
• Biological Control and Revegetation

References

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Last Modified: 08/24/2009