Integrated Weed Control Project

Puccinia chondrillinaPuccinia

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Common Name

Rush skeletonweed rust fungus

Weed Impacted

This fungus attacks rush skeletonweed.  Fall and spring infection of basal leaves can result in premature death of plants, especially younger plants.  Open lesions on the plants cause wilting, reduce photosynthesis, and contribute to a decrease in overall plant health.  Infected stems are stunted and deformed, producing few branches or flowers.

Agent Description/Field Identification

Infected plants will appear spackled with rusty, cinnamon brown-colored spots and splotches.

Life Cycle

This fungus has several stages of spore production.  From spring to fall, circular, rust-colored spots (uredia) develop on all aboveground parts of the plant and release infective spores called urediospores.  Open lesions (telia) form at the bases of stems in the fall and produce teliospores which are dormant until spring.  These spores germinate on rosette leaves and form yellowish clusters (pycnia) that will produce more spores called pycniospores.  Pycniospores yield aecia and aeciospores, which then complete the cycle by germinating and producing the rusty-brown uredia. 

Availability

This agent is readily available in Washington, Oregon, Idaho, and California.  Infective stems are harvested throughout the summer.  Infected rosettes can be dug and transplanted among uninfested plants in the spring and fall. To inquire about availability and to request this biocontrol agent, please download, complete and submit this form.

Comments

P. chondrillina was the first exotic plant pathogen used successfully for the biological control of weeds in North America.  It is well established at many sites throughout the Pacific Northwest and California.  A few populations of rush skeletonweed are resistant to one strain of the fungus, but European scientists are working to find or develop strains that can infect those plants.

Using the Agent: Integrated Weed Management (IWM)

P. chondrillina may be used in combination with the rush skeletonweed gall mite (Eriophyes chondrillae) and/or the skeletonweed gall midge (Cystiphora schmidti).  Biocontrols should only be released when skeletonweed infestations are large and immediate eradication is not the primary objective.

Individual plants and smaller, satellite populations may either be hand-pulled, dug, or sprayed.  Herbicides should not be applied where biocontrol agents have been released. Consult with your county weed office, Extension office or an IWM practitioner to determine which herbicide treatments are safe and appropriate. 

Any management of rush skeletonweed should involve revegetation with native or other desirable plants.  Competition between plants stresses weeds and can allow for more effective treatment.  To learn more about revegetation and IWM, click here.

References

Coombs, E. M., J. K. Clark, G. L. Piper, and A. F. Cofrancesco, Jr. 2004. Biological Control of Invasive Plants in the United States. Western Society of Weed Science, Oregon State Univ. Press, Corvallis.

McCaffery, J. P., G. L. Piper, R. L. Callihan, and E. M. Coombs. 1996. Collection and redistribution of biological control agents of rush skeletonweed. University of Idaho Extension Publications. Bulletin 782.

Photo Credit

Puccinia chondrillina - Gary L. Piper, Washington State University, bugwood.org (ipmimages.org), http://www.ipmimages.org/images/768x512/0022096.jpg

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