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Perennial, flowering July through September. Yellow flower about 3/4 inch in diameter with 7 to 15 petals. Coarse downbent hairs on the lower 4 to 6 inches of the stem; Plant is 1 to 4 feet tall with almost no leaves.
An aggressive plant in both rangeland and cropland, particularly in light texture soils. Extensive efforts have been made to eradicate, but new sites are found each year in Eastern Oregon.
Herbicides are available and effective. Follow up treatment will be necessary for 2-3 years, or longer. Pulling is NOT recomended, nor is cultivating through live roots. Small root segments can establish additional plants.
A midge, a mite and a rust are available in the Pacific NW. These agents by themselves have not been able to stop the spread of rush skeletonweed.
Rush Skeletonweed Control in Late Fall - Excellent
Fall is an excellent time to treat skeletonweed sites in your fields and scab patches even if you treated earlier in the season. I found great success treating at this time of year. I first tried a late fall treatment in the 1980's. A 10 acre site of skeletonweed was discovered in November and we wanted to treat it aggressively. An application of Tordon 22K was made. Control was excellent. Only a few scattered plants came back in the following years. Increased reports of rush skeletonweed in cropland this year suggest to me that we should be more aggressive in our control and survey efforts.
The Oregon Department of Agriculture's Weed Control program now prefers the late fall treatment over other treatment times. They field survey with their GPS (Global Positioning System) units during the summer months when plants are easier to see. They use GPS coordinates to return to the sites in the late fall to make herbicide treatments. (If you were looking for a reason to invest in a GPS unit this would work.) Otherwise a fiberglass fencepost could be used to mark the location. Treatments can be made in November and December as long as weather permits.
Rush skeletonweed is a deep-rooted, creeping perennial that also reproduces by seed. Its yearly cycle of growth starts in the fall when seeds germinate or crown buds grow into rosettes. The vertical taproot of established plants penetrates more than 10 feet deep. Lateral roots branch off the main taproot and form daughter plants. Tillage will drag root fragments to non-infested areas.
Biological control agents are established on rush skeletonweed in the Pacific Northwest. They have not proven to be very effective on the biotype of skeletonweed found in our area.
Remember to use pesticides with care. Do not treat on frozen ground. Always read and follow label instructions.