Weed of the Week: Rush Skeletonweed
Active harvest and tillage is critical to the success of farm operations, but when an invasive plant like rush skeletonweed (Chondrilla juncea)
comes into the path of machinery, farmers can expect down time, loss of productivity, and if allowed to continue its spread, a drastic reduction in forage crop yields.
When wiry, fiborous stems of rush skeletonweed plants are cut or broken, they ooze a milky latex sap that gums up harvesting machinery. These hardy plants are also referred to as gum succory, devil’s-grass, naked weed or hog-bite. Plant fragments, resulting from contaminated cultivation machinery, are responsible for the majority of its spread into new areas.
Rush skeletonweed is a mass of thin, milky fluid-filled stems and small yellow flowers, growing just over one metre in height at maturity. Wiry stems are covered with stiff, reddish-brown hairs at the base. Barely visible narrow leaves give it a “skeleton-like” appearance.
Once established, rush skeletonweed is known to drastically reduce crop yields by out-competing forage crops for soil moisture and nitrogen. In Australia, crop yields have been reduced by 50-70 percent, with some fields later converted to rangeland. Since its introduction to Australia in 1935, the expansion of rush skeletonweed has resulted in estimated annual losses to wheat production in excess of $30 million.
Rush skeletonweed is native to regions of Europe, Asia, and Africa, and was accidentally brought to the United States as a contaminant of fodder in 1914.
This aggressive invader has spread throughout much of the world with its adaptability to a wide range of climatic and environmental conditions. It poses a serious threat to British Columbia rangelands and other agricultural resources, including both dryland and irrigated cereal production, according to Agriculture and Agri-food Canada.
Considered provincially noxious under the BC Weed Control Act, infestations are known to occur in gravel pits, cropland, rough pasture and rangeland, as well as along transportation corridors. Infestations occur in the Vernon area, Crescent Valley, Kimberley, Windermere, and Creston. It is a major concern in the Kootenay and Okanagan regions.
Infestations cover thousands of hectares in the United States, and since it has no natural predators in North America, this invasive plant will continue to spread if it is not controlled. Over two million hectares have been infested in the Pacific Northwest, and it is currently spreading at a rate of 100,000 acres per year.
Invasive plants grow rapidly and spread quickly. Rush skeletonweed plants can produce 20,000 parachute-like seeds that travel easily with wind, water, animals, and people. Each seed has a ‘pappus,’ or individual ray floret which is capable of carrying seeds along wind currents up to 20 miles. Roadside populations of rush skeletonweed are established when the seed is moved along transportation routes. Horizontal roots also aid reproduction, with root fragments as deep as four feet that will regenerate new growth if not entirely removed. Though it rarely invades healthy rangeland, this invasive plant will grow in waste places and in overgrazed areas.
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