Did you hear about North America’s newest weed pest? It was found near Yakima.
We need everyone to help find, contain and eradicate a parasite that attacks sunflowers, and has been found on tomatoes, eggplant and tobacco plants.
Orobanche cumana, also known as sunflower broomrape, is a member of a family of plants that lack chlorophyll. They rely on a host plant for nutrients and water, which depletes the energy and productivity of the host.
There are four native Orobanche species in the Northwest that grow on native plants such as sagebrush, buckwheat, ocean spray and arbutus. A few other native varieties grow in other areas of the United States.
Orobanche cumana is not a native variety and is aggressively invasive.
Background
According to last year’s state Department of Agriculture statement, this marks the first known occurrence of this destructive and highly invasive parasitic weed in North America.
The pale, leafless flower spike of sunflower broomrape shows its distinctive bluish-purple blooms. The invasive parasitic plant has been identified near Yakima and should be reported if suspected.
Photo courtesy of Yakima County Noxious Weed Board
The parasitic plant was discovered by a homeowner in the Yakima area and later confirmed by the WSDA State Plant Pathology and Molecular Diagnostic Lab and USDA Animal and Plant Health Inspection Service. Confirmation included both morphological and molecular analysis.
This detection is especially concerning due to the aggressive nature of this parasitic weed and its potential to spread rapidly if left unmanaged. Sunflower broomrape poses a serious threat to commercial sunflower production and could cause significant impacts to growers, processors, exporters and the agricultural economy if not swiftly contained.
The WSDA Pest Program is working closely with USDA and local stakeholders to investigate the source, assess the extent of the infestation, and respond to protect North American agriculture.
Native to Eurasia, Orobanche cumana is a quarantine pest in many countries due to its devastating impact on sunflower production. Although O. cumana attaches to the host plants’ roots, it does produce distinctive above-ground, leafless flower stalks. A single plant can produce hundreds of thousands of microscopic seeds that remain viable in the soil for decades, making eradication difficult once established, according to a Department of Agriculture pest alert.
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Public’s help needed
Now we rely on the public, landowners, and gardeners to help us look for and eradicate sunflower broomrape.
Sunflower broomrape attaches to a host plant’s roots, forming pale, leafless shoots that draw nutrients and weaken the plant. The invasive species was recently detected near Yakima and should be reported if found.
Photo courtesy of Yakima County Noxious Weed Board
In fall 2025, the Yakima County Noxious Weed Board and Washington State Department of Agriculture teamed up to survey a one mile radius of the site where Orobanche cumana was found. No additional sites were found. However, the plant can be easily overlooked as a cool wildflower or an interesting plant.
Orobanche seeds rely on a chemical signal from the host plant in the soil to start the germination process. The plant then attaches to the root of the host plant, forms a tubercle and takes all needed nutrients and water from the host to develop. This process takes a couple of weeks underground. It then emerges as an asparagus like stem, growing and flowering within a couple weeks within the root zone of the host. Lacking chlorophyll, the plants can survive in full shade and are very inconspicuous.
O. cumana can grow up to 2 or more feet tall in sun or shade. Pale stems lack leaves and produce tubular flowers with bluish purple tips. Each flower forms a pod like a snapdragon seed pod, containing thousands of fine dust-like seeds. Seeds are viable for several decades in the soil and wait for a host to signal germination.
Here’s what to do if you suspect you have broomrape:
• Take pictures, especially stem and flower close-ups.
• Providing a crop history and seed sources are valuable.
• Do not collect samples initially because of possible seed spread.
• Contact the Yakima County Noxious Weed Board at 509-574-2180 or the WSDA at 1-800-443-6684.
WSDA or weed board staff members will collect the plants to minimize potential spread. Treatment is determined by location with the landowner and WSDA.
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