Orobanche cumana, commonly called Sunflower Broomrape, is a devastating parasitic weed that can cause yield losses to sunflower. The first report of Orobanche cumana in the Western hemisphere was in Bolivia in 2024. The first report in North America occurred in Yakima, WA in 2025, which was followed immediately by eradication efforts. At the time of this writing, Orobanche cumana has not been found elsewhere in North America and has never been observed in any major U.S. sunflower production area (commercial or seed). This Extension Alert is designed to bring awareness and information to the North American sunflower communities in an effort to prevent future introduction and/or establishment of this parasitic weed on the continent.

Broomrapes from the genus Orobanche, now reclassified to include the genera Aphyllon and Phelipanche, are noxious, holoparasitic weeds (entirely dependent on their host plants for nutrition). Orobanche plants have no chlorophyll and cannot manufacture their own nutrients. Consequently, all water and nutrients are taken from the roots of the parasitized plant, resulting in high yield loss to the host. Due to the potential yield-threat to domestic plants, all non-native Orobanche species (including O. cumana) are on the U.S. Federal List of Noxious Weeds, making transport of their seeds illegal.

Orobanche cumana is a species that specifically parasitizes sunflowers, and is thought to have originated in Russia and Eastern Europe. Spread of O. cumana followed expansion of sunflower production across Ukraine, Moldova, Romania, Bulgaria, and Hungary. It is now widespread in major sunflower-growing areas, including Spain, France, Italy, Romania, Hungary, Bulgaria, and Ukraine. Yield losses in severely affected fields in Europe and Russia have reached 50% or more. Orobanche cumana is also present in Israel, China, and Tunisia, but was not found in the Western hemisphere until 2024.

Orobanche cumana is commonly first observed as a plant (or cluster of plants) growing from the roots of a sunflower plant (Figure 1). A single parasitized sunflower plant may have one to several dozen Orobanche plants attached to the root system. Young Orobanche plants (prior to flowering) often appear similar to asparagus.

Figure 1. Orobanche cumana stems emerging at the base of sunflower plants (courtesy Tatiana Antonova).

Each Orobanche cumana plant consists of a single, pale yellow- white to light-brown stem, reaching 16-25 inches (40-60 cm) in height. The stem has small, white to pale blue flowers, slightly resembling a snapdragon (Figure 2). The corollas of the flowers are purple-tinted and curve downward.

Figure 2. Close-up of a cluster of Orobanche flowers (Courtesy, Yakima County Noxious Weed Board).

Orobanche plants produce multiple flowers, with up to 100 flowers on large plants. Each flower produces a capsule containing up to 1,000 minute seeds roughly measuring 1/100 – 1/64 inch x 1/250 – 1/125 inch (0.25 - 0.4 mm X 0.1 - 0.2 mm) that resemble finely ground pepper. Seeds are very lightweight, with 2-3 million seeds weighing just 1 ounce (approx. 28 grams). The dust-like seeds are very difficult to see and are easily dispersed, increasing the risk of inadvertent spread. Seeds remain viable in soil for up to two decades, creating a seedbank that may number in the millions from a single parasitized sunflower.

While Orobanche cumana is the topic of this alert, multiple Orobanche species exist on many different hosts, including those native to North America. Orobanche species may be distinguished by stem size and the mode of branching, as well as flower color, size, and shape. However, DNA testing may be needed for precise species confirmation in some cases.

Broomrape plants are annuals, germinating from seeds each year. Orobanche cumana has a narrow host range that includes cultivated, ornamental, volunteer and wild sunflower. Seeds are stimulated to germinate in the presence of chemical root exudates of potential hosts, and form germ tubes that penetrate sunflower roots. Inside the sunflower root, specialized structures (haustoria) are formed that extract nutrients from the parasitized sunflower plant. Tubercles, initially appearing as small nodules and later enlarging to shoots, develop on the parasitized root surface (Figure 3). Tubercles develop into Orobanche stems that emerge approximately 35 days after forming. Flowers of Orobanche produce seed quickly, approximately 18-20 days after emergence. Seeds are easily spread by wind, water, livestock and animals. Humans can inadvertently spread seed, particularly in contaminated soil on machinery, vehicles, boots, etc.

Figure 3. Multiple Orobanche plants attached to one sunflower root system. Numerous tubercles (and the shoots of future stems that develop from them), at various stages of development, are attached to the sunflower roots (Tatiana Antonova, VNIIMK).

Although it is unlikely you will ever see Orobanche cumana, BOLO (be on the look-out) whenever you see sunflowers. Early identification and eradication are critical to prevent of O. cumana in North America. If you suspect Orobanche, we recommend:

1. DO NOT collect plants, as seeds can easily be inadvertently spread.
2. Take pictures, with emphasis on close-up images of the flowers.
3. Collect information on the source of the sunflower seed and field cropping history (if possible)
4. Record the specific location of the plants so they can be found for future identification.
5. Contact an expert. We recommend sending photos and information to a university diagnostic plant disease laboratory, an Extension plant pathologist, or the state department of agriculture.
6. Take reasonable steps to minimize the chance of inadvertent spread, should the plant be confirmed as Orobanche cumana. This could include careful cleaning of hands/clothing if you touch plants, restrict access to the area if you own the property, etc.

Although not needed in North America, management tools for Orobanche cumana are available in other sunflower producing regions. Using as many management tools as possible in an Integrated Pest Management (IPM) approach will achieve the best results. Herbicide application (such as HRAC group 2) in tolerant sunflowers have may provide efficacy against Orobanche cumana. Genetic resistance is available and may be effective. However, the parasitic weed has developed multiple races, so selection of cultivars with resistance genes effective in that field are important for Broomrape management. Further, rotation of cultivars with different effective genes helps prevent the development of new races. Crop rotation is beneficial as Orobanche cumana has a narrow host range, however, seeds may last for many years. Sanitation measures (cleaning equipment, harvest infected field last) help reduce spread.

Figure 1. Orobanche cumana stems emerging at the base of sunflower plants (courtesy Tatiana Antonova).
Figure 2. Close-up of a cluster of Orobanche flowers (Courtesy, Yakima County Noxious Weed Board).
Figure 3. Multiple Orobanche plants attached to one sunflower root system. Numerous tubercles (and the shoots of future stems that develop from them), at various stages of development, are attached to the sunflower roots (Tatiana Antonova, VNIIMK).

Sunflower broomrape (Orobanche cumana), a serious parasitic weed identified for the first time in the U. S. powerpoint: https://www.sunflowernsa.com/uploads/179/15_revised_Charles.Block_Orobanche.cumana_2026.Forum.pdf

Research Paper: https://www.sunflowernsa.com/uploads/research/1468/NSAResearchsummaryonOrobanchecumana-2026.pdf

News Release: WSDA seeks help from sunflower growers after first North American detection of sunflower broomrape confirmed in Yakima. https://agr.wa.gov/about-wsda/news-and-media-relations/news-releases?article=44833.

This work is supported by the Crop Protection and Pest Management Program, project award no. 2022-70006-38001, from the U.S. Department of Agriculture’s National Institute of Food and Agriculture. We thank the North Central IPM Center and the National Sunflower Association for their support. We thank Dr. Tatiana Antonova, at VNIIMK, All Russia Research Institute of Oil Crops, Krasnodar, Russia, for her guidance and expertise in the preparation of this information. We thank the personnel of the Washington Department of Agriculture for their work in confirming the identity of Orobanche cumana and the Yakima County Noxious Weed Board for their prompt identification, eradication and monitoring efforts of the 2025 WA introduction site. We also thank all the members of the sunflower community and sunflower enthusiasts in their vigilance protecting sunflower.

This publication is based in part, and reproduced from, ‘Block, C., Gulya, T., Antonova, T., Harveson, R., Ryley, M., Thompson, S. and Markell, S. 2026. Orobanche cumana (Sunflower Broomrape): National Alert. NDSU Extension publication PPXXXX (4 pages).’