Not known to transmit any human or animal pathogens.

Not known to vector any plant pathogens or other associated organisms.

This plant is not known to be a vector and it is not vectored by any organism.

Sunflower broomrape emerges from the soil as pale yellow to purple leafless unbranched flowering stems, somewhat resembling asparagus near the base of the hosts. The stems typically grow to about 16 to 24 in tall, have scales instead of leaves, and lack chlorophyll. Their flowers are distinctly bilabiate (two-lipped), featuring two upper lobes and three lower lobes. Seeds are tiny and cannot be easily detected with the naked eye in the field. See the datasheet for images.

Stunting, wilting, yellowing, or plant death. See datasheet for images.

Surveys should begin about one month after sunflower planting and should be repeated one to two weeks later. Broomrape stems should still be detectable later in the growing season, but will not have flowers.

Survey for sunflower broomrape in sunflower (Helianthus annuus L.) fields. 

Sunflower broomrape may be patchy within a field so surveyors should focus on areas of the field where sunflower plants are stunted, wilted, or have yellow leaves. Since sunflower broomrape is small and could be obscured by the host canopy, surveyors should first look for symptoms on sunflower and then for broomrape stems at the base of the host. If surveyors do not find pale yellow to purple stems at the base of symptomatic plants, a follow up survey should be conducted about 1 to 2 weeks later to re-examine the area for broomrape stems. Since sunflower symptoms are not specific to broomrape infection and the weed starts growing below-ground, timing surveys to coincide with above-ground broomrape stems is ideal. In the absence of symptomatic sunflowers, surveyors should walk the perimeter and interior of the field looking for broomrape stems at the base of sunflower plants.

To prevent spreading dust-like seeds within and between fields, collect samples carefully in place and double??'bag them immediately. Collect the entire above??'ground stem, prioritizing stems with flowers. Clean hands, clothing, equipment, tools, and footwear between survey locations to avoid inadvertently moving seeds. 

For morphological identification, take photos of the plants, including the population, entire plant, and close-ups of the flowers. Collect mature stems with open flowers and press them between moisture-absorbing papers, such as newspapers or blotting sheets, making sure the specimens are not crowded or overlapped. If mature fruits are present, handle them carefully to prevent seed spillage, as they can detach easily. Collect stems with fruits in ziplock bags, seal and double-bag them immediately. Collect pressed specimens and photos of the host plants to confirm host ID.

1. Collins, L. T., A. E. L. Colwell, and Yatskievych, G. 2024. Orobanche. Flora of North America. 
2. Pujadas-Salva, A.J. and Velasco, L. 2000. Comparative studies on Orobanche cernua L. and O. cumana Wallr. (Orobanchaceae) in the Iberian Peninsula. Botanical Journal of the Linnean Society, 134(4): 513-527.
3. Domina, G. A. 2026. Synopsis and Nomenclatural Review of Orobanche (Orobanchaceae). Brittonia 78, 47-93.

The genus Orobanche includes about 200 species of parasitic plants worldwide, with about 19 species occurring in North America. There are many parasitic plant species in the United States referred to as broomrape. Sunflower broomrape may be mistaken for other Orobanche/Phelipanche species, but only a few infect sunflower. Phelipanche aegyptiaca (syn. Orobanche aegyptiaca), Egyptian broomrape, has been detected on sunflower in California, but is not known to occur elsewhere in the United States. Egyptian broomrape has a branched flowering stem while sunflower broomrape has an unbranched stem. Orobanche ludoviciana, Louisiana broomrape, is native to the United States and was reported parasitizing sunflower only once, in Nebraska in 2014. Compared to sunflower broomrape, Louisiana broomrape has a shorter stem with pinkish flowers. Several other Orobanche/Phelipanche species parasitize members of the Asteraceae, but none have been documented using sunflower as a natural host to date.