Orobanche L. and Phelipanche Pomel
NOTE: The information on this page covers both noxious and non-noxious Orobanche and Phelipanche species (see below). All species of Orobanche and Phelipanche are regulated as plant pests under 7 CFR 330.
Note: This description is primarily based on the morphology of just 12 species (both noxious and non-noxious (see below)).
Fruit usually a loculicidal or septicidal capsule with numerous seeds. Seeds commonly narrowly to broadly wedge shaped, irregularly wedge shaped, or teardrop-shaped, also elliptic, obovate, or oblong; tiny, dustlike, 0.2–0.6 mm long, 0.1–0.5 mm wide and thick. Straw-colored, pale brown, reddish amber to black-brown; often shiny. Surface reticulations prominent, intermediate to large in size, often high-walled; walls thick, thin, coarse or moniliform; sometimes nearly transparent, sometimes wavy. Embryo very small to minute; endosperm present.
Surface reticulation features as viewed under SEM or fluorescence microscopy may be a way to differentiate species. The noxious and non-noxious Orobanche and Phelipanche species are not morphologically distinct groups. Orobanchaceae species are closely related to those in the Scrophulariaceae. Compare Orobanche and Phelipanche with very small seeds of other parasitic plants on the federal noxious weed list:
mostly north temperate and subtropical; Africa, Asia, Australia, New Zealand, Colombia, United States
thrives on poor soils
Orobanche and Phelipanche are annual or perennial root parasites lacking chlorophyll, rarely more than 1 m tall. Seeds germinate in response to host root exudates and the seedling must contact a host root immediately after germinating. Some species may produce flowers within a week of emergence from the soil. Orobanche and Phelipanche commonly parasitize Solanaceae and Fabaceae hosts such as tomato, pepper, bean, pea, sunflower, and tobacco, reducing crop yields or totally destroying the crop. Orobanche and Phelipanche are usually not specific to a single host; most species parasitize a range of hosts, although among Orobanche and Phelipanche species host ranges may differ.
The two genera together comprise ca. 150 species. Species of agronomic importance are P. aegyptiaca (Pers.) Pomel, P. ramosa (L.) Pomel, O. crenata Forssk., O. cernua Loefl., and O. minor Sm. Phelipanche ramosa and Orobanche minor occur in the U.S. and in much of the world; P. ramosa is particularly widespread and harmful. Orobanche hederae Duby and O. loricata Reichb. are weeds of minor importance native to Europe.
All Orobanche and Phelipanche are on the federal noxious weed list except the following, which are native to the U.S. or introduced and widespread (but note that all species of Orobanche and Phelipanche are regulated as plant pests and require a pest permit for importation or interstate movement):
Orobanche bulbosa (Gray) Becik, O. californica Schlecht & Cham., O. cooperi (Gray) Heller, O. corymbosa (Rydb.) Ferris, O. dugesii (S. Wats.) Munz, O. fasciculata Nutt., O. ludoviciana Nutt., O. multicaulis Brandeg., O. parishii (Jeps.) Heckard, O. pinarum Geyer ex Hook., O. uniflora L., O. valida Jeps., and O. vallicola (Jeps.) Heckard.
Phelipanche aegyptiaca A, seed; B, longitudinal section of seed showing embryo; C, transection of seed; fruit (far right); drawings by Lynda E. Chandler (seed, left) and Regina O. Hughes (fruit, right)
Orobanche cernua A, seed; B, longitudinal section of seed showing embryo; C, transection of seed; fruit (far right); drawings by Lynda E. Chandler (seed, left) and Regina O. Hughes (fruit, right)