Weed Seed: Cuscuta spp. (Dodder)

Family

Convolvulaceae

Common name

Dodder

Regulation

Prohibited Noxious, Class 1 in the Canadian Weed Seeds Order, 2016 under the Seeds Act. All imported and domestic seed must be free of Prohibited Noxious weed seeds.

Listed on the List of Pests Regulated by Canada established under the Plant Protection Act. (Exception of: Cuscuta cephalanthi, C. coryli, C. gronovii, C. megalocarpa, C. pentagona, C. polygonorum and C. salina).

Distribution

Canadian: The genus includes 12 species found in Canada, distributed across all provinces except NT, NU and YT (Brouillet et al. 2016^Footnote 1).

Worldwide: The genus contains 194 species and is nearly cosmopolitan with the majority of species (approximately 75%) native to North and South America, and a small number (15-20 spp.) distributed worldwide as agricultural and horticultural pests (Costea et al. 2015^Footnote 2).

Duration of life cycle

Annual

Seed or fruit type

Seed

Identification features

Size

Seed diameter commonly is 1.0 - 1.5 mm, e.g. C. campestris, C. chinensis and C. epithymum; there are also some species that have larger size (e.g. C. lupuliform is 3.0 mm)

Shape

Seeds may be ovate, globose, or trigonous; may be compressed on one or two sides; radicle may protrude past the hilum

Surface texture

Surface of seeds is finely to coarsely rough, granular, pitted, reticulate or scurfy

Colour

Seed is light grey, yellowish, reddish or dark brown

Other features

Scar area round, in the centre the seed's hilum appears as a raised line, point or slit
Fruit is a capsule containing up to 4 seeds
Embryo coiled, endosperm hard and clear

Habitat and crop association

Dodders occupy a wide variety of habitats in temperate and tropical regions, including desert and riparian areas, littoral zones, high mountains, grasslands, forests, and saline and disturbed habitats. Like other parasitic plants, they are often keystone species in their ecosystems (Costea et al. 2015^Footnote 2).

General information

Many dodder species are generalists, attacking a wide range of host species from different plant families, while others are more host-specific. Economically important species are especially problematic in legumes (e.g., alfalfa, clovers) and flax. Dodder species do not typically attack grasses or sedges (Poaceae, Cyperaceae) (Costea and Tardif 2006^Footnote 3).

Similar species

Inert material

Rounded pieces of sap from stems removed during processing can appear like dodder seeds, but they lack the hilum of dodder and are usually translucent.
Inert stone cells from Solanum spp. may have a similar round shape, rough surface, size and yellow colour as dodder, but they lack the hilum of dodder.