HPIPM:Yellow toadflax

Taxonomy

Domain	Eukarya
Kingdom	Plantae
Phylum	Magnoliophyta
Class	Magnoliopsida
Superorder	Asteranae
Order	Lamiales
Family	Plantaginaceae
Genus	Linaria

Scientific Name

Linaria vulgaris

Common Name

yellow toadflax

Yellow toadflax (Linaria vulgaris)

Author: George Beck, Colorado State University Cooperative Extension

Adapted from the Colorado State University Extension Natural Resources Fact Sheet "Biology and Management of the Toadflaxes"

Identification and Life Cycle

Yellow toadflax (Linaria vulgaris) is a creeping perennial in the figwort family (Scrophulariaceae). Flowers resemble those of cultivated snapdragon; each has a spur extending below from the lower lip of the corolla. They are about 1 inch long, bright yellow with a bearded, orange throat and occur in terminal, somewhat elongated clusters with the youngest flowers at the tip. The fruit is a brown, globe-shaped, two-celled capsule, 1/4 of an inch in diameter containing many seeds. Seeds are small, round, rough, flattened, with a papery, notched circular wing, dark brown, and about 1/12 of an inch in diameter. Stems are smooth, erect, leafy, often in clumps, and 1to 2 1/2 feet tall. Numerous pale green leaves are alternate, narrow, pointed at both ends, and 2 1/2 or more inches long. Yellow toadflax roots grow 3 feet deep or more with lateral roots that may extend several yards.

Habitats

Toadflax invasion is favored by disturbance, and it invades degraded areas such as roadsides, abandoned lots and fields, gravel pits, clearings, and overgrazed rangeland.

Impacts

Yellow toadflax is an aggressive invader and will displace desirable plant species. This species can also be poisonous to livestock if consumed in large quantities.

Biology and Ecology

Seeds of yellow toadflax germinate and emerge in early to mid-May depending on location and elevation. Seedling root development is slow and represents a life stage vulnerable to control attempts and plant competition. Disturbance promotes toadflax invasion and may be necessary for establishment to occur. However once established, yellow toadflax readily spread into adjacent non-disturbed areas. Much of this spread is by vegetative means, reflecting a vigorously growing root system. Yellow toadflax seedlings produce vegetative shoots from root buds two to three weeks after germination. Yellow toadflax begins to flower when shoots are from 16 to 24 inches tall but may not flower until fall under drought conditions. Yellow toadflax shoot phenology in any given patch may range from vegetative to flowering to seed set, depending on the time of season and environmental conditions (particularly moisture). This contributes to management difficulties.

Management Approaches

All toadflax species are very difficult to control, and management plans should integrate as many strategies as possible to increase potential for success. Assess the condition and composition of the existing plant community in an infested area, then determine the approximate composition of the desired plant community needed to achieve land management goals and objectives. Create a management plan that combines various control strategies to foster development of the desired plant community.

Biological Control

Several classical biological control agents are available to use against toadflaxes. However, the success of these agents remains largely unknown. A defoliating moth (Calophasia lunula), and two seed capsule feeding weevils (Rhinusa antirrhini and R. neta), a stem-boring weevil (Mecinus janthinus), and a root-boring moth (Eteobalea intermediella) have been released in the U.S. to control all toadflax species. These species may help to control shoots and seed production as well as decrease root vigor, but data are unavailable to document their effects.

Mechanical and Cultural Control

Cattle generally avoid grazing yellow toadflax. Mowing will not reduce infestations, but it may reduce seed production if done prior to flowering.

Chemical Control

Multiple treatments are typically needed as yellow toadflax readily recovers after a single application.

Consult herbicide labels for additional rate, application, and safety information. Additional herbicide information can be found at http://www.greenbook.net.

Due to constantly changing labels, laws and regulations, the sponsors of this web site assume no liability for the suggested use of any chemicals noted in the management section. Contact your local pest management personnel for current information on labeled pesticides that can be used for the intended plant disease, insect pest or weed.

References

For more information and images please visit IPM Bugwood. http://www.ipmimages.org/search/action.cfm?q=yellow%20toadflax