Biology and biological control of dalmatian and yellow toadflax

Abstract

Dalmatian toadflax, Linaria dalmatica (L.) P. Mill. ssp. dalmatica (Fig. 1a), and yellow toadflax, Linaria vulgaris (L.) P. Mill. (Fig. 1b), are exotic [see Glossary] weeds of rangeland, forests and cropland. Although several species of weedy toadflax have been intentionally or accidentally introduced to North America, these two species are by far the most common and problematic for land managers. Both species are known to thrive particularly well in disturbed, open habitats, are most competitive, and can easily dominate native or desirable plant communities in areas characterized by dry summers. Both Dalmatian and yellow toadflax are taprooted, short-lived perennial forbs that propagate by seeds and shoots growing from vegetative root buds. Toadflaxes belong to the genus Linaria in the figwort family, Scrophulariaceae. Both of these highly competitive and invasive plants were introduced to North America from Eurasia during the 1800s as ornamental plants, and for use in fabric dye and folk remedies. Dalmatian toadflax is native to the region extending from central Europe to central Asia. Yellow toadflax originates from central Europe and the Mediterranean area. Their widespread distribution in North America is likely due to their use as ornamen- tal plants. Exotic toadflaxes continue to be sold commercially in the United States, advertised as “butter and eggs,” “wild snapdragon,” “Jacob’s ladder,” or “yellow toadflax,” although the sale of these two species is illegal in states where they are listed as noxious weeds.