Dalmatian toadflax, a member of the snapdragon family, is easily recognized its bright yellow flowers. Native to the Mediterranean region it was introduced into the U.S. in the mid-1800's. Dalmatian toadflax is more adapted to the drier areas of North Dakota and is a relatively poor competitor with grass species. But once established the weed can become extremely invasive.
Dalmatian toadflax has an extensive creeping rhizomatous root system that spreads like Leafy spurge, extending up to 10 feet and giving rise to daughter plants every few inches. It flowers from late June through August and single plants can produce more than 500,000 seeds that are dispersed by wind, rain, wildlife, and movement of forage and livestock. Seed dispersal begins a few weeks after flowering and continues into winter.
Control on non-crop lands:
Prevention is the best method to keep toadflax from invading pasture, rangeland and wild lands. Herbicides are effective if used repeatedly and at high rates.
Chemical: Tordon (picloram), Plateau (imazapic) and Telar (chlorsulfuron) will control Dalmatian toadflax when applied at maximum use rates during flowering or late fall.
Cultural: Long term use of proper stocking rates on pastures and rangelands to maintain competitive forages species has helped reduce the spread of toadflax. Burning is not effective as soil temperatures do not get high enough to kill the roots.
Biological: The stem-boring weevil Mecinus janthinus has been successful and can reduce Dalmatian toadflax stands relatively quickly.