It is critical that the appropriate stem-boring weevil be utilized on the specific species of toadflax you are trying to control. Presently, the only reliable way to distinguish Mecinus janthinus(for yellow toadfax) and M. janthiniformis (for Dalmatian toadflax) appears to be the host plant on which they were collected. Please discuss with your supplier to ensure the agents you receive were collected from the same species of toadflax for which you plan to release them. Morphological differences of the weevils are very subtle and may not be reliable.
Biological Control Agents
The stem-mining weevil Mecinus janthinus was released in the US and Canada as a biological control agent of Dalmatian and yellow toadflax. Recent research has shown that rather than a single Mecinus species, there are two host-specific Mecinus weevils that utilize weedy toadflaxes. These are:
• Mecinus janthinus, which utilizes yellow toadflax, and,
• Mecinus janthiniformis, which utilizes Dalmatian toadflax.
Both weevils have apparently been released and established in the U.S. Choosing the appropriate host-specific weevil should increase the efficacy of biological control of both Dalmatian and yellow toadflax.
Dalmatian and Yellow Toadflax (Linariadalmatica and L. vulgaris)Identification:
Dalmatian and yellow (or common) toadflax are members of the Plantaginaceae (plantain) family, and are easily recognized by their snapdragon-like yellow flowers (right) with a single long spur. Flowers can bloom from early summer until killing frost.
• Dalmatian toadflax ranges in height from 15-60 inches with broad, fleshy and heart-shaped leaves which clasp the stem.
• Yellow toadflax is shorter, from 7-32 Inches tall with leaves that are long, linear and noticeably less succulent
Visit the weed identification pages for yellow toadflax and dalmatian toadflax for more information on these two weeds.
Dalmatian toadflax is on the left and Yellow toadflax on the right
Please contact your local county weed coordinator or Gary D. Adams, State Plant Health Director at USDA, APHIS, PPQ if you have questions.