Not a dog, not a frog and not your friend
BY The Blaine County Bug Crew
This is part two of a two-part series on Dalmation toadflax and how we at The Blaine County Bug Crew control it with a bug called Mecinus janthiformus. Part one was published in the June 8 issue of The Weekly Sun.
The USDA – United States Department of Agriculture – spent many years searching overseas for Mecinus janthiformus, Dalmatian toadflax’s natural enemy.
This insect, also known as MEJA, spent many years in quarantine to make sure it would not harm any native plants or crops in the United States before it was unleashed on Dalmatian toadflax.
Adult MEJA are small, somewhat elongated bluish-black weevils that emerge from last year’s infested Dalmatian toadflax stems in April-May. Adult MEJA feed from June to mid-July before mating and laying eggs inside new shoots. The eggs typically hatch in 6-7 days. Larvae tunnel within the toadflax stem for 23-24 days, moving no more than 1.2 inches from where the egg was laid. Pupation occurs within the stem. Adult feeding on stems and leaves has limited impact on the plant. Larval mining impacts the plants by causing premature wilting of shoots and suppressing flower formation. MEJA winter as adults inside their pupation chamber. The effects of the weevil on the plant are reportedly enhanced under drought stress.
While we appreciate the public’s zeal in pulling up Dalmatian toadflax wherever they find it, sometimes you are pulling up Dalmatian toadflax that we have released bugs on and are monitoring. If you come upon an infestation of Dalmatian Toadflax with a pole in the middle and plastic whiskers nailed in the ground every 2 meters, you are in an active biological control site. The Howard Preserve in Bellevue is a good example of an area where well-intentioned individuals pull weeds indiscriminately and don’t realize the damage they are doing to the bugs and the data we provide to state and local agencies. The good news is that the Howard Preserve is full of Mecinus janthiformus!
If you know of an infestation of Dalmatian toadflax and think it would be a good site for biological control, give us a call at (208) 316-0355. Remember that the site needs to be free of major disturbances like spraying, grazing and cultivation for at least seven years.