The seed-feeding weevil Mogulones borraginis has been recommended for release in North America to help control the invasive noxious weed houndstongue, based on a petition submitted by Centre for Agriculture and Biosciences International (CABI) scientists in collaboration with professor Mark Schwarzländer (University of Idaho) and Rachel Winston (MIA Consulting).

The recommendation by the U.S. Department of Agriculture (USDA) Technical Advisory Group (TAG) signals a key accomplishment in the process of getting M. borraginis released in the field as a classical biological control agent against houndstongue (Cynoglossum officinale), a rangeland weed in the western USA and adjacent Canadian provinces.

Houndstongue has become a significant problem in pastures, grasslands and open range, where it poisons animals that ingest it and hinders the establishment of desired forage species.

In a next step, USDA's Animal and Plant Health Inspection Service (APHIS) will prepare a biological assessment, a federal document required for consultations with the U.S. Fish & Wildlife Service. Once the weevil successfully passes this step, the petition still needs to go through consultations with tribal nations and U.S. states and public commenting periods before a release permit can be issued by APHIS.

In the last few years, CABI’s Swiss center in Delémont has maintained a rearing colony of the weevil, which is very rare in its native range in Europe. Fortunately, rearing is relatively easy, and so CABI was able to send hundreds of M. borraginis to a quarantine laboratory at the University of Idaho, led by Schwarzländer, to conduct research on the chemical ecology of the weevil affirming its environmental safety.

Dr. Hariet Hinz, regional director and head of the Weed Biological Control Programme at CABI in Switzerland, said, "The recommendation from TAG is very exciting as it represents significant progress in the long but necessary process of investigating the suitability of M. borraginis as a safe biological control agent, and is a major milestone in actually getting it released into the field, where it can take effect against the invasive weed.

"We hope the release can take place within the next two years. In the meantime, we are maintaining colonies of the weevil at CABI and in quarantine in the USA, so that we will be ready to release it when all the necessary checks and approvals have been done and granted."

A sibling species, the root-mining weevil Mogulones crucifer, was released in Canada in 1997 and is showing impressive success in reducing houndstongue populations to benign. However, concerns about its host specificity have thus far prevented its release in the USA, where many more native species in the same plant family as houndstongue (Boraginaceae) exist. Consequently, CABI and collaborators have been working to find other potential agents such as M. borraginis.

Additional information

Learn more about CABI’s work to find a biological control for houndstongue in the USA from the project page.

You can also discover more about work on M. borraginis for houndstongue and other biological controls for other weeds in the "Weed Biological Control Progress Report 2020" from CABI in Switzerland.