Biological control of yellow toadflax (Linaria vulgaris) by Eteobalea serratella in peppermint (Mentha piperita)

Yellow toadflax is an introduced ornamental perennial that has become a ser ious weed in Wisconsin peppermint production. Glyphosate is the only labele d herbicide that controls yellow toadflax in peppermint. Other control stra tegies, either mechanical or cultural, have little effect on the weed in so lid stands of peppermint. Previous research has suggested chat the root min ing moth Eteobalea serratella Tr. (Lepidoptera: Cosmopterigidae) may provid e effective biological control of yellow toadflax. Therefore, experiments w ere conducted to determine the host specificity of E. serratella and to qua ntify E, serratella root mining of yellow toadflax. In larval and adult no- choice tests, E. serratella attacked only yellow toadflax. Other plant spec ies collected from E. serratella's natural range were not attacked, neither those closely related to yellow toadflax in the family Scrophulariaceae, n or those closely related to peppermint in the family Labiatae. Root mining by E. serratella reduced root biomass an average of 20% compared to nontrea ted plants, Peppermint competition alone or in conjunction with root mining by E. serratella reduced root biomass 52 and 65%, respectively, compared t o nontreated plants under noncompetitive conditions. E. serratella is host specific for yellow toadflax and demonstrates potential as a biological con trol agent by contributing to the reduced competitive ability of yellow toa dflax in peppermint.