Houndstongue, Cynoglossum officinale L. Boraginaceae, is a herbaceous, monocarpic, short-lived perennial weed introduced from Europe. It invades rangelands in the western United States and British Columbia and is toxic to livestock. A biological control project was initiated in 1988 to control houndstongue. The root-mining flea beetle, Longitarsus quadriguttatus Pont, is the second agent released for control in Canada. Previous host-specificity investigations with 49 European and 5 North American test plant species demonstrated that larval development of the flea beetle is largely limited to plant species within the tribe Cynoglosseae. However, previous investigations included only 2 species within 1 native North American Boraginaceae genus. We conducted a set-design open-field oviposition and larval development test both with (choice) and without (no-choice) the presence of houndstongue. The test plant species included 3 native North American Boraginaceae species, 2 European species and 1 cosmopolitan species. The results between choice and no-choice open-field plots differed significantly. In the no-choice plots an average of ten L. quadriguttatus larvae were found in roots of the cosmopolitan species Lappula deflexa and less than one larva per plant was found in the roots of the two European species and one North American species. In the choice open-field plots, houndstongue roots contained an average of 80 L. quadriguttatus larvae. In addition, an average of 1-5 larvae were found in L. deflexa, Echium vulgare, Lithospermum vulgare and Mertensia ciliata. The two native North American Cryptantha species remained free of attack. Differences in infestation rates between houndstongue and test plant species were not significant because of the variation of data.
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA