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Title: Insectary testing refutes host-herbivore relationship between Fragaria spp. and Abia sericea, a candidate for biological control of Dipsacus spp.

item Rector, Brian

Submitted to: International Symposium on Biological Control of Weeds
Publication Type: Proceedings
Publication Acceptance Date: 1/22/2008
Publication Date: 12/31/2008
Citation: Rector, B.G., Harizanova, V., Stoeva, A. 2008. Insectary testing refutes host-herbivore relationship between Fragaria spp. and Abia sericea, a candidate for biological control of Dipsacus spp.. International Symposium on Biological Control of Weeds.

Interpretive Summary: Abia sericea is a European sawfly that is a candidate for biological control of invasive teasels, a group of Eurasian weeds that are becoming problematic in the US. Larvae of A. sericea feed on teasel plants and it is hoped that if they were introduced into the US, they would reduce invasive teasel populations and stop or reverse the spread of this weed. Reports in the scientific literature indicate that A. sericea larvae also eat wild strawberry plants and perhaps also cultivated strawberry plants, which would preclude their use as biological control agents. Tests were conducted to determine whether reports of A. sericea feeding on strawberry species were valid. A variety of tests were conducted using both larval and adult sawflies on three strawberry species, including cultivated strawberry. There was no indication whatsoever that larvae of A. sericea would feed on either wild or cultivated strawberries or that female A. sericea adults would lay their eggs on them. In conclusion, records in the literature denoting a herbivore-host connection between A. sericea and strawberries are erroneous.

Technical Abstract: For more than a century, Fragaria L. (Rosaceae), the genus of cultivated and wild strawberries, has been listed in the entomological literature as a food source for larvae of the European sawfly Abia sericea (L.) (Hymenoptera: Cimbicidae). This listing represents the only known host record from outside the closely related families Dipsacaceae and Caprifoliaceae for any European species in the genus Abia Leach. A variety of bioassays were employed to test the validity of this herbivore-host connection, including choice and no-choice, detached-leaf and live-plant, and larval-feeding and adult-oviposition bioassays. Abia sericea populations collected from four locations in Bulgaria were tested on three species of Fragaria, including the two wild species implicated in the scientific literature as hosts of A. sericea (F. vesca L. and F. viridis Duchesne), and the cultivated strawberry (F. x ananassa Duchesne). The results indicated a lack of suitability for any of the Fragaria spp. as hosts of A. sericea. There was no feeding or evidence of feeding attempts by any of the 47 A. sericea larvae involved in the bioassays, including 35 that starved to death in no-choice bioassays on Fragaria, whereas cohorts of these larvae fed and developed normally on Dipsacus laciniatus. Abia sericea females laid 90 eggs on D. laciniatus plants while exhibiting an oviposition-associated behavior when in contact with these plants, whereas they lad no eggs on strawberry plants and exhibited no such behavior. Additional biological observations on A. sericea are reported.