Suitability of two root-mining weevils for the biological control of scentless chamomile, Tripleurospermum perforatum, with special regard to potential non-target effects.
The biology and host range of the two root-mining weevils Diplapion confluens Kirby and Coryssomerus capucinus (Beck), two potential agents for the biological control of scentless chamomile Tripleurospermum perforatum (Mérat) Laínz, were studied in the field in southern Germany and eastern Austria, and in a common garden and under laboratory conditions in Delémont, Switzerland from 1993 to 1999. Both weevils were univoltine, and females started to lay eggs in early spring. Diplapion confluens had three and C. capucinus five instars. Larvae of both species were found in the field from mid-April until the end of July; later instars preferentially fed in the vascular cylinder of the shoot base, root crown or root. Although larvae of both species occupy the same temporal and spatial niche within their host plants, they occurred at all investigated field sites together, and showed a similar distribution within sites. No negative or positive interspecific association was detected. Host-specificity tests including no-choice, single-choice, and multiple-choice tests under confined conditions, as well as tests under field conditions with natural and augmented insect densities revealed that both herbivores were specific to plant species in the tribe Anthemideae. However, their development to mature larva or adult on several cultivated plants, as well as on one plant species native to North America, rendered them unsuitable for field release in North America. It was concluded that to investigate non-target effects reliably, host-specificity tests with biological control agents should be carried out under a variety of conditions, particularly with augmented insect densities, as are expected to occur naturally after release.
Hinz
H L
HL
CABI Bioscience Centre Switzerland, Rue des Grillons 1, CH-2800 Delémont, Switzerland. h.hinz@cabi-bioscience.ch
Müller-Schärer
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H
D000818:Animals; D020843:Chamomile / Q000469:parasitology*; D001517:Coleoptera / Q000254:growth & development / Q000502:physiology*; D005260:Female; D008018:Life Cycle Stages; D010572:Pest Control, Biological; D010946:Plants, Medicinal