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United States Department of Agriculture

Agricultural Research Service

Research Project: Biological Control of Invasive Terrestrial and Riparian Weeds in the Far Western U.S. Region, with Emphasis on Thistles, Brooms and Cape-ivy

Location: Exotic and Invasive Weeds Research

Title: Open field experiment to assess the host specificity of Lixus cardui (Coleoptera: Curculionidae), a potential candidate for biological control of Onopordum acanthium (Asteraceae)

item Harizanova, Vili -
item Stoeva, Atanaska -
item Cristofaro, Massimo -
item Paolini, Alessandra -
item Lecce, Franc -
item Di Cristina, Francesca -
item DE Biase, Alessio -

Submitted to: International Symposium on Biological Control of Weeds
Publication Type: Proceedings
Publication Acceptance Date: August 14, 2012
Publication Date: N/A

Technical Abstract: Scotch thistle Onopordum acanthium (Asteraceae) is native to Europe and Asia and has been accidentally introduced to temperate climates elsewhere, including North America and Australia. In the USA, the weed is most problematic in the semi-arid parts of the Northwest, California and Nevada. Lixus cardui is a weevil that lays its eggs in the flowering stem of Scotch thistle in cavities chewed by ovipositing females. The larvae burrow, feed and pupate within the stem. An open field experiment, to evaluate the host specificity of the weevil, was conducted on a small experimental plot at the Agricultural university of Plovdiv, Bulgaria. In 2010 nine plant species, belonging to the family Asteraceae, were tested: O. acanthium, Cirsium arvense, Arctium lappa, Carduus acanthoides, Carthamus tinctorius and Centaurea cyanus, Cynara scolymus, Silybum marianum, and Helianthus annuus. In 2011 Ci. arvense was replaced by three species native to North America: Cirsium loncholepis, Cirsium rhothophilum, and Cirsium hydrophilum. Each year adult L. cardui were collected in May and June in the area around Plovdiv and were released in the experimental field, one or two on each plant. At the end of August the mature plants were dug out, and the stems were dissected and examined for larvae, pupae or adults of L. cardui. The results of dissections showed that all bolting plants of O. acanthium and A. lappa were damaged by the weevil, while its presence was never observed in any other test species. Specimens of L. cardui from these experiments are currently undergoing genetic and morphological studies to determine if the insects from A. lappa are different from those from O. acanthium.

Last Modified: 7/25/2014
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