Biology and Biological Control of Exotic True Thistles

“Thistle” is an old English name for a large variety of weedy, prickly plants that grow throughout the world. The most notable characteristics of thistles are the prickly stems and leaves and the bracts around the flower head. While many different plants have “thistle” in their common name, only certain plant species fit the taxonomic requirements of being considered “true thistles.” True thistle species fall within the family Asteraceae, the tribe Cardueae, and the subtribe Carduinae. Examples of plants that are not true thistles include yellow starthistle (subtribe Centaureinae), sow thistle (subtribe Sonchinae), and Russian thistle (family Chenopodiaceae). Only true thistles in the subtribe Carduinae are discussed in this manual

Biology and Biological Control of Exotic True Thistles

“Thistle” is an old English name for a large variety of weedy, prickly plants that grow throughout the world. The most notable characteristics of thistles are the prickly stems and leaves and the bracts around the flower head. While many different plants have “thistle” in their common name, only certain plant species fit the taxonomic requirements of being considered “true thistles.” True thistle species fall within the family Asteraceae, the tribe Cardueae, and the subtribe Carduinae. Examples of plants that are not true thistles include yellow starthistle (subtribe Centaureinae), sow thistle (subtribe Sonchinae), and Russian thistle (family Chenopodiaceae). Only true thistles in the subtribe Carduinae are discussed in this manual

Biology and Biological Control of Leafy Surface

Leafy spurge (Euphorbia esula L.) is an exotic, deep-rooted, perennial weed native to Europe and Asia. It was first reported in the United States in Newbury, Massachusetts, in 1827, where it likely established from contaminated soil left from ship ballasts. This invasive weed quickly spread westward across North America, accelerated by multiple reintroductions from contaminated crop seed including oat (Avena fatua L.), smooth brome (Bromus inermis Leyss.) and alfalfa (Medicago sativa L.) brought by European settlers. Leafy spurge is now abundant on the northern Great Plains of the United States and the prairie provinces of Canada, where it often forms stands dense enough to displace native plants and restrict cattle grazing