TRANSMISSION OF PUCCINIA-CARDUORUM BY THE MUSK THISTLE HERBIVORES, CASSIDA-RUBIGINOSA (COLEOPTERA, CHRYSOMELIDAE), TRICHOSIROCALUS-HORRIDUSAND RHINOCYLLUS-CONICUS (COLEOPTERA, CURCULIONIDAE)

An autoecious rust fungus, Puccinia carduorum Jacky (Uredinales), impo rted from Turkey has been introduced for the biological control of mus k thistle in Virginia. Studies were conducted to determine if this rus t can be transmitted by the three thistle herbivores, Cassida rubigino sa Muller (Coleoptera: Chrysomelidae), Trichosirocalus horridus (Panze r), and Rhinocyllus conicus Froelich (Coleoptera: Curculionidae). Fift y adults of each species were introduced to diseased plants and subseq uently transferred to healthy test plants. Fifty adults introduced on and transferred to rust-free plants served as control. Spore dispersal by adults of the three coleopteran species was confirmed. Under green house conditions, pustules developed within two weeks on some test pla nts where spore-carrying insects were introduced. Most of the uredinio spores were observed on setae of legs of all adults.