Biological control of russian thistle
Russian thistle (Salsolu iberica Sennen and Pau), a plant native to Eurasia, has become a widespread weed in California and other western states. In these areas it serves as a favored alternate host plant for the beet leafhopper, Circlulifer tenellus (Baker), vector of the destructive “curly top” virus of such crops as sugar beets, tomatoes, and melons. The plant also harbors a variety of other insect pests such as lygus and stink bugs. These large, bushy “tumbleweeds” are common sights on neglected or abandoned croplands, vacant residential and industrial lands, and highway and railroad right of ways. The plants fracture at the base at maturity and scatter seeds as they are blown about by the wind. Tumbleweeds fill irrigation and drainage canals, pile up against fence and buildings, fill backyards and swimming pools, and startle motorists who encounter them while driving. Unsightly accumulations of the dead, dry plants are not only difficult to remove, but also create fire hazards and traps for other windblown debris.