Disturbance, Season of Recruitment, Competition and Herbivory Effects on Ragwort Populations

Data from a field experiment examining the effects of season of disturbance (tilled soil in Fall 1986, Spring 1987), 3 levels of interspecific plant competition (other vegetation Removed, Clipped, or Unaltered) and exposure to two biological control agents (ragwort flea beetle, cinnabar moth) on tansy ragwort (Senecio jacobaea, syn. Jacobaea vulgaris) populations at Cascade Head Scenic Research Area on the Oregon coast, from 1986-09-05 through July 1990. Data on ragwort populations in experimental subplots (0.0625 m2) and plots (0.25 m2) includes: 1) julian day (day of year) of emergence, first incidence of herbivory, and death; 2) number of flowering plants and capitula; 3) number of new ragwort juveniles established in 1989; 4) percent cover of ragwort, other plant species, litter and bare ground; and 5) dry biomass of ragwort.