Feeding Preference for and Impact on an Invasive Weed (Crepis tectorum) by a Native, Generalist Insect Herbivore, Melanoplus borealis (Orthoptera: Acrididae)
Fielding, Dennis J. | Conn, Jeffery S.
Crepis tectorum L., narrow leaf hawksbeard, first was collected in Alaska in 1974 and by 2004 was a common weed in agricultural fields. Introduction and establishment of a new plant species in a region represents a potential new resource for herbivores, as well as a new competitor for plant species already present. Objectives of this study were to determine the preference for C. tectorum, relative to other common plant species, by Melanoplus borealis (Fieber), a generalist herbivore grasshopper common in Alaska, and to determine the potential impact of grasshoppers on this weed. In choice tests, M. borealis preferred C. tectorum over two native forbs, and a grass species, but dandelion, Taraxacum officinale G. H. Weber ex Wiggers, was preferred over C. tectorum. In field cages, in each of 3 yr, grasshoppers reduced biomass of mature plants, flowers, and seedlings of C. tectorum, but not other forbs. We conclude that this weed is a readily accepted new food resource for generalist-feeding grasshoppers, and although grasshoppers could potentially limit seed production of C. tectorum, generally grasshopper densities are not high enough to have significant impact on the weed populations.Show more [+] Less [-]