Feeding preferences of the generalist insect herbivore, Melanoplus femurrubrum grasshopper, on invasive and native plants

The interaction between insect herbivores and plants is a mechanism, which may allow an exotic plant species to become invasive in the introduced range. Although there have been many studies on grasshopper feeding, only some of these examined feeding on native versus invasive plants; the question of whether grasshoppers as a generalist insect herbivore actively select native plants still remains unanswered.

I studied feeding of Melanoplus femurrubrum grasshoppers (Acrididae: Orthoptera) on two cultivars of a potentially invasive exotic chinese silver grass, Miscanthus sinensis (‘Zebrinus’ and ‘Gracillimus’) and two native grasses,  Andropogon gerardii (big bluestem) and Bouteloua curtipendula (sideoats grama). I performed no-choice and choice feeding experiments with juvenile plants and their leaves. I determined feeding preferences of grasshoppers by quantifying the leaf damage as volume of leaves (mm³) consumed by grasshoppers on each plant species. The results demonstrated that grasshoppers consumed more of M. sinensis ‘Zebrinus’ (p = 0.02) than of A. gerardii in the experiments with juvenile plants, but the results showed no feeding preferences in the experiments with leaves (p = 0.5). These results suggest that the feeding behavior of grasshoppers differs under natural and artificial conditions, and the resistance of plant leaves may change after they have been clipped. The data on grasshoppers feeding on M. sinensis ‘Gracillimus’ versus B. curtipendula are currently being analyzed.