Dock Leaf Beetle, Gastrophysa viridula Deg., Herbivory on the Mossy Sorrel, Rumex confertus Willd: Induced Plant Volatiles and Beetle Orientation Responses

The invasive weed Rumex confertus Willd. (mossy sorrel) is fed upon and severely defoliated by Gastrophysa viridula Deg. (dock leaf beetle). We report volatile organic compound (VOC) induction when one leaf on R. confertus was damaged by G. viridula adults to better understand plant responses to herbivory. The R. confertus volatile blend induced by G. viridula feeding included three green leaf volatiles (GLVs; (Z)-3-hexenal, (Z)-3-hexen-1-ol, (Z)-3-hexen-1-yl acetate) and terpenes (linalool, ß-caryophyllene, ß-farnesene). Overall, R. confertus that had been damaged by G. viridula released far greater concentrations of these six VOCs than control plants. Male and female of G. viridula had no significant attraction or repulsion to (Z)-3-hexen-1-ol or ß-caryophyllene. A significantly greater proportion of female and male beetles were attracted to (Z)-3-hexenal (5 ng×min-1 = 300 ng×hr-1) and (Z)-3-hexen-1-yl acetate (5 and 25 ng×min-1), in the range of induced concentrations emitted by a single injured leaf.