Apion miniatum Germ. Herbivory on the Mossy Sorrel, Rumex confertus Willd.: Induced Plant Volatiles and Weevil Orientation Responses

In this paper we report on the large induction of volatile organic compounds (VOCs) from a single leaf of the mossy sorrel, Rumex confertus Willd. (Polygonaceae), by herbivory of the red dock weevil (Apion miniatum Germ., Coleoptera: Apionidae). VOC blends induced by the red dock weevil herbivory included 5 green leaf volatiles (GLVs) ((Z)-3-hexenal, (E)-2-hexenal, (Z)-3-hexenol, (E)-2-hexenol, (Z)-3-hexen-1-yl acetate), two esters (benzyl acetate, methyl salicylate), and four terpenes ((Z)-β-ocimene, linalool, βcaryophyllene, (E)-β-farnesene). Not surprisingly, uninjured plants produced only small amounts of VOCs. A Y-tube experiment revealed that females of A. miniatum were attracted to the blend (blend 1) of (Z)-3-hexenal + (E)-2-hexenal + (Z)-3-hexenol + (E)-2-hexenol + (Z)-3-hexen-1-yl acetate at two concentrations of 1 and 5 ng·min. In contrast males of the red dock weevil were not attracted to any tested concentration. Moreover, females and males of A. miniatum were not attracted to any concentration of blend 2 ((Z)-ocimene + linalool + benzyl acetate + methyl salicylate + ß-caryophyllene + (E)-ß-farnesene). Yet the red dock weevil females and males were repelled by the highest concentration (125 ng·min) for both blends.