While we did not find effects of root herbivory on foliar
nitrogen levels, photosynthesis, or biomass that would
explain the belowground–aboveground interactions in
our bioassay, we did record marked differences between
treatments with respect to terpenoid quantity and distribution.
Root feeding by A. lineatus enhanced terpenoid
levels in both mature and immature leaves.
Foliar terpenoids in cotton deter feeding by leafchewing
insects such as S. exigua (McAuslane and
Alborn 2000). Our results suggest that the reduced
performance of S. exigua on plants that had been
previously exposed to root herbivory are likely the
result of the wireworm-induced increase in foliar terpenoid
levels. These findings suggest the existence of a
previously unreported interaction between above- and
belowground herbivores, mediated by the induction of
secondary plant compounds in the shared host plant.