Root herbivory induces an indirect aboveground defense.

Indirect plant defences have largely been studied within the scope of above-ground interactions. Here we provide novel evidence that root herbivory can induce an above-ground indirect defence. Cotton plants (Gossypium herbaceum) exposed to root-feeding wireworms (Agriotes lineatus) increased their foliar extrafloral nectar production ten-fold in comparison to undamaged control plants. Mechanical root damage also yielded an increase in nectar production. In nature, extrafloral nectar production allows plants to recruit predators, which in turn protect the plant against above-ground insect herbivores. Our results show that root-feeding herbivores may alter such above-ground defensive interactions