Neonate larvae of the specialist herbivore Diabrotica virgifera virgifera do not exploit the defensive volatile (E)-β-caryophyllene in locating maize roots

The behavior of the neonate larvae of the western corn rootworm (WCR) Diabrotica virgifera virgifera LeConte, a major pest of maize, was assessed in the presence of maize roots constitutively emitting (E)-β-caryophyllene (EβC). This root volatile has been shown to attract both second instar WCR and insect-killing nematodes, and may offer innovative alternatives in helping to manage WCR. Under greenhouse conditions, the maize inbred line HiII, lacking the ability to emit EβC, was planted 75 cm from the maize inbred line 201-L1, the HiII inbred genetically engineered to constitutively emit EβC. WCR eggs were infested in the center of the two lines and neonate attraction toward either root system was recorded after collecting WCR larvae established on the plants. Whereas marginally more larvae were found on EβC-emitting plants, counts of recovered WCR neonates did not significantly differ between the two lines. This supports the postulate that CO2 is the primary attractant for WCR neonate larvae. The chemical ecology of WCR larvae is discussed. A conceptual model of the foraging behavior of this pest is proposed, summarizing our current knowledge on chemically mediated interactions between WCR larvae and maize roots.