The role of carbon dioxide as an orientation cue for western corn rootworm larvae within the maize root system: implications for an attract-and-kill approach

Abstract

Background: Western corn rootworm larvae use CO2 to locate maize roots. However, the importance of CO2 as a specific orientation cue close to maize roots has not been investigated unequivocally. This study aimed at elucidating the effect of CO2 -emitting capsules in combination with a soil insecticide (Tefluthrin = attract and kill) within the root system. We hypothesized that the capsules would result in aggregation of the larvae at the soil insecticide, thus increasing its efficacy. A nondestructive observation device was used to study larval distribution and behaviour.

Results: Spatial analysis of distance indices (SADIE) revealed aggregation of the larvae around the capsules in an attract-and-kill treatment after 4 h, which was not found with the conventional treatment without the capsules. However, larval mortality did not differ between treatments.

Conclusion: CO2 is a weak attractant for western corn rootworm larvae within the root system. Consequently, an attract-and-kill strategy based on a CO2 product will not contribute to better control compared with conventional Tefluthrin applications. Host-specific compounds, combined with a CO2 source, should be used to target more larvae, making attract and kill a feasible management option against this pest.

Keywords: Diabrotica virgifera virgifera; Tefluthrin; orientation cue; root herbivore.