Plant toxins can be detoxified by specialized insects. The mechanisms of this detoxification process and its influence on the natural enemies of the herbivorous insects are not yet understood. We investigate how the western corn rootworm deals with the main defence compounds of maize and how this affects the efficiency of beneficial organisms that kill the pest. This work will contribute to a fundamental understanding of the biology of an important pest insect and its natural enemies.

Many plants defend themselves with chemicals that they store in their tissues in a non-toxic form. When these tissues are damaged by, for instance, plant-eating insects the stored compounds are converted to a toxic form to ward off the attackers. In maize plants and other grasses the main chemical defense compounds are so-called benzoxazinoids (BXDs). They are stored as glucosides, which means that there is a sugar (glucose) attached to the molecule, rendering it non-toxic. Upon tissue disruption enzymes are liberated that cleave off the sugar and the BXDs become toxic. Our project builds on our discovery that specialized insects have evolved highly sophisticated mechanisms that make them immune to this maize defense. Certain caterpillars are able to reattach a sugar to BXDs in a position that makes the molecule much more stable and invulnerable to the enzymes. Highly specialized beetle larvae that feed on the roots of maize plants can even use BXDs as foraging cues and are fully resistant to these toxic metabolites. We aim to unravel the mechanisms that allow this important pest of maize to withstand BXDs and to explore if and how the insect’s enemies are affected by the toxins. The focus will be on entomopathogenic nematodes (EPN), tiny roundworms that develop and reproduce inside insect bodies and kill them within days. The work will not only generate fundamental new knowledge on chemical defenses in plants and insects, it also has great potential for pest control as it may lead to the discovery of highly effective EPN strains for the biological control of one of the world’s most destructive maize pests.