Wasp larvae that eat aphids alive may save apple crops

strike greater fear into the hearts of orchard-owners than rosy apple aphids. These tiny bugs feed on the leaves of apple trees, draining them of nutrients. Their saliva, meanwhile, contains a toxin which causes those leaves to curl up and harden, providing an excellent place for them to shelter, including from insecticidal sprays. And the honeydew they excrete once they have extracted what nutrients they need from the sap they have ingested encourages the growth of a sooty mould that can further harm a tree. A bad rosy-apple-aphid infestation can reduce an orchard’s yield by 80%. In the battle against these aphids some propose harnessing the services of tiny wasps called and . Like many of their kin, these insects are parasitoids, a trophic status halfway between being parasites and predators. Instead of killing and then eating their prey, parasitoid wasps eat and thus kill them—or, rather, their larvae do.