Wasp larvae that eat aphids alive may save apple crops

Insecticides are more effective. But you lose your organic certification

K751NK Meadow with wild flowers around the base of an apple tree

Jan 11th 2023

Few insects 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%.

This article appeared in the Science & technology section of the print edition under the headline “Flower power!”