When plants are bitten by insects, they release a chemical scream—a cocktail of compounds that travel through the air. Some deter pests directly by confusing or repelling them; others indirectly protect plants by summoning predatory ants or parasitic wasps. Still others raise the alarm in parts of the plant that aren’t yet under attack, telling them to ramp up their defenses in preparation. These same alarms can spread over entire fields, warning other plants to prep their defenses. We can’t perceive these signals, but to plants, they’re as foreboding as wailing sirens.
But Peng-Jun Zhang and Xiao-Ping Yu from China Jiliang University have shown that one of the world’s worst agricultural pests—the silverleaf whitefly—can hack this communication system. When the whiteflies bite, they somehow change a plant’s airborne warnings so that they convey information about the wrong threat. Deceived, the neighboring plants invest in the wrong defenses and become more susceptible to the whiteflies. These pests, by seeding entire fields with faulty intelligence, can prime the plants ahead of them for their arrival.
This might help explain why the silverleaf whitefly is so devastatingly invasive. It causes billions of dollars’ worth of damage every year and feeds from some 500 types of plants—squash, cucumber, cotton, melons, eggplant, cabbage, and more. Wherever it goes, it drains nutrients from its hosts, covers their leaves in sticky liquids that promote the growth of molds, and infects them with devastating viruses. Originating somewhere in Africa, it has spread across the entire world over the past two centuries.