Asian citrus psyllids transmit a disease that can ruin your oranges. Even worse, Argentine ants protect them in exchange for the psyllids' delicate ribbons of sugary poop, called honeydew. So, researchers are helping orange growers fight back with invisible lasers, ghastly wasps and more trickery.

A tiny insect called the Asian citrus psyllid is threatening your oranges, lemons and limes. Smaller than a grain of rice, the agricultural pest sucks the sap from citrus trees and in doing so spreads a disease that ruins the fruit and eventually kills the citrus trees. “It's pretty straightforward to tell if you have an Asian citrus psyllid infestation in your citrus,” says Mark Hoddle, who leads a laboratory at UC Riverside that studies the pest and how to beat it. “Just check the tender young green leaves at the tips of the branches. If you see the white curly cues, the insect poop dripping off of those leaves, that's almost certainly a characteristic symptom of an Asian citrus psyllid infestation.” Hoddle's team is studying novel ways to keep psyllids out of citrus orchards, but that task is complicated by the psyllid's relationship with another insect, the Argentine ant. “Their relationship is rather sinister,” says Hoddle. “The Argentine ants harvest the honey dew that the Asian citrus psyllid nymphs excrete because it's nice and sugary and the ants love eating sugar. In return for providing that sweet delicacy, the ants protect the Asian citrus psyllids from their natural enemies like the predators and the parasitic wasps that we have introduced from Pakistan.” “The psyllids need protection from the ants because they lack defense systems,” says Hoddle. “They have recruited mercenaries to protect them.” So to protect the valuable citrus industry, Hoddle and his team are going after the psyllids' ant bodyguards.

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