Greening-infected citrus trees emit an odor that not only attracts Asian citrus psyllid, which spreads the disease, but also a minute wasp that feeds on the psyllid.
Research led by Lukasz Stelinski, associate professor of entomology and nematology at the University of Florida's Citrus Research and Education Center in Lake Alfred, examined the interactions among the species.
When trees are infected with citrus greening, they emit an odor—methyl salicylate—that makes them more attractive to Asian citrus psyllids, according to a news release.
Although the infected trees are less nutritious to psyllid, the mechanism may encourage the insect to spread the disease.
Stelinski's group injected a minute wasp, which is a natural psyllid enemy, into the study.
When they put the wasp in an olfactometer that can deliver different scents, they found the wasp was drawn toward the methyl salicylate as well as limonene, which is emitted by citrus plants.
They also found the wasps were more apt to attack psyllids on greening-infected plants and on methyl salicylate-treated plants than on healthy ones.
Their work was published recently online in the journal "Frontiers in Ecology and Evolution.