Wasps Enlisted in Effort to Save Eucalyptus Trees

Thousands of tiny wasps from Australia will be released this month in Orange County and throughout California to prey on another insect that is bleeding some of the state’s eucalyptus trees to death.

Local officials and tree lovers are hoping the metallic-green wasps, each about the size of a rice grain, will slow the red gum lerp psyllid.

The tiny insect, also from Australia, was discovered in California in 1998 and has quickly worked its way through the state, ravaging eucalyptus trees.

In Orange County, “it has caused considerable defoliation of eucalyptus trees and also created sticky messes,” said Rick LeFeuvre, the county’s agricultural commissioner. “We prefer that the lerps not be here.”

Psyllids feed on eucalyptus tree fluids and leave a sticky substance on leaves that entomologists call honeydew. They also create lerps, minuscule domes of crystallized honeydew, on leaves to protect their young.

All of this causes leaves to drop to the ground, where they stain sidewalks, plug up pool filters and fill storm drains. Eventually the tree may die.

Hoping to combat the psyllid without insecticides, scientists went to the psyllid’s homeland to find a natural predator. A species of wasp about which researchers know very little may be the one, said Donald Dahlsten, an entomology professor at UC Berkeley.

The female of the wasp species, which has not yet been named, can penetrate lerps, paralyze the nymph and lay eggs inside its body, thereby killing the young psyllid, Dahlsten said. After hatching, each wasp larva chews its way out of the body and escapes the lerp to begin the cycle again. Dahlsten said the wasps pose no threat to humans or agriculture.

“It’s a wonderful, wonderful solution,” LeFeuvre said. “It helps reduce pesticide use; it’s a win-win for everybody.”

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Fighting a Tree-Sucking Pest

UC Berkeley scientists are studying a tiny wasp parasite they hope will eradicate an insect pest that weakens eucalyptus trees by sucking the sap from leaves and by blocking photosynthesis.

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Source: UC Berkeley Center for Biological Control