One of California’s most common landscape trees -- already under attack by nearly a dozen different insects from its native Australia -- is facing perhaps its greatest challenge in an eighth-inch pale green, plant-juice sucking bug called the redgum lerp psyllid.
And, there is little that homeowners and landscape managers can do to protect their eucalyptus trees until scientists identify and study the psyllid’s natural enemies in hopes of establishing a permanent, non-pesticide “biological control,” according to Mark Hoddle, a Cooperative Extension entomologist at UCR.
Of the dozen known eucalyptus pests now in California, the redgum lerp psyllid has been among the fastest to spread. Discovered in June 1998 in Southern California, it is now commonly found in eucalyptus landscapes from San Diego to the Bay Area.
Feeding by psyllids can seriously defoliate and weaken trees, leaving them susceptible to other pests. Infestations can be readily identified by the characteristic protective cover -- called a “lerp” -- which the nymph or immature stage of the psyllid forms as it is feeding on leaves. A lerp resembles a small white, round cap that grows to about the size of a lentil or larger.
“This insect has tons of food. It’s got great weather and nothing is stressing it out. It’s got a great life in California. We need to disrupt this great lifestyle by finding and releasing safe natural enemies to feed on the psyllid,” said Hoddle.
Present in California are several natural enemies of the redgum lerp psyllid, including two different ladybug beetles, but it is not known if they can control the psyllid without additional reinforcements.
A UC Berkeley entomologist has collected a tiny parasitic wasp from the psyllid’s native Australia and is studying it in hopes of establishing a non-pesticide biological control in California.
But, it will be at least 12 to 18 months before such a management program can begin, Hoddle said. Natural enemies need to be cleared through quarantine and deemed safe for release before they can be mass reared and distributed.