Trees are under attack in 30 California counties from the redgum lerp psyllid, Glycaspis brimblecombei, a small, flying insect that feeds on plant juices. It has caused much concern in the state since it was first found in June 1998 in Los Angeles County. Collected on 16 different varieties of eucalyptus in California, the psyllid is causing the most trouble on redgum, Eucalyptus camaldulensis, a common ornamental species in the state. After infestation, trees rapidly lose their leaves and begin to produce a sticky honeydew that dirties cars, buildings and sidewalks. It is not known how often the trees can defoliate and still survive.
Dahlsten has shown that certain species of Psyllaephagus parasitic wasps that he collected last summer in Australia may be able to bring the psyllid population under control by laying eggs within the insect bodies and destroying them. The wasps have been under surveillance for the last year at UC Berkeley. This week, 100 females will be released to treat 20 trees in Valley Village Park in North Hollywood.
"We have low numbers of parasites right now and are trying to build up our numbers," said Dahlsten, a professor of environmental science, policy and management and biological control in the UC Berkeley College of Natural Resources. "We will be releasing all summer, and we hope that the parasitoids will spread as rapidly as the other parasitoids that we have released to control other species of psyllids in the past, making multiple releases unnecessary."
Dahlsten is credited with saving the state's foliage industry in 1991-93 from a disaster on a species of eucalyptus used in the flower trade. It would have cost California's eucalyptus growers millions of dollars to control the problem year after year had Dahlsten not discovered an insect cure.
Approved by the United States Department of Agriculture Animal and Plant Health Inspection Service (APHIS), this week's release will be conducted by the Los Angeles Department of Parks and Recreation, the Los Angeles Bureau of Street Services and the Los Angeles Zoo. Additional funding was provided by the University of California's Integrated Pest Management Project and by cities and agencies in Orange, San Diego and Los Angeles counties.
Note: For further information, check Donald Dahlsten's web site. An earlier UC Berkeley news release with more detail on the lerp psyllid and the parasitic wasp is available on the web at UC Berkeley Public Affairs .