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Project description

Biological Control of the Red Gum Lerp Psyllid, Glycaspis brimblecombei Moore, a New Pest on Ornamental Eucalyptus spp. in California. (99BC005)
Program UC IPM competitive research grants program
D.L. Dahlsten, Biological Control, UC Berkeley
Host/habitat Landscape Trees and Shrubs; Eucalyptus
Pest Redgum Lerp Psyllid Glycaspis brimblecombei
Discipline Entomology
Biological Controls
Start year (duration)  1999 (Three Years)
Objectives Document the seasonal distribution and abundance of the different life stages of G. brimblecombei and any endemic natural enemies on several species of Eucalyptus in northern California.

Develop an efficient monitoring method to study population fluctuations and to evaluate control attempts.

Study the effect of temperature and rainfall on the seasonal fluctuations of G. brimblecombei and its endemic and introduced natural enemies.

Screen and select natural enemies from Australia for introduction and evaluate the impact of the selected natural enemies on G. brimblecombei.

Implement a statewide biological control program for G. brimblecombei.

Final report In the first part of this project we have implemented two sampling techniques for the red gum lerp psyllid (traps for adults and foliage sampling for immature stages) and we determined that trap counts of female adults are effective as a monitoring tool. We expanded our monitoring program to 16 counties with 29 monitoring sites. The second part of the project was to implement the biological control of the psyllid. In Australia we collected a number of natural enemies (parasitoid wasps), and reared them from lerp psyllid mummies in our quarantine facility at UC Berkeley. We selected one parasitoid for release in California. The parasitoids were reared in insectaries at Berkeley and CDFA in Sacramento, and from 2000 to 2002 we released them in all counties of the state with significant red gum lerp psyllid populations. We have confirmed recoveries at all sites where traps are present, and surveys have shown establishment in many other areas, both near release sites and in areas where the parasitoid has spread naturally. At all sample sites where long-term data is available, psyllid female adult counts have dropped in 2002 by 37.1% from average counts in the year before the parasitoid was established. Most of the areas with improvement are near the coast, with the southern California coast having the largest improvement (21% of levels before parasitoid establishment). Our sites in California's Central Valley, however, have not shown improvement with parasitoid establishment. The evidence indicates that colder winter climates do not to favor the psyllid's natural enemies, including the released parasitoid. We are currently investigating the problems associated with biological control of the psyllid in the Central Valley.

In the past year of the this project we have significantly increased in our understanding the extent and population levels of this psyllid throughout the state, and have completed the discovery and mass releases of a promising biological control agent. We have implemented two sampling techniques (traps and foliage sampling) and have determined that traps are effective as a monitoring tool. We are currently monitoring 29 sites in 16 counties. Most of these areas have damaging levels of lerp psyllids, but the highest levels so far observed are in the Los Angeles area. Our initial monitoring suggests the psyllids are most damaging in moderate climates without extremes of heat or cold. We collected in Australia a number of natural enemies (encrytid parasitoid wasps), reared them from lerp psyllid mummies in our quarantine facility at UC Berkeley, and selected one as our first biological control agent. This parasitoid, Psyllaephagus bliteus, proved to be safe in our tests (i.e., does not negatively affect other psyllids such as the melaleuca psyllid). The P. bliteus parasitoids are being reared and released currently (17 counties so far) in large numbers as we expand production in cooperation with CDFA Biological Control Facility in Sacramento. In 10 counties we have confirmed recoveries which indicate, that the parasitoid is established. The parasitoid has spread to several counties without release areas, and preliminary evidence shows control of psyllid numbers in several locations.

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