California has been the recipient of at least seven invasive psyllid species from Australia in the last 20 years. One of these colonizes Syzigium while the others, including two lerp-forming psyllids, are specialists on Eucalyptus species. The psyllid populations cause growth deformation and may cause death of their host trees. Biological control programs have been successfully implemented against three of the species and a program is underway to control a fourth. However, control of the spotted gum lerp psyllid may also reduce populations of the commensal lemon gum psyllid that colonizes the lerp of its host.