Variation among Eucalyptus species in resistance to eucalyptus longhorned borer in Southern California.
The relative susceptibilities to Phoracantha semipunctata (the larvae of which bore through the bark and mine along the cambium of stressed trees, usually killing them) of 12 Eucalyptus species in two mixed species plantations in California, USA, are reported from studies in 1990 and 1992. These trees were stressed by water deficit resulting from a prolonged drought. Eucalyptus species that appeared resistant to the borer included E. camaldulensis, E. cladocalyx, E. sideroxylon and E. trabutii (an E. camaldulensis hybrid). Species that were more susceptible to attack were E. diversicolor, E. globulus, E. grandis, E. nitens, E. saligna and E. viminalis. Survival of trees was influenced by fine scale moisture variation resulting from slope and irrigation effects. Resistance characteristics of these Eucalyptus species did not correlate with taxonomic relatedness or bark characteristics, but did correspond to drought tolerance traits in their native habitat. Eucalyptus species that were resistant to attack by P. semipunctata were those that are most tolerant of drought in Australia.