Integration of tactics for management of Eucalyptus herbivores: influence of moisture and nitrogen fertilization on red gum lerp psyllid colonization

Abstract

AbstractMoisture stress and fertilization have been reported to both increase or decrease susceptibility of plants to herbivory. In the Eucalyptus (Myrtaceae) system in California, cultural practices that maintain sufficient moisture levels in the living outer bark contribute to the resistance of the trees to the invasive eucalyptus longhorned borer, Phoracantha semipunctata (Fabricius) (Coleoptera: Cerambycidae). However, a community of fluid‐feeding psyllids has also been introduced into the state and it was unclear if water management practices that reduce susceptibility to the borer enhanced susceptibility to the psyllids. The results of irrigation and fertilization field trials demonstrated that low water applications and high levels of fertilization resulted in higher levels of red gum lerp psyllid, Glycaspis brimblecombei Moore (Hemiptera: Psyllidae), populations on the foliage than on trees treated with higher levels of irrigation and no fertilization. There were no differences in levels of parasitization of the psyllids by Psyllaephagus bliteus Riek (Hymenoptera: Encyrtidae) under the various treatment regimes. Consequently, it is possible to integrate compatible cultural practices and the use of natural enemies to manage populations of both the borer and the psyllid.