If you have eucalyptus trees, you might have noticed white, crusty growth on the leaves. Or maybe you saw a sticky, blackened mess of fallen leaves under a eucalyptus tree. These are signs of the redgum lerp psyllid, one of the most common psyllid pests that damages eucalyptus trees in California.

Leaves of a river red gum eucalyptus tree covered with redgum lerp psyllids. The white growths are the “lerp” produced by the immature (nymph) stage of the insect. [Credit: Jack Kelly Clark]

The adult psyllid is very small and as nymphs, they are concealed under a waxy cap, or lerp. As they feed, they excrete honeydew which can lead to the growth of black sooty mold, the source of those sticky leaves under the tree.

Adult, late-instar nymph, eggs, and the whitish cover of a nymph of eucalyptus redgum lerp psyllid. [Credit: Jack Kelly Clark]

Although under biological control in coastal areas, this pest is still a problem under some growing conditions and on specific Eucalyptus species. Cultural practices to manage lerp psyllids, such as avoiding fertilization of eucalyptus trees and pruning only when and where needed, can help reduce lerp psyllid problems.

The newly revised and expanded Pest Notes: Eucalyptus Redgum Lerp Psyllid, authored by entomologists Timothy D. Paine, UC Riverside; Kent M. Daane, UC Berkeley and UC ANR Kearney Agricultural Research and Education Center; Steve H. Dreistadt, UC IPM Program; and Raymond J. Gill, California Department of Food and Agriculture, contains detailed information about the identification, biology, and management of this pest.

This revision has more information about the lerp psyllid's biology and damage they cause on eucalyptus, a list of eucalyptus trees resistant to this pest, and an expanded section on biocontrol, with detailed information about the imported parasitic wasp that only attacks redgum lerp psyllid.

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