Red Gum Lerp Psyllid
The red gum lerp psyllid (RGLP) (Glycaspis brimblecombei) is a foliar pest on red gum eucalyptus trees (Eucalyptus camaldulensis). Like Eucalyptus trees, the RGLP is native to Australia. RGLP is a plant-juice sucking homopteran in the family Psyllidae. The nymphs form a protective covering of crystallized honeydew called a lerp, which protects the insects from both predators and insecticidal foliar sprays. Excess honey dew results in the growth of sooty mold. The RGLP is responsible for extensive defoliation of Red Gum Eucalyptus trees. Heavy infestations result in reduced tree health, decline and ultimately, tree loss.
Trees infested by Red Gum Lerp Psyllid have leaves covered in "lerps," blackened by sooty mold and drop leaves. Honeydew from eucalyptus trees may also be an indication of RGLP infestation.
photo A taken by William M. Ciesla, Forest Health Management International, Bugwood.org
Photo B taken by Jack Kelly Clark, University of California Statewide IPM Program
Arborjet recommends a trunk injection using IMA-jet (imidacloprid), a systemic insecticide for the control of RGLP. Imidacloprid is a nicotinoid, a synthetic chemistry structurally similar to nicotine sulfate found in tobacco, which disrupts the central nervous system in insects. Applications may be made using the Arborjet TREE I.V. or the QUIK-jet micro-injector.
When to Treat
Generally, the best seasons for injection are fall and spring, as uptake occurs when trees are transpiring. The environmental conditions that favor uptake are adequate soil moisture and relatively high humidity. Soil temperature should be above 40 degrees F for trunk injection. Hot weather or dry soil conditions will result in a reduced rate of uptake, so trees should be watered if applications are made when soil is extremely dry. If treating trees in the summer, inject in the morning for the quickest uptake. Tree health will affect treatment efficacy, so assess tree health prior to treating. For example, a declining tree (>50% canopy dieback) is a poor candidate for treatment. In Eucalyptus trees, treat when RGLP is first observed in trees for best results.
What to Expect After Treatment
IMA-jet is an effective treatment option for RGLP infestation. Trees will re-foliate, proportional to the level of infestation at the time of treatment. Best outcomes are seen when applications are made early to trees. Trees that have been repeatedly defoliated by RGLP without treatment will have a poorer prognosis for recovery.