Redgum lerp psyllid, Glycaspis brimblecombei, is a sap-sucking insect on eucalyptus. It is not a wood-boring beetle. UC IPM says it arrived in Los Angeles in 1998 and now occurs on hosts throughout California. It prefers river red gum, Eucalyptus camaldulensis. Other gums can carry it. Some species stay lightly infested.

The lerp is a waxy cap on the leaf, often whitish, sometimes darkened by sooty mold. Honeydew drips. Cars, decks, and sidewalks get sticky. That mess is the usual reason people call. It is a different problem from eucalyptus longhorned borers.

Branch Pro San Diego is a referral service. We connect you with licensed, insured independent local tree professionals. You hire and pay the professional directly. We don’t spray, inject, or remove eucalyptus.

How do you tell lerp from a borer?

Lerps sit on leaves. Borer clues are in the wood: holes in bark, ooze, dieback from galleries. Common tree pests uses lerp as a differential. This page is the lerp task.

UC says nymphs live under the cap. Adults are small and greenish to yellow. The number of old caps is a poor count of live insects. Some nymphs leave empty covers. Parasitized nymphs can sit under a cap that still looks occupied.

A river red gum over a Clairemont driveway and a silver-dollar gum in a Point Loma courtyard are not equally preferred hosts. Name the eucalyptus if you can.

What does UC say actually works?

UC puts cultural care and biological control ahead of a product.

  • A tiny parasitic wasp, Psyllaephagus bliteus, now occurs where the psyllid occurs. UC says it provides substantial control in coastal areas when pesticides don’t disrupt it. Inland heat reduces that help.
  • Drought stress makes lerp (and borers) worse. Water at the outer canopy, not against the trunk. Don’t run a lawn-style shallow cycle.
  • Don’t add nitrogen. Succulent new shoots are what egg-laying females prefer.
  • If you prune for honeydew drip, UC says to prune eucalyptus in southern California in December or January, except for dead or hazardous wood, which can come off when it appears. Fresh wounds also attract longhorned borers at other times.

Foliar sprays are a poor fit. The lerp shields the nymph. UC says oil-and-soap mixes are not highly effective and only last a short time on small trees. Systemic products have mixed, sometimes disappointing results, and they can harm the wasp. UC prefers soil or bark methods over trunk injection when a systemic is even on the table, because injection is a wound.

Don’t treat coastal eucalyptus just because the sidewalk is sticky. Ask whether the wasp is already working.

When is a professional visit worth it?

Call when honeydew is a slip hazard, when defoliation is heavy on a preferred host, or when you also see borer-style holes in the wood. Those can travel together on a stressed tree. Tree health diagnosis is the identification path. Eucalyptus removal is a separate scope if the tree is past keeping.

A City street eucalyptus is not a private-yard tree. Confirm ownership before anyone cuts. Use Get It Done for a City of San Diego street tree.

For paid tree work, look up the license on the CSLB license lookup. An active C-49 Tree and Palm license or an active legacy D-49 can both be valid. California’s current minor-work threshold is an aggregate price under $1,000, with extra conditions. A pesticide application can require its own license.

Frequently asked questions

Are lerps the same as scale insects?

They can look similar on a leaf. Redgum lerp psyllid is a psyllid under a waxy cap. Identification still belongs to a qualified person before anyone sprays.

Should I pressure-wash the honeydew off the tree?

Washing pavement is a different job from treating the insect. Hard washing foliage can add stress. Ask before you blast the canopy.

Will the tree die from lerp alone?

UC says heavy defoliation weakens trees and can raise the risk from other pests and diseases. Death is not automatic from sticky leaves.

Can Branch Pro prescribe imidacloprid on the phone?

No. UC’s own efficacy notes are mixed, and coastal biocontrol argues against a casual systemic. The independent professional inspects the tree.

Get connected with a local pro

If the eucalyptus is on a conductor, call 911 and SDG&E at 1-800-411-7343 first. For honeydew, defoliation, or a keep-versus-remove question, call (858) 400-4423. We’ll connect you with a licensed, insured independent local professional. Describe the gum species if you know it, the drip target, and whether you also see holes in the bark. You hire and pay that professional directly.