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Eucalyptus Red Gum Lerp Psyllid Arrives in Arizona

Andrew Backhaus, Ph.D.

On May 19, 2005, the day the last Star Wars movie opened across the country, we were notified that eucalyptus trees surrounding Hi Corbet Field, the winter home of the Colorado Rockies at Reid Park in Tucson, Arizona were covered with small, white, sugary bubbles on their leaves. This was an ominous sign. Had the Dark Side finally invaded Arizona? Our fears were realized when we saw, firsthand, that the red gum lerp psyllid, Glycaspis brimblecombei (Homoptera: Psylloidea; Spondyliaspididae) had not only invaded our state, but arrived with a vengeance.

 Psyllids (sil΄-ids), also known as jumping plant lice, cause damage by sucking on plant juices. While resembling aphids, psyllids differ in their ability to jump when disturbed. Pysllids are also noted for the vast amounts of sticky honeydew or dried sugar that they excrete on leaves. The lerp psyllids found on eucalyptus are named for the “lerp”, the Australian aboriginal name for “house” that these tiny insects produce. The lerp is formed from the sugar and wax secretions that create a conspicuous white, conical shell to protect the young nymphs as they feed on eucalyptus leaves.

Adult Red Gum Lerp Psyllid

Lerp psyllids first appeared in southern California in 1998 from Australia, leading to widespread damage of red gum (Eucalyptus camaldulensis) trees throughout the state. Heavy populations cause leaf defoliation that weakens trees and makes them susceptible to a second insect, the eucalyptus long horned borer Phoracantha semipunctata and P. recurva. The one-two punch of these insects ultimately killed thousands of mature trees throughout California. Fortunately there is no evidence of eucalyptus long horned borers in Arizona. However, the threat from the psyllids alone is a serious threat.

Lerp psyllids tend to be fussy eaters and only attack a few species of eucalyptus, most notably red gums (E. camaldulensis) that happen to be the most widely planted eucalyptus in Arizona. They also feed on E. rudis, E. tereticoris, E. dealbata, E, resinifera and E. nitens, but avoid most other eucalyptus species. They do not attack trees outside the eucalyptus family.

In Tucson, virtually every red gum at Reid Park contained lerps. Hoping that the problem was confined to Tucson, we learned a few days later that they had also spread to Globe, Arizona and reached the Boyce Thompson Arboretum in Superior, Arizona, about 75 miles east of Phoenix. The arboretum, home to over 80-90 different eucalyptus species, includes about one hundred stately red gum specimens, all of which were infested. To date, there are no reports of infestations in Phoenix, but according to California experts it will just be a matter of time before they spread throughout the Southwest.

Lerp psyllids cannot be controlled by foliar sprays of conventional insecticides or spray oils. The waxy lerps protect the small insects inside from chemical sprays. The systemic chemical, imidacloprid is effective if applied by trunk injection or by a soil drench. In California, excellent protection has been obtained with the Mauget brand of the trunk-injectable formulation known as imicide, which comes as a liquid in ready-to-use capsules. To use, small holes must be drilled around the trunk, spaced 6 inches apart, where a tube is inserted through which the liquid drains from the capsule into the trunk. When used correctly the psyllids should be killed within fourteen days but the lerp structures remain on the leaves for several months. Fortunately, imicide treatments can provide long-lasting control even after a single injection. In Arizona, these capsules are only available from Artistic Arborist, Inc. 4519 N. 7^th Ave, Phoenix, AZ 85044, phone 602-263-8889.

California has seen a notable decline in red gum lerp psyllids since 2000, due, in part, to the introduction of a natural parasitoid wasp, (Psyllaephagus bliteus) brought in from Australia. Unfortunately, this wasp is not present in Arizona and may not thrive in our hot desert environment, even it is introduced. Experience from California indicates that eucalyptus trees should be treated with systemics as soon as lerps are observed or the consequences are likely to be tree death. In this regard let’s hope that the Force will be with us.