New eucalypt feeding insect established in NZ

Friday 19 Jan 2018

 
The red gum lerp psyllid, Glycaspis brimblecombei is now established in New Zealand. The psyllid was originally detected on 5-year-old Eucalyptus camaldulensis in northern Canterbury in early winter 2017. A well-established population appeared to be present and MPI has now stood down its response, opting not to eradicate in this instance.

This psyllid is native to Australia and has invaded eucalypt growing regions around the world, including North and South America, Africa, and Europe. Its hosts are in the Symphyomyrtus sub-genus (favourite food for most euc pests here). The preferred host species is probably E. camaldulensis, while other notable, but less susceptible, hosts are the adult leaf forms of E. nitens and E. globulus.

Red gum lerp adults are efficient dispersers and known overseas to spread rapidly once established. Numbers can rapidly increase, with females recorded laying up to 700 eggs in total in clusters of 50-75. This pest uses its piercing mouth parts to suck sap from its host tree, thereby damaging the host. The juveniles (nymphs) also secrete a distinctive waxy protective cover over themselves, called a lerp. It is unknown how many generations a year this psyllid will complete, but anywhere from two to four is likely based on overseas data.

The most common damage from this pest is leaf discoloration. However, in heavy infestations, severe leaf drop and twig dieback can occur. In California, the severe infestations of this psyllid facilitate the attack of secondary pests, such as long horn beetles (e.g., Phoracantha spp.), and without proper management, severe, repeated attacks can result in tree death. Other nuisance impacts may come from the honeydew the psyllid secretes and the associated sooty mould that grows on it, as well as wasps attracted to the honeydew.

Eucalypts in New Zealand are already hosts to numerous sap sucking psyllids, including the closely related species Glycaspis granulata. Glycaspis granulata is attacked by the self-introduced parasitoid Psyllaephagus bliteus. This very same parasitoid has been introduced into multiple countries to control G. brimblecombei with variable success. Lab experiments overseas have shown this parasitoid can attack and complete development on all juvenile life stages. We consider there is a high likelihood that this parasitoid will be effective here against both hosts. Generalist predators such as ladybirds and spiders are also likely to feed on this psyllid but are unlikely to have a significant impact on pest numbers.

Source: Forest Health News, Scion

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