Biosecurity Threats

Biosecurity Threats

Outlined briefly below are some pest and pathogen species that pose a forest health biosecurity risk in terms of the damage they could potential pose to Eucalyptus globulus plantations. For further information refer to our field guide or consult the guides section for further reading.

If you suspect that you may have found or observed one of these exotic pests or pathogens you should urgently contact the Exotic Plant Pest Hotline on Freecall 1800 084 881 and follow their instructions.

Pests

Gypsy Moth

Gypsy moth caterpillerGypsy MothThere are 3 biotypes of Gypsy moth; 2 Asian types and an European one. The greatest limitation this species has as an invader is that females (of the European type) are incapable of flight and this limits its rate of unassisted range expansion. However, females of the Asian type are capable of flight and all strains often lay their eggs on human-made objects, such as machinery, logs, furniture etc. Therefore the potential for accidental introduction and spread is high. The first symptoms of gypsy moth infestation appear in the tops of the trees as the newly hatched larvae usually start feeding on flushing buds and expanding leaves. High populations often result in total tree defoliation.

Asian Longicorn Beetle

Longicorn Beetle (Penthea pardalis
Longicorn Beetle (Penthea pardalis)

This species has a very wide host range and could potentially be very destructive affecting Australia’s hardwood forests, fruit orchards and parkland and amenity trees. In the field the most obvious sign of this species presence, would be dead or dying trees, with circular emergence holes 9 – 11mm in diameter, and small piles of sawdust at base of trees or in branch crevices. Adults would emerge from trees in summer. Symptoms could be confused with those caused by native wood boring species.

South African Cossid Goat Moth

Recorded on Eucalyptus nitens in South Africa. The larvae are up to 60 mm long grubs with dark heads and light yellow bodies with reddish blotches. They feed greagariously in living trees, boring relanumerous galeries in the trunks of trees. Holes in the stem with wood frass and kino spilling out are often a sign of their presence. Affected trees are susceptible to wind break and further fungal attack.

South American Carpenter Worm

Prionoxystus robiniae – Carpenterworm Moth
Prionoxystus robiniae – Carpenterworm Moth
Image By Andy Reago & Chrissy McClarren [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

Originally reported from central to southern Chile and Argentina. The species feeds on various hardwood timber species and fruit trees. It is known to attack a number of eucalypt species including Eucalyptus globulus. The larvae are large stout grubs with dark heads and cream coloured bodies. They feed in living trees and bore relatively large holes in the trunk, making them susceptible to wind breakage and facilitating the entry for fungal pathogens. Adult moths can fly over considerable distances, and the pest could quickly spread if established.

Pathogens

Eucalypt rust

Leaf rust caused by Puccinia psidii
Leaf rust caused by Puccinia psidii

Puccinia psidii is a rust fungus originating from South America. It is unusual for a rust species in that it has a very large host range, mostly within the family Myrtaceae (including eucalypts). Its introduction into Australia is likely to be extremely damaging to native ecosystems as well as plantations. Tropical and sub-tropical areas are likely to be more affected due to favourable conditions. There is variation in host susceptibility both between species and between provenances within species. The rust produces lesions on young, actively growing leaves and shoots, as well as on fruits and sepals. Leaves may become buckled or twisted as a result of infection. When fruiting, massess of bright yellow or orange-yellow spores may be observed on the surfaces of affected parts. Occasionally, they may have dark brown spores. Severe rust disease in young trees may kill shoot tips, causing loss of leaders and a bushy habit. Repeated cycles of infection reduce growth and may lead to death of trees.

Coniothyrium stem canker

The common name for this disease refers to its previous name Coniothyrium zuluensis. Its is found in Africa, central and southern America and south east asia. This pathogen causes small, necrotic spots on the young green stems of Eucalyptus, which later coalesce and form large cankers that eventually girdle susceptible trees and kill their tops. Abundant kino exudation and formation of kino pockets in the xylem are common symptoms. The lesions restrict bark peeling prior to pulping.

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Phytopthora ramorum

Phytopthora ramorum-
Phytopthora ramorum

First detected in temperate areas of North America. Symptoms may vary depending on the host species. These include necrotic leaf spots, leaf blight, and even twig dieback. The most consistent and diagnostic symptom on trees are cankers that develop before foliar symptoms become evident. Cankers have brown or black discoloured outer bark often with an ooze of dark red sap. They occur on the trunk at the root crown up to 20 m above the ground, but do not enlarge below the soil line into the roots. Individual cankers are delimited by thin black lines in the inner bark and can be over 2 m in length Recent testing on Eucalyptus spp., indicates that many are susceptible. However susceptibility is likely to vary depending on species and provenance. The pathogen is aerially dispersed and given it has a wide host range (over 40 plant genera), it poses a significant threat should it be introduced.