The Impact of Exotic Forest Pests in Australia
and New Zealand

Ross Wylie

Introduction
In the past, the geographic isolation of Australia and New Zealand has provided a natural barrier to the entry of pests and diseases, while the duration of sea travel produced an enforced period of quarantine on goods and people. However, the ever-increasing volume and speed of people and cargo traffic have eroded these natural defenses, and the international trend toward trade liberalization has placed added pressure on quarantine systems. In both Australia and New Zealand, forestry makes a considerable contribution to the national economy, and most of the tree species used in plantation programs are exotic. Freedom from major pests and diseases that affect these trees in other countries conveys a competitive advantage to the industry, hence the importance of effective quarantine. There is a need, as well to protect the native flora and fauna that, because of past isolation, are particularly unprepared to combat or compete with exotic organisms.

Both countries have had several very costly experiences with exotic borers and tree pests. Some examples are provided below.

Fivespined bark beetle, Ips grandicollis-Australia
I. grandicollis was accidentally introduced into Australia in 1943 in pine crate timber from the eastern United States and is now well established in all mainland States. It mainly infests recently felled Pinus trees and logging debris, but when populations are high, it can attack and kill living trees. Its most serious impacts have been in association with wildfire and drought. For example, following fires in Pinus plantations in Queensland in 1994, attack of damaged trees by the bark beetle within 6 to 10 weeks necessitated rapid salvage of the timber and its storage under water spray. Some material could not be salvaged in time, and losses due to the beetle and its associated sapstaining fungus totaled several million dollars (Fig. 1).

Figure 1. Salvage of fire-damaged Pinus elliottii in Queensland, Australia.

West Indian drywood termite, Cryptotermes brevis-Australia
C. brevis, regarded as the most destructive drywood termite in the world, is a serious pest of timber in buildings and furniture and has been widely distributed from Central America through the tropics and subtropics. It was first recorded as established in Australia in southeast Queensland in 1966, and it is believed to have been introduced with movement of materials during World War II. Since its discovery here, it has been the subject of a containment program, funded by the Queensland government, which has prevented the spread of the pest and kept its numbers in check. Costs to date of detection surveys and fumigation of infested buildings and furniture total about $A 5.5 million, a fairly small amount when compared with the $US 300 million spent annually by house holders in Florida where the pest is rampant (Fig. 2).

Figure 2. Fumigation of Parliament House, Brisbane, Australia, in 1979 to eradicate an infestation of West Indian drywood termite.

Sirex wood wasp, Sirex noctilio Fabricius - Australia and New Zealand
S. noctilio is believed to have been established in New Zealand about 1900 and in Australia in 1952. It is one of the more significant forest insects introduced into the Southern Hemisphere and has been involved in devastating outbreaks in Pinus plantations, farm woodlots, and windbreaks in both countries. For example, in New Zealand in the 1950s, S. noctilio destroyed an estimated 30% of 120,000 ha of pine plantations within a land area of 20,000 km^2. The most seriously affected stands lost 90% of their growing stock. An outbreak of S. noctilio in Pinus radiata plantations in southeastern Australia in 1987 resulted in the death of 1.8 million trees worth about $A 5 million. A considerable amount of money has also been spent on developing and implementing biocontrol programs involving a parasitic nematode and wasp parasitoids (Fig 3).

Figure 3. Sirex noctilio on stem of Pinus radiata.

Current concerns
There is close collaboration and exchange of information between Australian and New Zealand quarantine and forestry services on issues relating to exotic tree and timber pests. Examples include joint working parties on pine pitch canker, Asian gypsy moth, and forest health monitoring. In Australia, import risk assessments have recently commenced on import of coniferous timber from North America and New Zealand, and on import of wooden packaging material from Asia. A matter of great concern to Australia currently is the risk posed by the international movement of tree germplasm, in particular the illegal importation of eucalyptus seed. This may harbor organisms such as guava rust, which could have a devastating impact on Australia's eucalypt-dominated ecosystems.

Elliott, H.J., Ohmart, C. and Wylie, F.R. 1998. Insect Pests of Australian Forests: Ecology and Management. Inkata Press, Melbourne. 214pp.

Peters, B.C. 1990. Infestations of Cryptotermes brevis (Walker) (Isoptera: Kalotermitidae) in Queensland, Australia. 1. History, detection and identification. Australian Forestry 53: 79-88.