Threat To Australian Softwood Plantations

Originally from California and Mexico, radiata pine is being attacked in its native home by the three-pronged threat of urbanisation, disease, and feral goats, according to CSIRO’s Dr Colin Matheson.

“Long-term successful breeding of trees, like many agricultural crops, needs access to native wild genetic resources for genes to remain healthy and viable. But because of the risk of bringing the disease pitch canker to Australia, we can no longer import seed from overseas.

“And disease-free stands of the pine overseas are being wiped out by other agencies.

“In California the three natural stands of radiata along the coast have been reduced in recent years by urbanisation and are now being decimated by an outbreak of pitch canker. This will eventually kill many of the trees,” says Dr Matheson.

“On Guadalupe, one of the two Mexican islands where radiata occurs, the species is likely to become extinct as goats eat any seedlings that appear.”

Dr Matheson says that Australia depends heavily and increasingly for its timber supplies on pine plantations, and all species of plantation pines in Australia are susceptible to the disease.

“If pitch canker were to appear here, I believe it would be a very serious problem,” he says.

At a recent international workshop held in Canberra, plantation owners agreed to a range of proposals to boost the genetic conservation effort in Australia and New Zealand. This included further planting of seed collected by CSIRO from the natural stands in America, and imported into Australia and New Zealand in 1978 before pitch canker became a problem.

A workshop organised by CSIRO in California concentrated on how pitch canker attacks the tree and how it is spread.

Dr Michael Devey of CSIRO Forestry and Forest Products describes the symptoms of the disease: “Initially dead tips over the crown, then resin impregnation of the wood and eventually resin bleeding from the stem followed by death of the tree.“We have proposed a project to study the genetics of resistance and to find resistant trees”, he says.

The pitch canker project will also boost conservation efforts because Californian trees will be tested along with elite trees from other countries and seeds from Californian trees resistant to pitch canker will be made available there.

Growers of softwoods have placed emphasis on breeding for greater productivity and disease resistaance, particularly through the efforts of the Southern Tree Breeding Association and State Forests of New South Wales for radiata pine and the Queensland Forest Research Institute for other tropical pines in Queensland.

Logs from radiata plantations are currently worth about $400 million a year. The benefits of breeding were estimated as about $32 million a year in 1995 in wood volume terms alone, and could rise to more than $120 million a year after 2000. It is hoped that testing for resistance to pitch canker in California will allow resistant varieties to be incorporated into Australian breeding programs.

More information :E-mail: Mick.Crowe@ffp.csiro.au