By ANNE BESTON environment reporter
Biosecurity authorities are investigating the possible discovery of a virus capable of devastating New Zealand's stonefruit industry.
A Waikato orchard has been cordoned off and a restriction notice prohibiting movement of vegetation put in place after a single plum tree was suspected of being affected by
plum pox potyvirus.
The Ministry of Agriculture and Forestry is surveying surrounding orchards and carrying out laboratory tests both here and overseas.
If testing confirms its presence, New Zealand's $60 million to $70 million annual stonefruit industry would be at serious risk. The virus causes 90 to 100 per cent crop failure and chemical spraying was not an option, said MAF plants biosecurity director Richard Ivess.
Initial tests at New Zealand's national centre for disease and pest control were so far negative, said MAF national adviser on plant pest surveillance and response, Barney Stephenson, but testing was continuing both here and in the US.
"Our guys have never had to conduct tests for it before and so far tests are negative but there is the possibility of low concentrations of the virus being present and then you get a false negative result," he said.
Overseas outbreaks of plum pox potyvirus, also known as sharka, have caused whole orchards to be destroyed. The disease is carried by aphids and infected plant stock or propagative material such as budwood.
Plum pox was discovered in the US in 1999 and Canada in 2000. Many new varieties of stonefruit trees here are imported from the US.
Summerfruit New Zealand manager Marie Dawkins said growers were hoping the Waikato discovery, on a non-commercial orchard growing about 500 plum and apricot trees, was a false alarm.
"This is the worst one possible for the industry," she said.
There was no risk to human health from eating fruit from affected trees, Mr Ivess said.
Plum pox
* Infection devastates yield and the fruit is often misshapen and blemished.
* Commonly spread by grafting and aphids, it affects fruit including peaches, apricots, plums, nectarines, almonds and cherries
* It can take up to three years for infected trees to show symptoms.
* Pictures of plum pox virus are available on MAF's website and Summerfruit NZ
* Exotic Disease and Pest Emergency Hotline 0800-809-966.
Herald Feature: Environment
