Plum pox potyvirus investigation underway

The Ministry of Agriculture and Forestry (MAF) is investigating a possible case of plum pox in a single non-commercial plum tree in the Waikato.

MAF was alerted to the find on 11 March 2003 all initial test results have shown negative. Samples have been sent to the United States Department of Agriculture for verification. These results are expected back within two weeks.

In the meantime a Restricted Place notice has been put on the property which prohibits the movement of material off the premises. A survey of neighbouring properties producing stone fruit is also underway.

Richard Ivess, Director of MAF Plants Biosecurity said plum pox is one of the worst diseases that could affect our stone fruit industry and, if tests prove positive, MAF will be taking all steps to manage the virus with the aim of eradication. Mr Ivess emphasised there was no risk to human health in consuming infected fruit.

“If plum pox was to establish in New Zealand it would seriously threaten the viability and survival of the summer fruit industry. There is no treatment for the virus and the only solution is for infected trees to be destroyed. Spraying with chemicals is not an option,” he said.

Plum pox is a notifiable disease under the Biosecurity Act 1993. Four strains of the plum pox potyvirus exist. In infected countries it is commonly spread by grafting and by aphids and can devastate fruit bearing varieties from the Prunus family including peaches, apricots, plums, nectarines, almonds and cherries, causing fruit to be unmarketable and decreasing the yield.

Infection results in a severely reduced yield and the fruit is often misshapen and blemished. Plum pox can also enhance the effects of other viruses .

Long distance spread occurs as a result of the movement of infected plant stock or propagative materials such as budwood. It can take up to three years for infected trees to show symptoms of the virus.

Summerfruit New Zealand Manager Marie Dawkins supports the approach taken by MAF and members have been contacted by the industry to alert them to symptoms.

Over the last two years, the industry has been very active in raising grower awareness to this disease, and has sent pamphlets to all growers informing them of what to look for. In 2001, Summerfruit New Zealand ran an awareness campaign for growers funded from member subscriptions. Later that year, Summerfruit New Zealand participated in a MAF plum pox simulation exercise which was effective in raising awareness of the disease. The proof of this is shown in the vigilance of the member of the industry who quickly alerted MAF to the incident after noticing possible symptoms on March 6.

Marie Dawkins said Summerfruit New Zealand wishes to highlight that any fruit affected with the plum pox virus would not be found in any fruit and vegetable outlets, as the virus renders the fruit unsaleable. The MAF investigation will not have any impact on fruit for sale in the shops.

As of December 2002, New Zealand exported $17.46 million of stone fruit and our domestic market was worth approximately $45 million. The season for exporting stone fruit is over for the year.

Plum pox has a wide distribution and is present in Turkey, Syria, Chile, India, Canada, United States of America, and most of Europe.

Symptoms of plum pox virus infection can be easily confused with other diseases and physiological conditions. However rings and roundish blotches on fruit, rings on stones and extremely high levels of fruit drop are very characteristic. Pictures of Plum pox virus are available on the websites provided below. Suspect samples can be sent to MAF by contacting the Exotic Disease and Pest Emergency Hotline 0800 809 966.

Background information on plum pox is available at http://www.maf.govt.nz/plum�pox and http:// http://www.summerfruitnz.co.nz

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