Papaya ringspot disease: Overview

Have you seen papaya ringspot disease?

Papaya ringspot disease causes distinctive symptoms on papaya (papaw) plants.

If you suspect papaya ringspot disease and are outside the pest quarantine area call us on 13 25 23.

Papaya ringspot diease on green fruit-species

General information

Papaya ringspot disease (caused by Papaya ringspot virus - type P; PRSV-P) is a devastating pest of papaya/papaw (Carica spp.) that was first found in south-east Queensland in 1991. There are 2 papaya ringspot biosecurity zones, (PDF, 768KB) and movement restrictions are used to minimise the spread of the virus.

The virus poses a serious threat to Queensland's papaya industry, which is predominantly in central and north Queensland. The value of the Australian papaya industry was estimated at $25-30 million in 2010, with 95% of this coming from north Queensland.

PRSV-P can also infect some members of the cucurbit family (e.g. cucumber, melon, pumpkin and squash).

A second (closely related, but separate) disease of cucurbits is caused by Papaya ringspot virus - type W (PRSV-W). PRSV-W causes similar symptoms to PRSV-P, however only infects cucurbits. There are also a number of other common and widespread viruses that cause similar leaf mosaic symptoms on cucurbit plants.

Overview

What causes papaya ringspot disease?

Papaya ringspot disease is caused by Papaya ringspot virus - type P (PRSV-P).

What plants can PRSV-P infect?

PRSV-P infects and causes significant symptoms on papaya/papaw (Carica spp).

The virus also infects some species of cucurbit (cucumber, melon, pumpkin and squash), howeer does not cause significant damage to these plants.

PRSV-P only infects plants and is not harmful to people or animals.

What does it look like?

PRSV-P symptoms on papaya/papaw include:

  • the earliest symptoms are yellowing and vein-clearing of young leaves
  • distinctive ringspot patterns on fruit consisting of concentric rings and spots, or c-shaped markings - these markings persist during ripening and can darken to become orange-brown rings as the fruit matures
  • conspicuous yellow mottling of the leaves - sometimes followed by severe blistering and leaf distortion
  • dark green streaks and sometimes rings on the leaf stalks and stems
  • depending on the age of the plant when infected, fruit set is usually reduced and plant vigour declines
  • fruit quality, particularly flavour, is adversely affected.

PRSV-P symptoms on cucurbits include leaf mosaic and mottling.

How is PRSV-P spread?

Papaya ringspot disease is spread from plant-to-plant by aphids, which are small sap-sucking insects. There are many species of aphids that are capable of transmitting the virus.

When an aphid feeds on an infected plant, its mouth become contaminated with the virus, within a few seconds. When the aphid then moves to the next host plant to feed, the virus is transmitted.

No other insects are known to transmit the disease.

Papaya ringspot disease does not survive in soil or dead plant material.

The movement of infected papaya plants and cucurbit seedlings can spread the virus over long distances and is the most likely pathway for this disease to spread.

Where is PRSV-P now?

PRSV-P has only been detected in South-East Queensland. It is relatively common in backyards in Brisbane's northern suburbs. The rate of disease spread appears low.

To date it has not been found in Central or North Queensland.

The current distribution of PRSV-P will be confirmed by state-wide surveys in 2012. You can help with this survey by looking out for symptoms and reporting them to Biosecurity Queensland on 13 25 23.

How is the disease managed?

There is no cure for papaya ringspot disease.

On commercial plantations the early detection and prompt removal of infected plants can contain a localised outbreak. However once the disease becomes established, diseased trees and severely affected blocks should be destroyed, as they provide a source of infection for further spread.

In non-commercial situations such as home gardens, infected plants should be selectively removed as soon as symptoms are noticed.

Control programs

The presence of PRSV-P in south-east Queensland is monitored by Biosecurity Queensland.

The declaration of the Papaya Ringspot Pest Quarantine Area (PQA) under Queensland's Plant Protection Regulation 2002 legislation is the key strategy in restricting the movement of prohibited plants (papaya or cucurbits) into the rest of Queensland or other states. The PQA aims to prevent PRSV-P being introduced into the major papaya growing areas of Central and North Queensland.

Further information

Last updated 22 June 2012