Biosecurity alert: Dickeya dianthicola

The Western Australian Department of Primary Industries and Regional Development has confirmed the detection of Dickeya dianthicola in seed potatoes and dormant dahlia tubers in Western Australia, and is responding with measures to contain the pest, determine spread and assess the feasibility of eradication.

Dickeya dianthicola is a serious bacterium that can cause tuber soft rot and blackleg in potatoes, and can also affect some ornamental varieties, chicory and artichoke.

Growers of these crops are urged to check plants and tubers, and report any suspect symptoms.

What is Dickeya dianthicola 

Dickeya dianthicola causes soft rot and blackleg in potatoes. It is a serious pest (bacterium) that was not previously known to occur in Australia. Overseas data has indicated significant yield losses in potato crops.

Dickeya dianthicola can also infect other crops, including some ornamentals (including carnation, lily, chrysanthemum, dahlia, begonia, flaming Katy, freesia, hyacinth and iris), globe arichoke and chicory.

Other pathogens already present in Australia can cause similar soft rot and blackleg symptoms. However, Dickeya dianthicola is more aggressive and causes disease at lower infection levels.

This pest is not associated with the tomato potato psyllid.

Department of Primary Industries and Regional Development (DPIRD) response

The pest has been confirmed on four commercial potato growing properties. These four properties have been placed under quarantine. The quarantine notices stipulate movement restrictions on host plant material, soil and machinery.

DPIRD is continuing to trace the movement of potatoes and dahlia tubers to and from infected properties and to collect samples from the highest risk properties, in order to determine the extent of the outbreak as soon as possible.

DPIRD is working closely with the WA industry and national stakeholders to minimise the impact of this new pest. The Consultative Committee on Emergency Plant Pests (CCEPP) has met to discuss this detection. The committee has kept open the possibility for eradication, dependent upon further surveillance.

This particular pest is not associated with the tomato potato psyllid that was detected in Western Australia earlier this year.

The bacterium does not have an impact on human health.

Host list

  • Potatoes
  • Globe artichoke
  • Chicory
  • Begonia
  • Calla lily
  • Carnation
  • Chrysanthemum
  • Dahlia
  • Dianthus, Sweet William
  • Freesia
  • Hyacinth
  • Iris
  • Kalanchoe, ‘Flaming Katy’ which is also known as ‘Christmas kalanchoe’, ‘florist kalanchoe’ and ‘Madagascar widow’s thrill’

Trade impacts

Trade in potatoes from WA is currently prohibited due to the tomato potato psyllid outbreak, and interstate movement controls for risk material continue to apply. In response to TPP, WA is working with other state and territory governments to develop protocols to support future interstate movements of risk material.

Trade in cut flowers from WA is already subject to interstate movement conditions for other pests. At present there are no further trade restrictions in relation to Dickeya dianthicola.

The Australian Government Department of Agriculture and Water Resources will work with overseas trading partners should any issues arise.

Helping growers to maintain normal business operations

DPIRD recognises this detection comes at a difficult time for the horticulture industry, in particular potato growers, following the detection of the tomato potato psyllid earlier this year.

If issued with a Quarantine Notice, Pest Control Notice or Direction Notice under the Biosecurity and Agriculture Management Act 2007 (the BAM Act), growers cannot move or sell infected plants/tubers from properties without written approval from a DPIRD inspector, who are authorised under the BAM Act.

DPIRD is working with affected potato growers to provide approvals that can help resume their business, while at the same time making sure the pest does not spread any further. To achieve this, DPIRD is carrying out risk assessments of operations, and helping growers to develop a plan for the movement and sale of their ware potatoes.

Each property is being assessed on a case by case basis.

See the attached fact sheet - Quarantine and your business - for more information on positive samples and Notices.

Symptoms

The first symptom of the disease can be poor emergence due to rotting seed tubers. Plants wilt and typically have slimy, wet, black stems extending upwards from the rotting tuber. 

Infected tubers are macerated and have a tapioca-like appearance, but may not have the pungent smell associated with typical blackleg.

According to overseas data, Dickeya dianthicola can also cause soft rot and wilting in ornamental crops.

Dickeya dianthicola can be present in a plant without causing symptoms, particularly if temperatures remain low. Symptoms often develop after a period of hot weather, especially when plants are also stressed. 

See the attached fact sheet for more information.

How does it spread?

In potatoes, it is generally accepted the main source for blackleg infection is latently infected seed tubers.

Overseas data indicates that as infected tubers rot, the bacterium is released into the soil. It can then be transmitted through water in the soil and contaminates neighbouring tubers, and infected stems can also affect neighbouring plants through contaminated irrigation water.

Additionally, infection has been shown to spread to other tubers during storage. Overseas research indicates that Dickeya dianthicola does not survive long in soil without a host. Although bacteria can survive between potato crops in soil when there is remaining plant debris or when volunteer potatoes are present.

Management options

Generalised management techniques developed for soft rot diseases in potatoes may be useful for growers affected by Dickeya dianthicola. Refer to the soft rot web pages for further information.

Additionally, on-farm biosecurity practices, such as good farm hygiene and early reporting of suspicious symptoms should be in place to prevent the entry, establishment and spread of pests and diseases. Practical advice and information to assist is available through the Farm Biosecurity website farmbiosecurity.com.au

Reporting options

Dickeya dianthicola (Samson et al. 2005) is a prohibited organism for Western Australia. It is important any suspect disease occurrences are reported.

Growers can report any unusual plant symptoms by:

  • Calling the Pest and Disease Information Service on 1800 084 881, or
  • Sending a photo to DPIRD via the MyPestGuide Reporter app available from the Google Play or Apple store, or
  • Emailing photos with your name, address and mobile number to info@agric.wa.gov.au

 

Contact information

Pest and Disease Information Service (PaDIS)
1800 084 881
Page last updated: Friday, 18 August 2017 - 2:29pm