29/06/2018 Update: Citrus Canker response, Northern Territory and Western Australia

Dear Grower,

The nationally coordinated response to citrus canker is progressing, with on-ground response teams in place in the Northern Territory and Western Australia. I am contributing to a number of working groups and committees handling a range of issues related to the response.

There are currently a limited number of infected premises, with nine in the Northern Territory and three in northern Western Australia. The most recent was a pot plant purchased from a known infected premises earlier in the year.

All available evidence indicates that citrus canker is restricted to potted plants in the home and garden sector. Surveillance of citrus production areas so far, has not detected the disease in any citrus orchards.

All infected premises are linked to a single source property in Darwin. We have been able to trace plants that have left this source property, which is providing us with some level of confidence in being able to find potentially infected plants.

Tracing information has been shared with all other jurisdictions, and quick action was taken to follow up on this tracing information, including inspections and thorough diagnostic testing.  As a result of these activities, citrus canker has not been detected in any other mainland states, Tasmania or in the ACT.

A commonwealth lead working group is analysing this trace information to guide the response strategy moving forward.  Plant material shipped from the known infected source premises occurred during the recent wet season or arrived in the east coast prior to the current summer. During this time conditions in the NT and over summer along the east coast (warm and wet) are conducive for citrus canker expression.

Therefore, over the last 12 months suitable conditions would have occurred naturally to allow disease expression if it was present in a consignment of plants. The symptoms of citrus canker are obvious and persistent. Citrus canker forms corky lesions on infected material that will persist. Therefore visual inspection conducted during autumn is considered effective at detecting recent or older infections events.

Symptoms typically express from 7–60 days depending on conditions. Given the time period since plant material has been sent from Darwin, infected plants are expected to have expressed symptoms by now – particularly for retail nursery plants keep under conditions to promote plant growth.

The earliest symptoms on leaves begin at around 9 days post-infection. In ideal research conditions in the field found the shortest time being 6.7 days to disease symptoms in sweet orange, under poor conditions, symptoms may take up to 60 days to appear.

Thorough testing has indicated that this is a new incursion.  We now know that this current incident is not the re-emergence of citrus canker from a previous outbreak.

At 13 June 2018 surveillance has been conducted on 568 premises in the Northern Territory, and 382 in Western Australia. This surveillance has shown infected plants are limited to those supplied from the source property in Darwin. There has been no spread from these infected plants to other host plants.

The other states have also conducted surveillance and testing as a result of the tracing information they received from the NT. In total around plant 7,000 traces have been investigated across Australia, and no canker has been found.

Between the NT and WA, more than 12,000 plants have been destroyed, and disposed of under methods described in PLANTPLAN.

As a precautionary measure, we are asking people with citrus plants to check them for signs of citrus canker. Plants that were purchased within the last 12 months are of particular concern. Photos of citrus canker symptoms and further information can be found at outbreak.gov.au.

I’d encourage you and your staff to take a look at BOLT Website and complete the training.

Please feel free to contact me for explanation or further information.

Yours sincerely,

 

Nathan Hancock

Chief Executive Officer

Citrus Australia Ltd