Poster Presentation Science Protecting Plant Health 2017

Bacterial crown rot, a major threat to Australia’s papaya industry (#240)

Nandita Pathania 1 , Fe de la Cueva 2 , Lynton L Vawdrey 1
  1. Queensland Department of Agriculture and Fisheries, Mareeba, Queensland 4880, Australia
  2. University of the Philippines, Los Banos, Laguna, 4031, The Philippines

Bacterial crown rot (BCR) also known as bacterial canker or bacterial decline is considered one of the most important diseases affecting papaya (Carica papaya) and is a serious threat to Australia’s $30 Million papaya industry. Symptoms include angular water-soaked lesions on leaves and petioles causing leaves at the top of the canopy to wilt and die. Firm water-soaked cankers develop on the stem causing the stem to collapse. Small water-soaked lesions which develop on green fruit develop into firm depressed lesions. This disease is reportedly caused by a few species of bacteria from the Enterobacteriaceae family and the genus Erwinia. A research project in the Philippines funded by the Australian Centre for International Agricultural Research (ACIAR) has recently identified the causal agent as E. mallotivora. This bacterium has also been implicated in recent outbreaks of the disease in Malaysia and Tonga with estimated yield losses on the Malaysian Peninsular of 200,000 metric tonnes equivalent to US $58 Million.

Research has shown that high rainfall is the most important weather factor influencing BCR providing conditions necessary for the penetration and distribution of the pathogen. Fifty percent of Australia’s papaya is grown on the wet tropical coast of far north Queensland which has an average annual rainfall of 3750 mm. Consequently an outbreak of BCR would be devastating for the Australian industry.

Research findings continue to enhance our knowledge of bacterial crown rot and improve our awareness and preparedness in the event of such a disease incursion into Queensland. The Australian Quarantine and Inspection Service (AQIS) now restricts the importation of Carica papaya seed from 24 countries where BCR is recorded, with seed being subjected to hot water treatment at 500 C for not less than 20 minutes or growth in post entry quarantine.