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Cucurbit Bacterial Wilt

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Cucurbit Bacterial Wilt Exotic Pest Alert: Cucurbit bacterial wilt May 2018, Primefact 1649, First edition Rebekah Pierce, Plant Biosecurity & Product Integrity, Orange Cucurbit bacterial wilt (Erwinia tracheiphila) is an exotic plant pest not present in Australia This disease is a serious threat to Australia’s melon industry Figure 1. Symptoms of cucurbit bacterial wilt in If found, promptly report it to the pumpkin Exotic Plant Pest Hotline 1800 084 881 Cucurbit bacterial wilt Cucurbit bacterial wilt is a serious disease affecting a number of commercial species Figure 2. White strings of sap visible when in the plant family Cucurbitaceae. infected runners are cut and pulled apart Curcurbit bacterial wilt is vectored by the Wilting increases in severity until the striped cucumber beetle (Acalymma leaves yellow, wither and die. vittatum) and spotted cucumber beetle Wilt symptoms generally appear 6–7 days (Diabrotica undecimpunctata) which are after infection and the plant is usually not known to occur in Australia. However, completely wilted after two weeks. the ability of Australian insects to vector the disease has not been thoroughly Runners of plants infected with cucurbit explored and may be a possibility. bacterial wilt will show a white, viscous string of sap when runners are cut and Description slowly pulled apart (Figure 2). Cucurbit bacterial wilt symptoms first Damage appear as dull green patches on host plant leaves. These patches wilt in warm weather There is no treatment once plants are and progressively spread to cover the infected with cucurbit bacterial wilt and whole leaf, nearby leaves and eventually the disease will progressively spread the whole plant (Figure 1). throughout the plant. Exotic Pest Alert: Cucurbit bacterial wilt The severity of the disease can vary seasonally. In highly susceptible species cucurbit bacterial wilt has been known to cause nearly complete crop failure. Early season infections result in the highest yield loss. Plants that are still Figure 3. Striped (left) and spotted (right) actively growing at the time of infection cucumber beetles will often die without producing any marketable fruit as fruit produced is of Spread very poor quality. The striped cucumber beetle (Acalymma Lifecycle vittatum) and spotted cucumber beetle (Diabrotica undecimpunctata) are the main Colonies of cucurbit bacterial wilt establish vectors of cucurbit bacterial wilt (Figure 3). and multiply in sap tissues of infected The beetles deposit the bacteria on new plants. Build up of bacteria in the tissues host plant leaves both in sap from their stops the flow of water and nutrients mouthparts and in their fecal matter. The throughout the plant. bacteria require a film of water on the leaf Between seasons it is thought the bacteria surface in order to travel to an open survive either in symptomless host plants wound to infect the plant. or in vector beetles. The beetles transmit Long distance spread of cucurbit bacterial the disease to new hosts when feeding the wilt occurs with the transport of infected following season. plants and vectors carrying the bacteria. Host range Actions to minimise risk Cucurbit bacterial wilt affects plants within Put in place biosecurity best practice the family Cucurbitaceae. Cucumber actions to prevent entry, establishment (Cucumis sativus) and musk melons and spread of pests and diseases: (Cucumis melo) including rockmelon and practice “Come clean, Go clean” honeydew are considered the most susceptible species. ensure all staff and visitors are instructed in and adhere to your Pumpkin and squash (Cucurbita spp.) are business management hygiene considered moderately susceptible. requirements Watermelon (Citrullus lanatus) is relatively source propagation material of a resistant to cucurbit bacterial wilt. known high health status from reputable suppliers Distribution monitor your plants regularly Cucurbit bacterial wilt is found throughout keep records the United States and has been reported from central and northern Europe, South Africa, and Asia. 2 | NSW Department of Primary Industries, August 2018 Exotic Pest Alert: Cucurbit bacterial wilt Reporting Acknowledgements If you suspect cucurbit bacterial wilt: Figure 1 courtesy of Howard F. Schwartz, Colorado State University, Bugwood.org Call the Exotic Plant Pest Hotline on Figure 2 courtesy of M. P. Hoffmann, apsnet.org 1800 084 881 Figure 3 courtesy of (left) Scott Bauer, USDA Email clear photos with a brief Agricultural Research Service, Bugwood.org, and explanation and contact details to (right) Susan Ellis, Bugwood.org [email protected] PUB18/375 An exotic plant pest is a disease causing © State of New South Wales through the Department of Industry, 2018. You may copy, distribute and otherwise organism or an invertebrate not present in freely deal with this publication for any purpose, provided that you attribute the NSW Department of Primary Australia and which threatens agricultural Industries as the owner. production, forestry or native and amenity Disclaimer: The information contained in this publication plants. is based on knowledge and understanding at the time of writing (August 2018). However, because of advances in knowledge, users are reminded of the need to ensure that information upon which they rely is up to date and to check currency of the information with the appropriate officer of the Department of Primary Industries or the user’s independent adviser. 3 | NSW Department of Primary Industries, August 2018 .
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