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FACTSHEET Exotic Pest Alert: Cedar apple rust Plant Biosecurity Orange Gymnosporangium juniperi-virginianae is an exotic plant pest causing cedar apple rust This disease is a serious threat to Australia’s apple industry If found it must be reported promptly to the Exotic Plant Pest Hotline 1800 084 881 Introduction Cedar apple rust is a fungal disease caused by Gymnosporangium juniperi-virginianae. The cedar apple rust fungus has two hosts. The fungus must spend part of its lifecycle on cedar pine trees (Juniperus virginiana) and part of its lifecycle on apple trees (Malus species). Figure 1 Cedar apple rust gall on the cedar pine stage of the fungus lifecycle Cedar apple rust reduces orchard productivity by defoliating apple trees and blemishing apple fruit. Symptoms On cedar pine trees Small greenish brown swellings appear on the foliage of the cedar pine tree. These galls enlarge, turn a chocolate brown colour and become kidney shaped as they age. In moist weather mature galls sprout orange protrusions called telial horns (Figure 1). The telial horns are made of a gelatinous material that swells so that a gall covered with telial horns may reach 6-8 cm in diameter. Figure 2 Cedar apple rust spots on apple leaves; upper surface (left) lower surface (right) On apple trees This disease first appears on apple leaves as small greenish yellow spots. The spots gradually enlarge and change colour to orange-yellow. Concentric red bands develop around the spots (Figure 2). The types of fungal spores produced in the spots on the upper leaf surfaces differ from those produced from spots on the lower leaf surface. Lesions formed on the underside of the leaf produce hairlike structures which protrude releasing spores. Leaf material thickens around the protrusions making the lesions appear cuplike in shape. These cup shaped lesions can also develop on immature apples. Infected fruit is dwarfed and malformed. August 2012, http://www.dpi.nsw.gov.au/factsheets for updates Primefact 1228 first edition Plant Biosecurity Disease cycle • source propagation material of a known high health status from reputable suppliers The disease cycle of the cedar apple rust fungus is complex. Two very different types of host plants, cedar pine trees and apple trees, are required for the fungus to complete its lifecycle. • monitor your orchard regularly • check your garden junipers for the alternate host spore structures • keep records Cedar pine leaves are infected in summer by spores blown from lesions on apple leaves. Small greenish brown galls appear the following summer but do not enlarge and mature until the following spring. The large galls on the cedar pine are sometimes called “cedar apples”. Reporting If you suspect cedar apple rust: Call the Exotic Plant Pest Hotline on After spring rains occur the galls form gelatinous protrusions. These protrusions (horns) produce spores which are windborne onto apple trees. The fungus establishes on its alternate apple host and completes its lifecycle. 1800 084 881 Build up of the disease within a season in an apple orchard occurs by spores produced on upper surfaces of apple leaves. Visit the Plant Biosecurity website Take photos not samples to minimise the risk of spreading this disease Contact your local district horticulturalist www.dpi.nsw.gov.au/biosecurity/plant Spread Spores are windborne and are spread by prevailing winds within and between apple orchards and to the alternate cedar pine host. Long distance spread is likely to occur through human assisted movement of infected apple or infected cedar pine plant material. Hosts The primary hosts of cedar apple rust are Malus species especially apple (Malus domestica) and crab apple (M. sylvestris). The alternate hosts are members of the genus Juniperus which includes eastern red cedar (J. virginiana) as well as many ornamental junipers. Distribution Cedar apple rust is endemic to North America. An exotic plant pest is a disease causing organism or an invertebrate not present in Australia and which threatens agricultural production, forestry or native and amenity plants. Resources Plant Health Australia Factsheet – Cedar apple rust Oklahoma Cooperative Extension Service EPP-7611 factsheet – Cedar apple rust Figure 1 courtesy of Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org Figure 2 courtesy of E.F. Wicker, USDA, Bugwood.org © State of New South Wales through the Department of Trade and Investment, Regional Infrastructure and Services (NSW Trade & Investment) 2012. You may copy, distribute and otherwise freely deal with this publication for any purpose, provided that you attribute the Department of Trade and Investment, Regional Infrastructure and Services as the owner. ISSN 1832-6668 Actions to minimise risks • practice “Come clean, Go clean” Disclaimer: The information contained in this publication is based on knowledge and understanding at the time of writing (August 2012). 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. • ensure all staff and visitors are instructed in and adhere to your business management hygiene requirements Published by the Department of Primary Industries, a part of the Department of Trade and Investment, Regional Infrastructure and Services. Put in place biosecurity best practice actions to prevent entry, establishment and spread of pests and diseases: PUB12/111 p 2 Exotic Pest Alert: Cedar apple rust