Download Exotic Pest Alert: Cedar apple rust

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