I. Introduction: Quince rust infects fruit, but not leaves, of most apple cultivars. It infects both leaves
and fruit of hawthorn. 'Delicious', which is nearly immune to cedar-apple rust, is highly
susceptible to quince rust.
II. Symptoms: Typically, an infection on apple fruit shows up first as a slightly raised purplish area
on the calyx end of the fruit. On mature fruit, the lesion is sunken and dark green or
purple (photo 2-14). Usually, the entire calyx end of the fruit is involved and the flesh
is deformed to the core. The fungus may produce powdery, fluorescent orange spores in
tube-like structures (aecia) on the calyx end of apple fruit (photo 2-15). Similar
structures are produced on hawthorn leaves and fruit. These spores infect young stems of
the red cedar, resulting in cankers in branches two to five years old (photo 2-16). Spores
produced on these cankers serve as inoculum for apple and hawthorn.
III. Disease Cycle: Basidiospores are produced on
quince rust cankers on the cedar tree and released under conditions similar to those for
cedar-apple rust. Fruit infection occurs only during extended wetting periods when the
blossom is most susceptible, primarily from pink to the petal fall stage. Within a few
weeks after infection, fruit lesions become apparent. In late summer, aecia may form on
infected apple fruit. These produce spores which reinfect young stems on the cedar tree
and initiate cankers which eventually produce the spores that infect apple and hawthorn.
There is no secondary infection by the rust diseases on apple or hawthorn. Although
infected apple fruit may or may not produce aecia, they are commonly produced on leaves
and fruit of infected hawthorn. Thus, quince rust cankers tend to be more prevalent, and
disease potential greater, in areas where hawthorns are growing in proximity to cedars,
such as in pastures adjacent to the orchard. Because quince rust cankers continue to
sporulate for several years, inoculum pressure tends to be more constant from year to year
than for cedar-apple rust, which is influenced by infection conditions during the season
two years earlier.
IV. Monitoring: During the prebloom period and
continuing through fruit set, monitor rust canker maturity on red cedar trees (photo 2-16)
and temperatures during wetting periods. Awareness of wind direction from a large inoculum
source may aid in selection of the most effective fungicide before or after potential
infection periods. At midseason, collect rust cankers (photo 2-16) from red cedar trees
and determine if they are still capable of sporulating by placing them in water in a white
cup. If the water is colored orange after a few hours, the cankers are still capable of
producing spores during future wetting periods. Because there is no secondary infection
within the apple tree, monitoring of the apple tree serves only to pinpoint fungicide
selection or timing weaknesses in the control program. Rust lesions appear on fruit within
two to four weeks after infection.
V. Management: Control measures
applied for cedar-apple rust are effective for quince rust. Some apple cultivars
that are resistant to cedar-apple rust are susceptible to quince rust (e.g. McIntosh and
Delicious), and some cultivars that are susceptible to cedar-apple rust are resistant to
quince rust (e.g. Jonathan).
Chemical control -
Chemical control - home
orchardists (pdf file - Acrobat Reader required)
Text prepared by K.S. Yoder and A.R. Biggs
Download this file in pdf format (Acrobat Reader required)