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Rust symptoms on bridal creeper
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In June 2000 the bridal creeper rust fungus, Puccinia
myrsiphylli, was approved for release as a biocontrol
agent for bridal creeper.
The rust fungus completes its life
cycle on a single host, bridal creeper. It produces five
spore states (rust life cycle)
and infects the leaves and stems of bridal creeper. It obtains
nutrients and water from the plant by establishing intimate
contact with living cells. Through this continuous absorption
or diversion of nutrients, the fungus becomes detrimental
to plant development and reproduction, thereby reducing stem,
fruit, rhizome and tuber production.
The fungus also destroys leaf tissue by producing chlorotic
spots and fruiting bodies that reduce the photosynthetic surface
of the plant. Severely diseased plants shed infected leaves
prematurely and produce few or no fruits. In Australia the
rust fungus first appears on bridal creeper 1-2 months after
the first autumn rains (around May in WA & SA, March in
NSW). From then on, the incidence and severity of the disease
steadily increases during winter to reach its peak in spring
when the plants are flowering and fruiting.
The rust fungus is not systemic which means it does not spread
internally throughout the plant body. Therefore it must reinfect
plants every growing season. The teliospore stage of the lifecycle
can survive adverse conditions (such as summer when there
is no bridal creeper) and ensures that inoculum of the rust
fungus is available for a new disease cycle to be initiated
the following season.
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