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FACT
SHEETS>PEST MANAGEMENT>FUCHSIA RUST
Fuchsia Rust
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Rust Pustules on the Bottom of a Fuchsia Leaf
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Introduction
Fuchsia rust is caused by the fungus Pucciniastrum epilobii.
The disease occurs throughout the United States and is common in Massachusetts,
particularly during the winter months. The most serious losses occur during
propagation; however, diseased plants at any stage of growth are unmarketable.
Potted plants may recover from this disease but defoliation significantly
weakens the plants and occasionally results in death.
Symptoms
The disease is first recognized when large circular areas
of chlorosis appear on the upper surface of the leaves. On the underside,
masses of yellow-orange urediospores are produced. As the disease becomes
severe, the spores appear on both sides of the leaves and the circular
spots become less distinct. Occasionally, the spores form along the veins.
Affected leaves may be deformed and defoliation commonly occurs.
Life History
Rust fungi are highly specialized parasites that are dependent
on living plants for growth and development. Most have complex life cycles
that include up to five different spore stages and two different hosts
to complete their life cycle. Pucciniastrum epilobii, the cause
of Fuchsia rust, requires both Abies (fir) and Epilobium
(fireweed) to complete its lifecycle. Fuchsia is related to fireweed and
is also a host of the fungus. The life cycle is as follows. Teliospores,
which allow the fungus to survive the winter, form on infected fireweed
in autumn (teliospores have not been reported on fuchsia). In the spring,
the teliospores germinate and produce basidiospores which infect the needles
of various species of fir (in our region, white and balsam fir). Sexual
conjugation of the fungus occurs on the fir needles followed by the development
and release of aeciospores. The aeciospores can only infect fireweed,
and perhaps fuchsia, but cannot reinfect fir. The fungus then produces
urediospores on infected fireweed and fuchsia. The rusty appearing blisters
on the foliage contain masses of these urediospores. The urediospores
reinfect fireweed and fuchsia repeatedly, but cannot infect fir. The fungus
can reside in the greenhouse, spread, and reinfect fuchsia as long as
infected fuchsia or fireweed are present.
Management
The initial source of spores may be from fireweed or fir.
Stock kept outdoors during the summer may become infected by air-borne
spores. Stock plants brought in from elsewhere may also be a source of
the disease.
Eliminate fireweed in the vicinity of the greenhouse. Fuchsias
that have rust should be discarded or isolated from healthy fuchsias.
Diseased plants can be cut back to the wood, thus reducing the inoculum
in the greenhouse. When plants begin to develop new foliage, it will be
free of rust but a protective fungicide should be applied. Plants should
be spaced to provide good air circulation. Avoid wetting the foliage during
watering.
Fungicides:ethylenebisdithiocarbamate
(Dithane M-45®): 1 ½lb/100 gal (1 lb/100 gal = 1 level Tbs/gal).
There are other formulations that can be used.
The addition of an adjuvant such as Triton B-1956®
to the fungicide will improve performance. Begin
spraying at the first sign of disease and repeat at 7 to 10 day intervals.
Dithane M-45® is compatible with most commonly used agricultural fungicides,
insecticides and growth regulators. Consult a spray compatibility chart
for specific combinations.
Prepared by Dr. Robert L. Wick, Department of Microbiology,
Fernald Hall, Room 111, University of Massachusetts Amherst, MA 01003.
Tel. (413) 545-1045 Fax (413) 545-2532.
March 11, 1992
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