Rust on Plants and the Organic Gardening methods of Control

Rust

Albugo tragopogonis. Gerbera 'rust' on the underside of a leaf. (Magnified)

Puccinia malvacearum, the Hollyhock (Alcea) rust
Puccinia malvacearum. Hollyhock ( Alcea ) rust on the upper leaf surface.

Puccinia malvacearum, the Hollyhock (Alcea) rust
Puccinia malvacearum. Hollyhock ( Alcea ) rust on the lower leaf surface (magnified).

Phragmidium mucronatum, the Rose (Rosa) rust
Phragmidium mucronatum. Rose ( Rosa ) rust on the underside of a leaf.

Phragmidium mucronatum, the Rose (Rosa) rust
Phragmidium mucronatum. Rose ( Rosa ) rust greatly magnified.

Puccinia antirrhini, the Snapdragon (Antirrhinum) rust
Puccinia antirrhini. Snapdragon ( Antirrhinum ) rust on the lower leaf surface.

The name 'Rust' is a broad title for a fungal disease caused by an extensive group of different fungi. Each form of Rust will only affect species from within a particular plant grouping. The conditions which favour Rust vary with each variety.

Rust is first identifiable with the appearance of small yellow spots on the upper leaf surface. Under the leaf, directly beneath the spots there are powdery blisters containing spores. The millions of spores are distributed by rain/water splash or wind. There are a few beneficial Rusts with one used within the wheat farming community to control skeleton weed.

Common Rusts
Bean Rust
Gerbera ( Gerbera )
Hollyhock ( Alcea )
Rose ( Rosa )
Snapdragon ( Antirrhinum )

Rust is extremely difficult to control. The most effective means is to identify the fungus early and remove affected leaves, including fallen leaf debris. The leaves should be placed in a sealed bag for disposal or burnt. Never place infected debris in the compost bin.

Rust can also be controlled with sulphur, and homemade sprays made from Chamomile, or a blend of Chive, Horseradish, Elder and Casuarina leaves.
Rust resistant strains of some plant species are now available.

	Bean Rust - Uromyces appendiculatus affects beans in cool to warm moist weather. The first sign of rust is the appearance of tiny pale yellow spots on the upper surface of the leaves. Underneath the leaves blisters appear which burst to release the tiny reddish-brown rust spores.
	Gerbera Rust - Albugo tragopogonis can attack Gerberas and is not a true rust. On the upper leaf surface yellow-green spots appear, directly below these on the underside emerge cream coloured blisters containing the fungal spores. The disease is more prevalent in spring and can completely disappear in hot dry weather. Some species of Gerberas are more susceptible than others.
	Hollyhock Rust - Puccinia malvacearum attacks Hollyhocks ( Alcea ). The disease is prevalent in late spring and summer and increases in intensity as the seasons progress. Rust shows on the surface of leaves as yellow-orange spots with reddish centres; on the underside as orange-brown pustules. These can also appear on stems. Older leaves die and fall. As rust fungus overwinters on plant debris, remove and destroy all fallen and infected leaves immediately and cut infected plants to ground level in autumn ( fall ). The common weed, round-leaf mallow ( Malva rotundifolia ) is also affected by the rust and can harbour the disease. Removal of the weed helps in controlling the rust.
	Rose Rust - Phragmidium mucronatum affects Roses ( Rosa ) during hot humid weather. The top surface of a leaf shows the characteristic yellow spots. The spores beneath the leaf resemble a very fine orange dust that turns brown in autumn (fall). Affected leaves fall prematurely. These should be collected and disposed of. Rose rust is not widespread among the species and generally affects only a few of the older varieties. Diced comfrey ( Symphytum officinale ) placed at the base of rose bushes can also assist in keeping rust at bay.
	Snapdragon Rust - Puccinia antirrhini affects Snapdragons ( Antirrhinum ). The disease occurs during cool humid weather. It appears first beneath the leaves as lightish raised spots which later produce very fine reddish-brown spores. Subsequent outbreaks of rust can occur around the original spots. Antirrhinums are available in rust resistant strains.

Puccinia antirrhini, the Snapdragon (Antirrhinum) rust
Puccinia antirrhini. Snapdragon ( Antirrhinum )
rust on the lower leaf surface (magnified).

The WaterWise Garden

Extract from the Colourful WaterWise Gardening
Software

Rust

The WaterWise Garden

Extract from the Colourful WaterWise Gardening Software

Rust

Extract from the Colourful WaterWise Gardening
Software