DISEASE
 
   NAME
     Rust (General)
     Various Rust Species
 
Description
Generally this fungal problem involves many species causing a range of symptoms, but generally produces pustules that release reddish - brown spores. Most fungus is specific to its host and normally will not infect other plant species.

   Pustules

Symptoms
The upper leaf surface develops red, brown or yellow areas and the underside produces bright yellow to orange spores that correspond to the patches above.  Infested leaves become brown in patches, fall prematurely and flower and fruit may also be infected.  This overall, results in a loss of vigour and in small plants may lead to death.  

   Pelargonium x hortorum

Needle Rust (Melampsora farlowii) infects the new leaves turning them to yellow and fall from the shoot giving the branch a scorched appearance. The fruiting bodies are found on the underside of the leaf and is waxy-red.

Rust in Poplar (Melampsora species). A fungal problem involving at least two species (Melampsora medusae) and (Melampsora larici-idaei).
The upper leaf surface becomes flecked with yellow to light green and the underside produces bright yellow orange spores that correspond to the patches above.  Infested leaves become brown in patches, fall prematurely and shoots may die back as a result of not being hardened off to the elements.  This overall, results in a loss of vigour and in small plants may lead to death.  
The source of the fungus is from other infected plants or fallen leaves and is dispersed by wind.
Host plants include Lombardy Poplars particularly Populus nigra ‘Italica’ and cottonwoods.

White Rust (Albugo candida) forms snow white pustules that contain colourless spores that turn yellow then brown and are found on the underside of leaves.

The Rust (Endophyllum sempervivi) affects Sempervivum species by infecting the young leaves and eventually the crown. The mycelium then travels to the roots and extends into any off shots. Leaves that are infected turn yellowish, grow longer and are thin. Persistent infection may kill the plant.

Source and Dispersal
The source of the fungus is from other infected plants or fallen leaves that contain the fruiting bodies and is dispersed by wind.

Favoured Conditions
Generally rust is more prevalent during summer, preferring warm humid conditions and particularly when the leaves are damp.

Affected Plants
A wide range of ornamental annuals, perennials, ferns, trees, shrubs including, Hibiscus species that are infected by Kuehneola malvicola predominantly in southern USA.

Abies species are infected by many types of rust including (Milesia fructuosa) and (Uredinopsis mirabilis).

Abutilon, Phymosia and Alcea species are infected by the rust (Puccinia heterospora).

Alnus species are occasionally infected with Leaf Rust (Melampsoridium hiratsukanum) which forms yellowish pustules on the leaves that develop turning the leaf brown.

Amelanchler species and Calocedrus decurrens are infected by several rust species including (Gymnosporangium libocedri).

Antirrhinum majus (Snapdragon) is infected by the rust (Puccinia antirrhini). This fungal problem that infects the epidermal layer on the leaf underside, forming pale green areas that are raised and split open revealing reddish brown spores that have a dusty appearance.  
As the infestation grows, concentric rings of spore pustules appear around the original infection.  The corresponding position on the upper leafs surface turns yellow eventually causing the leaf to wilt and die.  The infestation is not restricted to the leaves; all above ground parts of the plant are susceptible and infected plants transmit the fungus dispersing it by wind. 
Infected plants should be removed and destroyed.

Anemone and Prunus species are infected by the rust (Tranzschelia pruni-spinosae) that stimulates abnormal growth in the plant during spring.

Aquilegia, Anemone, Delphinium and Clematis species are infected by the Rust (Puccinia rubigo-vera var. agropyri).

Arctostaphylos manzanita is infected by the rust (Pucciniastrum sparsum) occurring in coastal regions but is not normally detrimental to the plant.

Artemisia species are infected by the rust (Uromyces ari-triphylli) which is a systemic disease that is transmitted through seeds. It causes the leaves to turn yellow then die and can infect all parts of the plant except the roots.

Bambusa species are infected by the rust (Dasturella divina) which forms elongated brownish strips on the leaves.

Berberis species may be infected by the Rust (Puccinia graminis) that forms orange spotting on the leaves. It certain regions plants infected with this rust must be removed and destroyed to avoid infecting neighbouring agriculture crops. 

Betula species may be infected by Leaf Rust (Melampsoridium betulinum) that forms reddish-yellow spots on the leaves and heavy infestation can defoliate the tree. The host tree changes to Pseudolarix species during the sexual stage and causes blistering of the leaves.

Calendula species may be infected by the Rust (Puccinia flaveriae).

Callistephus and Solidago species may be infected by the Rust (Coleosporium solidaginis) which forms bright yellow spots particularly on new foliage or young plants.

Canna species may be infected by the rust (Puccinia Thaliae).

   		Canna indica

Centaurea species are infected by the rust (Puccinia cyani) and (Puccinia irrequisita) which can cover the stems and leaves.

Cleome species are infected by the rust (Puccinia aristidae) but rarely requires control.

Dianthus species are infected by the rust (Uromyces dianthi) which forms powdery brown spots that appear on both sides of the leaves. The leaves curl and die and the plant becomes stunted. This is a common problem that occurs when grown in a protected enclosure (hot house). 

Ficus species are infected by the rust (Cerotelium fici) which forms small brown spots, and causes the leaves to turn yellow then fall prematurely.

Fuchsia species are infected with (Pucciniastrum epilobii). This fungus caused purplish red blotches on the upper leaf surface, that become dry in the middle and result in a brown patch with purple edges.  On the underside of the leaf, corresponding to the patches, yellow orange spores form.  Heavily infected leaves become yellow and drop prematurely.  This leads to a loss of vigour in the plant and infected plants transmit the fungus.  
Certain cultivars are more susceptible than others, particularly ‘Orange Drops’ and ‘Novella’.

Hydrangea species is infected by (Pucciniastrum hydrangeae) causing yellowish brown pustules to appear on both sides of the leaf. The leaf becomes dry and brittle.   

		  Rust on Iris species

Iris  and Dietes species are very susceptible to the rust (Puccinia iridis). Leaves form rusty red powdery spots that enlarge. They are appear on both sides of the leaves causing the surrounding area to turn pale yellow then brown and the black spores appear soon after, overwintering on dead infected leaves. Plants may be heavily infected but normally survive attack.

Larix species are infected by several Needle Rusts including (Melampsora paradoxa), (Melampsora medusae) and (Melampsoridium betulinum). The fungi attacks the needles predominantly towards the branch tips turning them yellow and eventually killing them . The underside of the leaf develops pale yellow fruiting bodies.

Lupinus species are infected by three species of rust including (Puccinia andropogonis var onobrychidis).

Malus andChaenomeles species may be infected by the rust (Gymnosporangium juniperi-virginianae) or (Gymnosporangium clavipes) which forms brown or bright orange spots on the leaves or twigs and can defoliate the tree. Juniperus virginiana and Mespilus germanica may also be infected by rust.

Mathiola and Arabis species are infected by White Rust.

Pinus species are infects by the Comandra Blister-rust (Cronartium comandre).

  Plumeria acutifolia

Plumeria species are susceptible to the rust (Coleosporium plumeriae). Leaves and flowers may be infected with the underside forming bright yellow pustules and causes premature leaf or flower drop.

Populus nigra ‘Italica’ is infected by the rust (Melampsora species) which forms pustules to form on the leaves turning them brown and causing premature leaf drop.

Rhododendron and Tsuga species are infected by the rust (Pucciniastrum vaccinii) and is commonly found in nursery stock, spreading rapidly. Tsuga species are also infected by Needle Rust.

Ribes species are infected by the rust (Cronartium ribicola). This leaf rust appears on the underside of the leaves (preferably older leaves) forming dusty brown pustules and is a serious problem. This rust only appears when White Pine (Pinus strobes) grows near where the alternate stage of the fungus occurs.

Rudbeckia species are infected by several species of rust including (Puccinia dioicae) and (Uromyces rudbeckiae).

Salix species are infected by four types of (Melampsora species). 

Senecio, Bellis and Calendula species are infected by the rust (Puccinia lagenophora) which forms blister-like pustules that release brown spores.

Sorbus aucuparia is affected by several rust from the (Gymnosporangium species) causing circular yellow spots, that appear on the leaves during summer and develop into orange cup-shaped fruiting bodies.

Trillium species are infected by the rust (Uromyces halstedii) that damages the leaf surface.

  Festuca arundinacea	  Rust

Turf Grass are susceptible to rust (Puccinia species) and (Uromyces species), causing yellow flecks to appear on the stems and leaves. These markings enlarge before the pustules form and in severs cases the lawn has a yellow, red or brown appearance. 
The infection appears from spring to summer under humid low light conditions and turf that is under stress or with excessive nitrogen in the soil is more susceptible. Many species may be infected including Lolium perenne (Perennial Ryegrass) and Poa pratensis (Kentucky Bluegrass).

                		    Rust on Perennial Ryegrass

Viburnum species are mildly affected by two types of rust (Coleosporium viburni) and (Puccinia linkii).

Viola species are infected by the rust (Puccinia violae) which forms green spots on the underside of the leaves. It is not commonly seen on cultivated plants.

Non-chemical Control
Cut off and destroy any infected branches, fallen leaves and remove heavily infected plants. Improve the culture by, pruning to improve air circulation, allow space between plants and avoid over crowding.  Avoid planting susceptible species.  Plants that are infected with a systemic form should be removed and destroyed

Chemical Control
Not possible to spray large trees but young plants may be treated with a protectant fungicide such as wettable sulphur. In a domestic garden small plants such as Fuchsia species may be sprayed with a protectant chemicals as symptoms appear, aided by the removal of existing infected leaves.  Under commercial conditions stock may be sprayed with a fungicide such as oxycarboxin.
Note
Always read the label for registration details and direction of use prior to application of any chemicals.