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rust,in botany, name for various parasitic fungi of the order Uredinales and for the diseases of plantsdiseases of plants.
Most plant diseases are caused by fungi, bacteria, and viruses. Although the term disease is usually used only for the destruction of live plants, the action of dry rot and the rotting of harvested crops in storage or transport is similar to the rots
..... Click the link for more information. that they cause. Rusts form reddish patches of spores on the host plant. About 7,000 species are known. Some grow entirely on one plant; others require two hosts, plants of two species, in order to complete their life cycles. Cedar rust, for instance, grows on cedar and on apple trees, needing both for development. Blister rust of pine grows on pines and either currant or gooseberry bushes. Black stem rust Puccinia graminis is one of the most destructive to wheat, rye, and other grasses; barberry is an alternate host. A new strain of stem rust identified in 1999 is devastating to even rust-resistant wheat strains. Rusts attack all cereal crops and many fruits, vegetables, forage crops, ornamental plants, and forest trees. Rusts are hard to eradicate; control measures include the use of rust-resistant varieties of seed and the elimination of alternate hosts in agricultural areas. Rusts are classified in the kingdom FungiFungi
, kingdom of heterotrophic single-celled, multinucleated, or multicellular organisms, including yeasts, molds, and mushrooms. The organisms live as parasites, symbionts, or saprobes (see saprophyte).
..... Click the link for more information. , phylum (division) Basidiomycota, order Uredinales.
rust,in chemistry and metallurgy: see corrosioncorrosion,
atmospheric oxidation of metals (see oxidation and reduction). By far the most important form of corrosion is the rusting of iron. Rusting is essentially a process of oxidation in which iron combines with water and oxygen to form rust, the reddish-brown crust that
..... Click the link for more information. .
Plant diseases caused by fungi of the order Uredinales and characterized by the powdery and usually reddish spores produced. There are more than 4000 species of rust fungi. All are obligate parasites (require a living host) in nature, and each species attacks only plants of particular genera or species. Morphologically identical species that attack different host genera are further classified as special forms (formae speciales); for example, Puccinia graminis f. sp. tritici attacks wheat and P. graminis f. sp. hordei attacks barley. Each species or special form can have many physiological races that differ in their ability to attack different cultivars (varieties) of a host species. Rusts are among the most destructive plant diseases. Economically important examples include wheat stem rust, white pine blister rust, and coffee rust. See Uredinales
Rust fungi have complex life cycles, producing up to five different fruiting structures with distinct spore types that appear in a definite sequence. Macrocyclic (long-cycled) rust fungi produce all five spore types, whereas microcyclic (short-cycled) rust fungi produce only teliospores and basidiospores. Some macrocyclic rust fungi complete their life cycle on a single host and are called autoecious, whereas others require two different or alternate hosts and are called heteroecious. See Fungi, Plant pathology
a widespread plant disease caused by fungi of the order Uredinales and characterized by the formation of pustules of various shapes and sizes on the affected organs. A rustlike powder, consisting of fungal spores, can be shaken off the pustules. The disease affects cereals, industrial crops, ornamental plants, forest trees and shrubs, and wild herbs. The causative agents of rust develop on the aboveground parts of plants. They feed only on the contents of living cells and are spread by spores. Diseased plants experience disruptions in metabolism and water balance and a decrease in photosynthesis and growth activity. Rust lowers the quality of fruits and seeds and the baking properties of wheat and rye.
The most harmful rusts are stem rust of cereals (causative agent Puccinia graminis), wheat rust (P. triticina; intermediate plants are meadow rue and Isopyrum), rye rust (P. dispersa; intermediate plants are bugloss and viper’s bugloss), yellow rust of cereals (P. striiformis), dwarf rust of barley (P. hordei; intermediate plant is star-of-Bethlehem), crown rust of oats (P. coronifera; intermediate plant is alder), corn rust (P. sorghi; intermediate plant is sorrel), and sunflower rust (P. helianthi).
Equally harmful are rust of flax (Melampsora lini-usita-tissimi), rust of sugarbeet (Uromyces betae), rust of raspberry (Phragmidium rubi), rust of pear and apple (Gymnosporangium sabinae; intermediate plant is common northern juniper), and rusts of gooseberry and currant (Puccinia ribesii caricis and Cronatrium ribicola, respectively; intermediate plants for both diseases are sedges, Siberian stone pine, and Weymouth pine).
Substantial harm to trees may be caused by pine blister rust (Cronatrium rubicola). Larch needles and birch leaves are harmed by the fungus Melampsoridium betulae, spruce needles by Chrysomyxa ledi (or C. abietis), and pine needles by fungi of the genus Coleosporium.
Control measures include destruction of the intermediate hosts of rust, isolation of plantings from intermediate hosts, and deep plowing of fields to destroy wintering urediospores and teliospores. Through the observance of specific planting times and the application of increased doses of phosphorus and potassium fertilizers, plant resistance to rust can be increased. Sunflower, flax, and sugarbeet seeds should be cleaned, sorted, and disinfected with fungicides. Leaves should be sprayed with fungicides immediately after opening (in the treatment of rust of gooseberry, currant, apple, and pear, as well as rust of pine and spruce needles); spraying should be repeated twice within the next 15 days. The regionalization of plant varieties resistant to certain types of rust is also advisable.
REFERENCESChumakov, A. E. Zashchitapshenitsy ot rzhavchiny. Leningrad, 1964.
Peresypkin, V. F. Sel’skokhoziaistvennaia fitopatologiia. Moscow, 1969.
A. E. CHUMAKOV
What does it mean when you dream about rust?
Anything that develops rust is usually old and no longer in use. In a dream rust may symbolize neglect, lack of care, old age, or a “rusty” skill.