Rusts are plant diseases caused by pathogenic fungi of the order Pucciniales.
Oomycota forms a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms, called oomycetes. They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction of an oospore is the result of contact between hyphae of male antheridia and female oogonia; these spores can overwinter and are known as resting spores. Asexual reproduction involves the formation of chlamydospores and sporangia, producing motile zoospores. Oomycetes occupy both saprophytic and pathogenic lifestyles, and include some of the most notorious pathogens of plants, causing devastating diseases such as late blight of potato and sudden oak death. One oomycete, the mycoparasite Pythium oligandrum, is used for biocontrol, attacking plant pathogenic fungi. The oomycetes are also often referred to as water molds, although the water-preferring nature which led to that name is not true of most species, which are terrestrial pathogens.
Pinus elliottii, commonly known as slash pine, is a conifer tree native to the Southeastern United States. Slash pine is named after the "slashes" – swampy ground overgrown with trees and bushes – that constitute its habitat. Other common names include swamp pine, yellow slash pine, and southern Florida pine. Slash pine has two different varieties: P. e. var. elliottii and P. e. var. densa. Historically, slash pine has been an important economic timber for naval stores, turpentine, and resin. The wood of slash pine is known for its unusually high strength, especially for a pine. It exceeds many hardwoods and is even comparable to very dense woods such as ironwood.
A basidiospore is a reproductive spore produced by Basidiomycete fungi, a grouping that includes mushrooms, shelf fungi, rusts, and smuts. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are produced by specialized fungal cells called basidia. Typically, four basidiospores develop on appendages from each basidium, of which two are of one strain and the other two of its opposite strain. In gills under a cap of one common species, there exist millions of basidia. Some gilled mushrooms in the order Agaricales have the ability to release billions of spores. The puffball fungus Calvatia gigantea has been calculated to produce about five trillion basidiospores. Most basidiospores are forcibly discharged, and are thus considered ballistospores. These spores serve as the main air dispersal units for the fungi. The spores are released during periods of high humidity and generally have a night-time or pre-dawn peak concentration in the atmosphere.
Cronartium ribicola is a species of rust fungus in the family Cronartiaceae that causes the disease white pine blister rust. Other names include: Rouille vésiculeuse du pin blanc pin (French), white pine Blasenrost (German), moho ampolla del pino blanco (Spanish).
Diplodia tip blight, also known as Sphaeropsis blight, is a widespread disease affecting conifers caused by an opportunistic fungal pathogen, Diplodia sapinea. It is found in “both hemispheres between the latitudes 30° and 50° north and south". The diseases symptoms include: damping off and collar rot of seedlings, stem canker, root disease, and, most commonly, shoot blight. These symptoms have caused significant economic loss to nurseries and pine plantations. In a nursery in the north-central United States, losses of 35% have been reported. Shoot blight and eventual die back can cause a reduction of marketable volume in timber by 63%. Infection of terminal shoots can result in dead-top which significantly limits the usable length of the tree trunk. The presence of the pathogen in concert with severe weather conditions can lead to extreme loss. Following a severe hailstorm in South Africa, nearly 5,000 acres of pine plantation were infected with Diplodia tip blight. It was necessary to prematurely harvest large swaths of the plantations resulting in a loss of 45%. Areas that were not harvested prematurely still suffered an average timber loss of 11%.
Gymnosporangium juniperi-virginianae is a plant pathogen that causes cedar-apple rust. In virtually any location where apples or crabapples (Malus) and Eastern red cedar coexist, cedar apple rust can be a destructive or disfiguring disease on both the apples and cedars. Apples, crabapples, and eastern red cedar are the most common hosts for this disease. Similar diseases can be found on Quince and hawthorn and many species of juniper can substitute for the eastern red cedars.
Uromyces viciae-fabae var. viciae-fabae is a plant pathogen commonly known as faba-bean rust. The rust is distinguished by the typical rust-like marks on the stem and leaves, causing defoliation and loss of photosynthetic surface along with reduction in yield. The disease is fungal and is autoecious meaning it has one plant host. The rust of faba beans is macrocyclic, or contains 5 spores during its life cycle.
Gymnosporangium sabinae is a fungal heteroecious plant pathogen with Juniperus as the primary (telial) host and only Pyrus as secondary (aecial) hosts. It is one of many types of rust fungi affecting plants.
Puccinia pittieriana is a species of rust fungus. It is a plant pathogen which infects agricultural crops such as potato and tomato. Its common names include common potato rust and common potato and tomato rust.
Puccinia monoica is a parasitic rust fungus of the genus Puccinia that inhibits flowering in its host plant and radically transforms host morphology in order to facilitate its own sexual reproduction.
Puccinia horiana is a species of fungus that causes chrysanthemum white rust, is a disease of plant species of the genus Chrysanthemum.
This article summarizes different crops, what common fungal problems they have, and how fungicide should be used in order to mitigate damage and crop loss. This page also covers how specific fungal infections affect crops present in the United States.
Telium, plural telia, are structures produced by rust fungi as part of the reproductive cycle. They are typically yellow or orange drying to brown or black and are exclusively a mechanism for the release of teliospores which are released by wind or water to infect the alternate host in the rust life-cycle. The telial stage provides an overwintering strategy in the life cycle of a parasitic heteroecious fungus by producing teliospores; this occurs on cedar trees. A primary aecial stage is spent parasitizing a separate host plant which is a precursor in the life cycle of heteroecious fungi. Teliospores are released from the telia in the spring. The spores can spread many kilometers through the air, however most are spread near the host plant.
Phragmidium is a genus of rust fungus that typically infects plant species in the family Rosaceae. It is characterised by having stalked teliospores borne on telia each having a row of four or more cells. All species have a caeoma which is a diffuse aecidium lacking a peridium.
Chrysomyxa himalensis, is a species of rust fungi in the Coleosporiaceae family that can be found on Rhododendron and Picea species in the Himalayan region of southern Asia and was introduced in the United States.
Pine-pine gall rust, also known as western gall rust, is a fungal disease of pine trees. It is caused by Endocronartium harknessii, an autoecious, endocyclic, rust fungus that grows in the vascular cambium of the host. The disease is found on pine trees with two or three needles, such as ponderosa pine, jack pine and scots pine. It is very similar to pine-oak gall rust, but its second host is another Pinus species. The fungal infection results in gall formation on branches or trunks of infected hosts. Gall formation is typically not detrimental to old trees, but has been known to kill younger, less stable saplings. Galls can vary from small growths on branch extremities to grapefruit-sized galls on trunks.
Spruce broom rust or yellow witches' broom rust is a fungal plant disease caused by the basidiomycete fungus known as Chrysomyxa arctostaphyli. It occurs exclusively in North America, with the most concentrated outbreaks occurring in northern Arizona and southern Colorado on blue and Engelmann spruce, as well as in Alaska on black and white spruce. This disease alternates its life cycle between two hosts, with the spruce serving as the primary host and bearberry serving as the secondary or alternate host. The name for the disease comes from the distinctive “witches broom”, commonly yellow in color, which forms on the spruce after young needles have been infected. Management must be carried out through physical or mechanical methods, such as the pruning of brooms or the removal of the secondary host from the area, because no chemical control measures have yet been determined to be economically effective. Generally, spruce broom rust is seen as a mostly cosmetic issue, and it is very rarely the direct cause of tree death; however, research has shown a reduction in overall productivity and health of infected trees, making it an important issue for logging and timber companies.
Chrysomyxa weirii, is a fungus that causes a disease, commonly known as Weir's cushion rust, of spruce trees. It is mostly a cosmetic problem, causing yellowish spotting and banding on spruce needles, but in some cases can cause severe premature defoliation. Weir’s cushion rust can also disfigure and reduce growth of spruce trees by targeting the tender needles of newly emerging shoots. This pathogen's spores are spread by wind and water splash and germinate to infect newly developing needles on the same spruce, or neighboring spruce trees. Unlike many other rust disease pathogens, C. weirii is autoecious, only infecting spruce trees. C. weirii is also microcyclic, producing only two of the five possible spore stages common in rust fungi. Trees affected by Weir's cushion rust usually have obvious symptoms, but if treated correctly, the disease can be managed.
Chrysomyxa nagodhii is a species of rust fungus in the family Coleosporiaceae. It was described as new to science by Canadian mycologist Patricia E. Crane in 2001. It probably occurs throughout the range of Ledum decumbens and Rhododendron groenlandicum. On Picea, spermogonia and aecia occur on distinct rusty yellow bands on current-year needles.
