Spruce broom rust

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Spruce broom rust
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Fungi
Division: Basidiomycota
Class: Pucciniomycetes
Order: Pucciniales
Family: Coleosporiaceae
Genus: Chrysomyxa
Species:
C. arctostaphyli
Binomial name
Chrysomyxa arctostaphyli
Synonyms [1]

Peridium coloradense(Dietel) Arth. & F. Kern

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. [2] This disease alternates its life cycle between two hosts, with the spruce serving as the primary host and bearberry (also known as kinnickinnick) serving as the secondary or alternate host. The name for the disease comes from the distinctive “witches broom”, commonly yellow in color, [3] 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 (e.g. fungicides) 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.

Contents

Hosts

Since this pathogen is a heteroecious rust, C. arctostaphyli has a primary and an alternate host upon which it produces different fruiting structures and different spores unique to each structure. As implied in the disease name, spruce broom rust mainly affects four spruce species: white ( Picea glauca ), black ( Picea mariana ) Engelmann ( Picea engelmannii ) and Colorado blue ( Picea pungens ). [4] The alternate host is bearberry, which can be any of three species in the genus Arctostaphylos . [4] This host is also sometimes referred to as kinnikinnick, which is the Native American name for common bearberry (Arctostaphylos uva-ursi), which is in the family Ericaceae . The plant is named for the red edible berries it produces, which are a favorite food of bears when they can get them. They follow a similar life cycle to spruce, as they are both evergreens. [5] There is also another far less common, yet still viable alternate host, manzanita (Arctostaphylos spp.).

Signs and symptoms

Spruce broom rust is named from the so-called “witches brooms” which form as a result of infected needles on the spruce host. The “brooms” are actually needles that were infected from basidiospores from the bearberry alternate host in spring. Twig tissue is typically infected as well, allowing hyphae to spread into an entire branch of needles. In midsummer, bright yellow pustules which make up the broom can be seen. [4] These are actually aecia containing aeciospores for dispersal, making the broom a sign of disease. From afar, there will appear to be a yellowing broom erupting from a portion of a spruce tree. [6] As summer progresses, the aecia (infected needles) will begin to turn brown. In terms of symptoms of spruce broom rust, twigs of the brooms themselves are typically shorter and thicker than normal. Another common symptom is the formation of a canker or gall at the base of the broom. [6] The main damage from the rust is simply overall volume and growth loss. The number of brooms as well as their proximity to the main stem can also play a role in determining the extent of the damage to the tree.

Disease cycle

Chrysomyxa arctostaphyli is an obligate parasite, and as with most other rust fungi diseases, spruce broom rust requires two different host plants to carry out its life cycle and is therefore referred to as heteroecious. [7] The primary or aecial host of the rust is spruce ( Picea spp.), and the secondary or telia host of the rust is bearberry ( Arctostaphylos uva-ursi ). [8] The alternative bearberry host is necessary for aeciospore germination, [9] and is therefore essential for the rust's lifecycle. Spruce broom rust is a macrocyclic rust, meaning that the fungus produces more spore types in addition to teliospores and basidiospores. [10] In midsummer, aecia appear on the epidermis of spruce needles as orange pustules. [11] Eventually, these aecia rupture and release millions of microscopic, orange aeciospores, which are carried to bearberry by wind. [11] These aeciospores are capable of infecting bearberry leaves; however, they are not able to reinfect spruce. [12] Assuming favorable, moist environmental conditions upon the secondary host, these aeciospores germinate and the bearberry's leaves develop dark purple-brown blotches. [11] Come springtime, these blotches develop waxy telia on the bottom of the leaves and pierce the bearberry's epidermis. [11] Teliospores are produced by these telia and germinate to become basidiospores, which infect the primary spruce host when wind carries them to young, developing needles. [11] This infection in the spruce is systemic [13] and perennial, allowing the fungus to live in the brooms from year to year. [8] Upon infection of the developing spruce needles, basidiospores produce haploid mycelia that form spermatia. These spermatia do not infect either host; rather, they serve as male gametes and fertilize receptive hyphae, forming dikaryotic mycelium and in turn dikaryotic aeciospores. [10] From here the disease cycle repeats, and symptoms similar to last season arise on the spruce by midsummer. A feature unique to the Chrysomyxa arctostaphyli disease cycle is the fact that the fungus does not produce urediospores, [11] and thus spruce broom rust is not a truly macrocyclic disease. The lack of urediospores prevents reinfection of the primary host within the same year.

Environment

The intense odor given off from the spermogonia on the needles in the spring attract insects, which cross-fertilize the fungus. [4] This fertilization allows for aecia to form and in turn produce aeciospores. Spruce broom rust is common in the western United States, specifically in the Rocky Mountain Region where it occurs on Colorado blue spruce, and in the boreal forests of Alaska and Canada where it parasitizes both white and black spruce. [2] It was originally thought there was not a connection between bearberry and spruce as hosts, as bearberry had not been documented at such of altitudes of spruce in the Rocky Mountains; it was even initially postulated that the spores found on bearberry were caused by a microcyclic rust which only infected that host and did not have an alternate. [14] However, it was eventually discovered that bearberry could be located in similar altitudes to spruce, and C. arctostaphyli was even found in bearberry at those altitudes. [14] It was then experimentally proved that when bearberry were inoculated in a moist chamber with aeciospores from spruce brooms, telia would begin to form. [14]

Management

In general, spruce broom rust in considered more of a cosmetic issue, and in many cases no serious management measures are required. [15] However, potential economic consequences can be seen in commercial logging areas. In order to manage this, trees with stem cankers or brooms are selectively removed or the brooms are pruned off of the trees. Pruning of brooms is the most effective and economical control option while still reducing the risk of stem breakage and maintaining tree vigor. [16] If the infection occurs on the tree's main bole, the entire top must be removed, including the brooms. [11] Additionally, since both bearberry and spruce must be in the same area for Chrysomyxa arctostaphyli to survive and complete its life cycle, there is the option to remove all bearberry within 1,000 feet of the spruce. [15] Although effective, this route is often hard to accomplish and expensive. A related control measure would be to attempt to reduce moisture around the bearberry in order to prevent secondary infection, but the logistics of this would also be challenging. No chemical measures like fungicides have been found to be effective as of yet, [17] so only the mechanical option of physically removing the brooms to prevent the spread of aeciospores is effective. Since spruce broom rust is mostly cosmetic, infections can potentially be left on the tree to provide habitat for birds and small mammals, which use the large, dense brooms for both resting and nesting. [8]

Importance

Spruce broom rust is an interesting pathogen in terms of its importance in forest management programs. Many spruce trees do not exhibit any symptoms of disease upon infection by Chrysomyxa arctostaphyli, and still many others display effects of a merely cosmetic nature. [12] Besides obviously impacting visual quality, spruce broom rust can also have major, more economically important impacts on timber productivity. Nutrients that were originally sequestered for growth in spruce are redirected to the brooms, which can lead to a reduction in height and radial tree growth. [11] For example, a 1963 US Forest Service study found that trees infected by Chrysomyxa arctostaphyli showed a 30 percent reduction in growth over the course of ten years as compared to healthy trees. [18] The extent of this damage depends on the number and size of brooms, as well as their location. [19] When brooms occur upon the primary bole of the spruce, this can lead to a phenomenon known as top kill, in which the portion of the spruce above the brooms dies. [12] As the infection continues to grow and more sections of the tree die, new entrance ways open up for wood decaying fungi, such as red ring rot ( Phellinus pini ). [20] These fungi are capable of devastating the volume of usable wood obtained from spruce trees, and in turn greatly reducing the trees’ marketable value, [20] because they are highly specialized in removing the wood's structural compounds. [12] Additionally, this internal wood decay causes spruce trees to become structurally unstable, posing relevant hazards in residential and recreational areas. [12] Finally, although tree death is not common in infected trees, Chrysomyxa arctostaphyli may weaken the spruce and cause it to become highly vulnerable to other potential killers such as other fungi, bark beetles, or simply by increasing the tree's susceptibility to intense wind, water, and snow. [12] The same 1963 US Forest Service study found that infected trees had a three times greater mortality rate over a ten-year period than healthy trees. [18] Nevertheless, Chrysomyxa arctostaphyli may indeed play an ecologically vital role in the Yukon. Oftentimes squirrels, fishers, and other forest animals utilize cavities within brooms, especially those carved out by other wood decaying fungi, as sources of shelter and dens. [21]

Related Research Articles

<span class="mw-page-title-main">Basidiomycota</span> Division of fungi

Basidiomycota is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basidiomycota includes these groups: agarics, puffballs, stinkhorns, bracket fungi, other polypores, jelly fungi, boletes, chanterelles, earth stars, smuts, bunts, rusts, mirror yeasts, and Cryptococcus, the human pathogenic yeast. Basidiomycota are filamentous fungi composed of hyphae and reproduce sexually via the formation of specialized club-shaped end cells called basidia that normally bear external meiospores. These specialized spores are called basidiospores. However, some Basidiomycota are obligate asexual reproducers. Basidiomycota that reproduce asexually can typically be recognized as members of this division by gross similarity to others, by the formation of a distinctive anatomical feature, cell wall components, and definitively by phylogenetic molecular analysis of DNA sequence data.

<span class="mw-page-title-main">Rust (fungus)</span> Order of fungi

Rusts are fungal plant pathogens of the order Pucciniales causing plant fungal diseases.

<i>Cronartium ribicola</i> Species of rust fungus

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).

<span class="mw-page-title-main">Teliospore</span>

Teliospore is the thick-walled resting spore of some fungi, from which the basidium arises.

<i>Gymnosporangium globosum</i> Species of fungus

Gymnosporangium globosum is a fungal plant pathogen that causes cedar-hawthorn rust.

<i>Gymnosporangium juniperi-virginianae</i> Species of fungus

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.

Puccinia schedonnardii is a basidiomycete fungus that affects cotton. More commonly known as a “rust,” this pathogen typically affects cotton leaves, which can decrease the quality of the boll at time of harvest. As large percentages of cotton in the United States are resistant to various rust varieties, there is little economic importance to this disease. In places where rust is prevalent, however, growers could see up to a 50% reduction in yield due to rust infection.

<i>Puccinia coronata</i> Species of fungus

Puccinia coronata is a plant pathogen and causal agent of oat and barley crown rust. The pathogen occurs worldwide, infecting both wild and cultivated oats. Crown rust poses a threat to barley production, because the first infections in barley occur early in the season from local inoculum. Crown rusts have evolved many different physiological races within different species in response to host resistance. Each pathogenic race can attack a specific line of plants within the species typical host. For example, there are over 290 races of P. coronata. Crops with resistant phenotypes are often released, but within a few years virulent races have arisen and P. coronata can infect them.

<i>Puccinia menthae</i> Species of fungus

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<i>Uromyces viciae-fabae <span style="font-style:normal;">var.</span> viciae-fabae</i> Species of fungus

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.

Naohidemyces vaccinii is a plant pathogen that affects members of the Vaccinium and Tsuga genera, causing leaf rust on lingonberries, blueberries, and cranberries, and early needle cast on hemlocks. Naohidemyces vaccinii is found on the Vaccinium genus in Canada, the United States, the United Kingdom, Europe, Russia, China, Korea, and Japan, and on hemlock in AK, ID, WA in the United States, BC in Canada, and Japan.

<i>Gymnosporangium sabinae</i> Species of fungus

Gymnosporangium sabinae is a species of rust fungus in the subdivision Pucciniomycotina. Known as pear rust, European pear rust, or pear trellis rust, it is a heteroecious plant pathogen with Juniperus sabina as the main primary (telial) host and Pyrus communis as the main secondary (aecial) host.

<i>Puccinia monoica</i> Species of fungus

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.

<span class="mw-page-title-main">Telium</span> Structure produced by rust fungi as part of the reproductive cycle

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.

<span class="mw-page-title-main">Pine-pine gall rust</span> Fungal disease of pine trees

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.

<i>Chrysomyxa weirii</i> Species of fungus

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.

Phakopsora euvitis is a rust fungus that causes disease of grape leaves. This rust fungus has been seen in regions including: Eastern Asia, Southern Asia, Southwestern Brazil, the Americas, and northern Australia. It is widely distributed in eastern and southern Asia but was first discovered on grapevines in Darwin, Australia in 2001 and was identified as Asian grapevine leaf rust by July 2007.

Melampsora amygdalinae is a fungal pathogen and part of the division Basidiomycota. It is known as a rust fungus that is host specific. M. amygdalinae commonly infects willows of the genus Salix. This fungus was first discovered in 1909 by Heinrich Klebahn who was a professor of soil biology in Hamburg. Neimi at el. explain how the pathogen occurs throughout the whole distribution of the host, and the small natural populations are an area of interest. This rust fungus is annual and autoecious, which references the fungus spending its entire life in a single host.

<i>Cronartium quercuum</i> Fungal disease of pine and oak trees

Cronartium quercuum, also known as pine-oak gall rust is a fungal disease of pine and oak trees. Similar to pine-pine gall rust, this disease is found on pine trees but its second host is an oak tree rather than another pine.

References

  1. ↑ "Chrysomyxa arctostaphyli". Natural Resources Canada . Retrieved June 17, 2013.
  2. 1 2 Peterson, Roger S. Effects of Broom Rusts on Spruce and Fir. Vol. 7. Ogden, Utah, Intermountain Forest & Range Experiment Station: Forest Service, U.S. Dept. of Agriculture, 1963.
  3. ↑ Klingström, A., and G. Lundeberg. "Control of Lophodermium and Phacidium needle cast and Scleroderris canker in Pinus silvestris." European Journal of Forest Pathology 8.1 (1978): 20-25.
  4. 1 2 3 4 Broom Rusts of Spruce and Fir. US Forest Service Dept. of Agriculture: Rocky Mountain Region.
  5. ↑ Cameron, Ward (2005). Mountain Nature Field Guide.
  6. 1 2 John Schwandt (2006). Management Guide for Spruce Broom Rust. USDA, US Forest Service Dept. of Agriculture.
  7. ↑ Ziller, Wolf G. "Studies of western tree rusts. VIII. Inoculation experiments with conifer needle rusts (Melampsoraceae)." Canadian Journal of Botany 48.8 (1970): 1471-1476.
  8. 1 2 3 Ferguson, Brennan A. "Broom Rusts." Idaho.gov/forestry. Idaho Department of Lands, Sept. 2014. Web. 11 Nov. 2014.
  9. ↑ Krebill, G. (1969). Germination of Aeciospores of Chrysomyxa Arctostaphyli. Phytopathology, Vol. 59, No. 1 (Jan. 1969), pp. 13.
  10. 1 2 Agrios, George. (Dec. 2004). Plant Pathology. 5th Edition, pp. 564-565.
  11. 1 2 3 4 5 6 7 8 "Spruce Broom Rust." Yukon Forest Health. Yukon Energy, Mines and Resources Forest Management Branch, Government of Yukon. Web. 11 Nov. 2014.
  12. 1 2 3 4 5 6 Forest Service Leaflet. "Spruce Broom Rust." Region 10 - State. USDA Forest Service, Aug. 2001. Web. 11 Nov. 2014.
  13. ↑ Wood, A. R. "Infection of Chrysanthemoides monilifera ssp. monilifera by the rust fungus Endophyllum osteospermi is associated with a reduction in vegetative growth and reproduction." Australasian Plant Pathology 31.4 (2002): 409-415.
  14. 1 2 3 Peterson, R. S. (1961). Notes on Western Rust Fungi I. Chrysomyxa. Mycologia, Vol. 53, No. 4 (Jul.-Aug., 1961), pp. 427-431. https://www.jstor.org/stable/3756585
  15. 1 2 "Spruce Needle Rust." : Yard and Garden : Garden : University of Minnesota Extension. University of Minnesota Extension. Web. 11 Nov. 2014.
  16. ↑ "Broom Rusts of Spruce and Fir." Forest Health Protection-Rocky Mountain Region. United States Department of Agriculture, 2011. Web. 11 Nov. 2014.
  17. ↑ "Spruce Broom Rust (Chrysomyxa Arcostaphyli)." Plantwise Knowledge Bank. Plantwise. Web. 11 Nov. 2014.
  18. 1 2 Peterson, Roger S. "Effects of broom rusts on Spruce and Fir." Research Papers. US Forest Serv. (1963).
  19. ↑ Schwandt, John. "Management Guide for Spruce Broom Rust." Forest Health Protection and State Forestry Organizations. United States Forest Service, Jan. 2006. Web. 11 Nov. 2014.
  20. 1 2 Paragi, Thomas F. "Density and Size of Snags, Tree Cavities, and Spruce Rust Brooms in Alaska Boreal Forest." Western Journal of Applied Forestry 25.2 (2010): 88-95.
  21. ↑ Weir, Richard D., and Pedro Lara Almuedo. "British Columbia's Interior: Fisher Wildlife Habitat Decision Aid." Journal of Ecosystems and Management 10.3 (2010).
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