Arceuthobium pusillum | |
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Botanical illustration of A. pusillum | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Order: | Santalales |
Family: | Santalaceae |
Genus: | Arceuthobium |
Species: | A. pusillum |
Binomial name | |
Arceuthobium pusillum | |
Range within North America | |
Synonyms | |
Razoumofskya pusilla (Peck) Kuntze |
Arceuthobium pusillum is a perennial, obligate parasitic plant in the sandalwood family. [1] Its common names include Dwarf mistletoe or Eastern dwarf mistletoe. It is one of the most widespread dwarf mistletoes within its range which covers the eastern United States and Canada, from Saskatchewan to Nova Scotia and New Jersey. [2] The species name "pusillum" derives from Latin "pusillus", meaning very small.
This species was first made known to science by Lucy Millington. [3] [4] She wrote in September 1870 to the Torrey Botanical Club explaining that she had found a parasitic plant that she believed to be a mistletoe. [3]
Eastern dwarf mistletoe is a hemiparasitic plant which grows inside the stems of a host plant. Once a seed lands on a branch it will germinate and grow a haustorium which penetrates past the cambium layer and into the host's xylem and phloem tissues; from those tissues it gathers nutrients needed for its own growth and reproduction. [5] Until the mistletoe grows aerial stems it will be completely reliant on the host for all nutrients and energy; even after it grows aerial stems it will still not produce enough energy to support itself and will still be still reliant on the host.
After 2–12 years from the start of the infection, the mistletoe will grow aerial stems outside of the stem it inhabits. These stems are often inconspicuous at 0.5–3 centimetres (0.20–1.18 in). [6] The female stems may be pale yellow green and the male stems may be red or red-brown. Dwarf mistletoe is dioecious, with distinct male and female plants: the male (staminate) flowers are 2mm across and mostly trimerous (having 3 petals or sepals) but may be 2–4-merous. The mature fruits are green, 1.5-3mm sized berries. Seeds ripen in the autumn and the fruits forcefully eject seeds which are coated in a sticky substance that allows them to adhere to whatever they touch. [7] After rain, the sticky seed will slide down a needle that it has landed upon onto a stem where it will then germinate and enter into the host. The seeds may spread long distances via animals.
Eastern dwarf mistletoe parasitizes several genera of conifers including spruces, pines, firs and larches.
The exact species are listed as follows: Abies balsamea (balsam fir), Larix laricina (American larch), Picea abies (common spruce), Picea glauca (white spruce), Picea mariana (black spruce), Picea pungens (blue spruce), Picea rubens (red spruce), Pinus banksiana (jack pine), Pinus resinosa (red pine), Pinus strobus (eastern white pine) [6]
White, black, and red spruces are the most common hosts.
Arceuthobium spp. are considered to be a very serious pest in northern American forests. Unlike the other mistletoes in the Loranthaceae and Viscaceae families, the dwarf mistletoes have very reduced photosynthetic capability and draw heavily on the host for carbohydrates and diminish the amounts of carbohydrates and energy available to the host. The dwarf mistletoe also has a girdling effect on the stem which is infected, meaning that there is an accumulation of sugars distal to the infection which limits the flow of sugars and other chemicals, including hormones, needed by the roots, resulting in dieback of the tree. [6] Due to cytokinins not being transported properly, witches broom may result on the infected trees. The combined effects of dwarf mistletoe distort and suppress the growth of branches and affect the main trunk by causing swellings, knots, or structural weakening. [6]
If a young tree or seedling is infected by the mistletoe, the probability that the tree will die is great. In one study it was determined that 50% of infected seedlings will die over 12 years and the survivors will often be bush-like and not develop properly. [8] In Manitoba Canada, infection by A. pusillum on White spruce reduced the annual radial growth from 6.7mm to 1.4-.4mm.
A. pusillum is considered the most damaging disease in black spruce in the Great Lakes region. Dwarf mistletoe also causes major trunk swellings on red spruce, significantly reducing the value of the lumber; these swellings are not common on black spruce, perhaps due to the fact that black spruce is a much shorter-lived species. [9]
While A. pusillum does not spread rapidly and therefore cannot be considered a highly invasive species, it can build up gradually within a stand of trees and cause severe damage.
A. pusillum is listed as endangered in Connecticut, New Jersey, and Rhode Island as well as threatened in Pennsylvania. [2]
The Douglas fir is an evergreen conifer species in the pine family, Pinaceae. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Oregon pine, and Columbian pine. There are three varieties: coast Douglas-fir, Rocky Mountain Douglas-fir and Mexican Douglas fir.
A spruce is a tree of the genus Picea, a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal (taiga) regions of the Earth. Picea is the sole genus in the subfamily Piceoideae. Spruces are large trees, from about 20–60 m tall when mature, and have whorled branches and conical form. They can be distinguished from other members of the pine family by their needles (leaves), which are four-sided and attached singly to small persistent peg-like structures on the branches, and by their cones, which hang downwards after they are pollinated. The needles are shed when 4–10 years old, leaving the branches rough with the retained pegs. In other similar genera, the branches are fairly smooth.
Picea mariana, the black spruce, is a North American species of spruce tree in the pine family. It is widespread across Canada, found in all 10 provinces and all 3 territories. It is the official tree of the province of Newfoundland and Labrador and is that province's most numerous tree. The range of the black spruce extends into northern parts of the United States: in Alaska, the Great Lakes region, and the upper Northeast. It is a frequent part of the biome known as taiga or boreal forest.
Pinus nigra, the Austrian pine or black pine, is a moderately variable species of pine, occurring across southern Mediterranean Europe from the Iberian Peninsula to the eastern Mediterranean, on the Anatolian peninsula of Turkey, on Corsica and Cyprus, as well as Crimea and in the high mountains of Northwest Africa.
Picea abies, the Norway spruce or European spruce, is a species of spruce native to Northern, Central and Eastern Europe. It has branchlets that typically hang downwards, and the largest cones of any spruce, 9–17 cm long. It is very closely related to the Siberian spruce, which replaces it east of the Ural Mountains, and with which it hybridises freely. The Norway spruce is widely planted for its wood, and is the species used as the main Christmas tree in several countries around the world. It was the first gymnosperm to have its genome sequenced. The Latin specific epithet abies means “fir-like”.
The genus Arceuthobium, commonly called dwarf mistletoes, is a genus of 26 species of parasitic plants that parasitize members of Pinaceae and Cupressaceae in North America, Central America, Asia, Europe, and Africa. Of the 42 species that have been recognized, 39 and 21 of these are endemic to North America and the United States, respectively. They all have very reduced shoots and leaves with the bulk of the plant living under the host's bark. Recently the number of species within the genus has been reduced to 26 as a result of more detailed genetic analysis.
Picea glauca, the white spruce, is a species of spruce native to the northern temperate and boreal forests in North America. Picea glauca was originally native from central Alaska all through the east, across southern/central Canada to the Avalon Peninsula in Newfoundland. It now has become naturalized southward into the far northern United States border states like Montana, Minnesota, Wisconsin, Michigan, Vermont, New Hampshire and Maine; there is also an isolated population in the Black Hills of South Dakota and Wyoming. It is also known as Canadian spruce, skunk spruce, cat spruce, Black Hills spruce, western white spruce, Alberta white spruce, and Porsild spruce.
The plant pathogenic fungus Leucostoma kunzei is the causal agent of Leucostoma canker, a disease of spruce trees found in the Northern Hemisphere, predominantly on Norway spruce and Colorado blue spruce. This disease is one of the most common and detrimental stem diseases of Picea species in the northeastern United States, yet it also affects other coniferous species. Rarely does it kill its host tree; however, the disease does disfigure by killing host branches and causing resin exudation from perennial lesions on branches or trunks.
Arceuthobium americanum is a species of dwarf mistletoe known as American dwarf mistletoe and lodgepole-pine dwarf mistletoe. It is a common plant of western North America where it lives in high elevation pine forests. It is a parasitic plant which lives upon the Lodgepole Pine, particularly the subspecies Pinus contortus ssp. murrayana, the Tamarack Pine. This pine subspecies is most common in the Cascade Range and Sierra Nevada. The American dwarf mistletoe is a yellow-green coral-shaped structure above the surface of the tree's bark, while most of the parasite is beneath the bark. The seeds mature in late summer and disperse to nearby trees. This species has been found to explosively-disperse its seeds through thermogenesis.
Arceuthobium douglasii is a species of dwarf mistletoe known as Douglas fir dwarf mistletoe. It is native to western North America from British Columbia to Texas to California, where it lives in forest and woodland as a parasite. It is found mostly on Douglas fir trees, but occasionally on fir, as well.
Arceuthobium littorum is a species of dwarf mistletoe known as coastal dwarf mistletoe. It is endemic to the coastline of northern California, where it lives as a parasite on Bishop Pine and Monterey Pine trees. This is a dark brown or greenish shrub which is visible as a network of scaly stems extending above the bark of its host tree. Most of the mistletoe is located inside the host tree, attached to it via haustoria, which tap the tree for water and nutrients. The leaves of the mistletoe are reduced to scales on its surface.
Arceuthobium siskiyouense is a species of dwarf mistletoe known as knobcone pine dwarf mistletoe. It is endemic to the Klamath Mountains of northern California and southern Oregon, where it lives as a parasite on knobcone pine trees. This is a brownish shrub which is visible as a network of scaly stems extending above the bark of its host tree. Most of the mistletoe is located inside the host tree, attached to it via haustoria, which tap the tree for water and nutrients. The leaves of the mistletoe are reduced to scales on its surface.
Arceuthobium monticola is a species of dwarf mistletoe known as western white pine dwarf mistletoe. It is endemic to the Klamath Mountains of northern California and southern Oregon, where it lives as a parasite on western white pine trees.
Spruce-pine-fir (SPF) is a classification of lumber that can be traded on commodities exchanges.
Phoradendron tomentosum, the leafy mistletoe, hairy mistletoe or Christmas mistletoe, is a plant parasite. It is characterized by its larger leaves and smaller berries than dwarf mistletoe. Leafy mistletoe seldom kill but they do rob their hosts of moisture and some minerals, causing stress during drought and reducing crop productions on fruit and nut trees. Leafy mistletoe has the ability to photosynthesize on its own but it relies on other plants in order to obtain its nutrients. It attaches itself to a tree and then grows haustoria, in order to get the food and water it needs.
Arceuthobium microcarpum, called the "western spruce dwarf mistletoe," is a parasitic plant known only from Arizona and New Mexico. It is found mostly on spruce trees but also occasionally on Rocky Mountain bristlecone pine. The specific epithet "microcarpum" means "small fruited," in reference to the berries, which are only 3.5 mm long.
Arceuthobium vaginatum, called the "sheathed dwarf mistletoe" or "southwestern dwarf mistletoe" is a parasitic plant found in the southwestern United States and northwestern and central Mexico. It generally is found on pine trees.
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.