Arceuthobium laricis
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fruiting female specimen of Arceuthobium laricis on a larch branch swollen by the infestation |
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| Scientific name | ||||||||||||
| Arceuthobium laricis | ||||||||||||
| ( MEJones ) H.St.John |
Arceuthobium laricis is a species of the genus Arceuthobium in the sandalwood family(Santalaceae). It is a semi-parasite whose host plant is mainly the West American larch ( Larix occidentalis )native towestern North America .
description
As is typical for Arceuthobium species, the plant has very reduced vegetative plant parts and leaves . Most of the plant lives hidden under the bark of the host plant. The visible vegetative parts of the plant are leafless and colored light brown to dark purple; they are 5 to 10 centimeters tall. The vegetative parts of the plant have some chlorophyll and photosynthesis to a small extent; however, the plant is dependent on water and nutrients from the host plant.
Arceuthobium laricis is dioecious separately sexed ( dioecious ), so there are male and female plant specimens. The flowering period is from July to August. Pollination is ensured by insects and the wind. The ripening time of the fruits is about 13 to 14 months from pollination. Each ripe fruit contains only one seed about 2 mm in size; however, several fruits develop simultaneously on the individual shoot. The mature seeds are thrown away from the plant at high speed. Most seeds land about 3 to 5 meters away from the place of origin, but some overcome 13 to 15 meters. A sticky, hygroscopic seed coat causes falling seeds to stick to obstacles. Most of the seeds land on the needles of the host trees. The seed coat acts like a lubricant; the seeds slowly slide off and often remain on the bark at the base of the needle rosette. The seed coat dries and fixes the seed in place; where the seed hibernates. Most of the seeds are lost to insects and fungi, but also to the effects of rain and snow. Only a fraction of the seeds survive the winter and cause a new infection of a host plant. The seeds germinate in early spring. The young root shoots grow along the bark until they meet a possible entry point, usually a needle rosette. Most successful infections occur on one to five year old branches; with older branches, the thicker bark of the host tree already offers better protection. The visible shoots develop two to three years after infection. The life cycle from germination to ejection of the first seeds takes about 4 to 5 years.
distribution
The range of the Arceuthobium laricis is practically identical to that of its main host plant, the West American larch . The deposits are in British Columbia in Canada and in the US states of Oregon , Washington , Idaho and Montana .
ecology
Forest fires are a natural regulator; they can significantly reduce the population of the Arceuthobium laricis . Several species of insects and fungi, including the species Cylindrocarpon gillii, can also harm the parasite.
Systematics
The first valid description comes from the American botanist Harold St. John . The species is also called a form Arceuthobium campylopodum Engelm by some authors . forma laricis (Piper) LS Gill attached to Arceuthobium campylopodum .
Host plants and forestry importance
The preferred host plant of the Arceuthobium laricis is the West American larch . In addition, the mountain hemlock ( Tsuga mertensiana ) is mainly attacked in the Bitterroot Mountains in northern Idaho and in western Montana . The subspecies Pinus contorta subsp. latifolia the pine is often attacked where it grows together with the West American larch. Sometimes Arceuthobium laricis also settles on the rock fir ( Abies lasiocarpa ), the yellow pine ( Pinus ponderosa ) and the purple fir ( Abies amabilis ). The coastal fir ( Abies grandis ), the Engelmann spruce ( Picea engelmannii ), the western Weymouth pine ( Pinus monticola ) and the western hemlock ( Tsuga heterophylla ) are also rarely attacked. The Douglas fir ( Pseudotsuga menziesii ), on the other hand, is immune to attack by Arceuthobium laricis .
This species is considered to be an important forest pest in its area of distribution, causing great economic damage, especially to the forest stands of the West American larch . Infested trees show stunted growth ( witch's broom ), and they are often also attacked by other tree diseases.
Sources and further information
Individual evidence
- ↑ See the entry at GRIN Taxonomy for Plants , the entry at USDA and the entry at ITIS .
- ^ Arceuthobium in the Germplasm Resources Information Network (GRIN), USDA , ARS , National Genetic Resources Program. National Germplasm Resources Laboratory, Beltsville, Maryland. Retrieved August 2, 2017.
literature
- Jerome S. Beatty, Gregory M. Filip, and Robert L. Mathiason: Larch Dwarf Mistletoe . In: Forest Insect & Disease Leaflet . tape 169 , 1997 ( online ).
Web links
- Images at forestryimages.org (engl.)
- Data sheet at www.fs.fed.us (engl.)