Tree Dwelling Symbionts: Dodder, Lichen, Mistletoe, Moss and Woe-Vine

Summary: A.D. Ali of the Davey Institute identifies, as tree dwelling symbionts to know, epiphytic moss and lichen and parasitic dodder, mistletoe and woe-vine.

Fir dwarf mistletoe (Arceuthobium abietinum) is a parasitic plant; dwarf mistletoe parasitizing white fir (Abies concolor), Lee Canyon, Spring Mountains, southern Nevada; Wednesday, Aug. 10, 2005, 09:34: Stan Shebs, CC BY SA 3.0 Unported, via Wikimedia Commons

Plants are called tree dwelling symbionts when they assume commensal, mutual or parasitic interactions with their hosts, according to Symbiosis of Parasites and Epiphytes in the December 2014 issue of Arborist News.

A.D. Ali of the Davey Institute Division of The Davey Tree Expert Company breaks symbionts into organisms that bring benefits, harm or nothing to their hosts. Commensalism caters to symbionts without causing harm to hosts while mutualism creates benefits for hosts and symbionts and parasitism confers benefits to the detriment of hosts. Dodder, mistletoe and woe-vine deserve to be called parasites since their life cycles draw light, nutrients and resources from hosts whose vigor declines, with fatal consequences.

Ball and Spanish mosses epitomize epiphytes whose commensalism sometimes ends up undesirable to hosts while lichens exemplify epiphytes whose mutualism exists in, and extols, clean ecosystems.

Dodder's red-brown, triangular seeds fling spaghetti-like, yellow-orange stems upward for peg-like organs, called haustoria, to fill parenchyma host, phloem- and xylem-filled tissues within 10-foot (3.05-meter) diameters. The annual grows without chlorophyll, and subsequently without roots or soil, into host tissue while chlorophyll gives perennial, red-orange-tinged yellow-green woe-vine base-to-crown coverage of 80-plus species.

Greater osmotic potential helps American true mistletoe in the eastern and western United States and dwarf mistletoe in the north and west to their hosts' moisture. Dwarf mistletoe impairs host seed production vigor and wood quality and inundates 50-foot (15.24-meter) distances with seeds approaching speeds of 80 feet (24.38 meters) per second.

Dwarf mistletoe and true mistletoe join woe-vine in seed production for wildlife dispersion while ball moss, Spanish moss and dodder juggle seed production for wind dispersion.

Chlorophyll keeps tree dwelling symbionts called epiphytes, airily growing as bromeliads, lichens and orchids upon host phorophytes and independently obtaining moisture, independent photosynthetic producers of nutrients.

Commensal bromeliads such as ball moss and Spanish moss let gray-green leaves and stems respectively bunch atop and drape bark, chain-link fences, poles and power lines. Opened, thinned inner canopies of moisture-, nutrient- and root-stressed trees make ball moss as high-profile as branching Spanish moss stems covered with dense, gray, hair-like trichomes.

Lichen needs commensal interactions when covering, not penetrating, bark and mutualistic interactions when nestling constituent algal producers of photosynthates into constituent fungal providers of dissolved nutrients. It never occasions the management controls that operate against North America's dense growths, wildlife- and wind-dispersed seeding and wet weights of dodder, mistletoe, moss and woe-vine.

Parasitic tree dwelling symbionts such as dodder and woe-vine prompt applications of pre-emergent herbicides, assessments of branch breakage and failure and removal by hand-pulling and pruning.

Dormant foliar applications of ethephon, excision by thinning pruning cuts 12 inches (40.48 centimeters) below infestations and post-excision black polyethylene sheet wraps qualify as mistletoe controls. Severe infestations by dodder, mistletoe and woe-vine require both pests and plants to be cut down and destroyed, rare options for reigning in rampant epiphytic mosses. De-mossing, as mechanical removal of mossy biomasses to pack shipping containers and stuff upholstery, and treatment schedules with copper-based, desiccating, high-pressure sprays serve as moss-managing controls.

Callery 'Bradford' pear, crapemyrtle, eucalyptus, gingko, sweetgum and sycamore tend to thwart mistletoe whereas dodder, mistletoe, moss and woe-vine rarely turn down vacancies on oak trees.

small ballmoss, an epiphyte that forms small ball-like clusters, parasitizes an oak tree (Quercus spp.): Edward L. Barnard/Florida Department of Agriculture and Consumer Services/Bugwood.org, CC BY 3.0 United States, via Forestry Images

Acknowledgment

My special thanks to:
talented artists and photographers/concerned organizations who make their fine images available on the internet;
University of Illinois at Urbana-Champaign for superior on-campus and on-line resources.

Image credits:

Fir dwarf mistletoe (Arceuthobium abietinum) is a parasitic plant; dwarf mistletoe parasitizing white fir (Abies concolor), Lee Canyon, Spring Mountains, southern Nevada; Wednesday, Aug. 10, 2005, 09:34: Stan Shebs, CC BY SA 3.0 Unported, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Arceuthobium_abietinum_1.jpg

small ballmoss, an epiphyte that forms small ball-like clusters, parasitizes an oak tree (Quercus spp.): Edward L. Barnard/Florida Department of Agriculture and Consumer Services/Bugwood.org, CC BY 3.0 United States, via Forestry Images @ http://www.forestryimages.org/browse/detail.cfm?imgnum=4825025

For further information:

Ali, A.D. December 2014. "Symbiosis of Parasites and Epiphytes." Arborist News 23(6): 12-18.
Available @ http://viewer.epaperflip.com/Viewer.aspx?docid=f8826c35-6e05-4e85-9b89-a3ea00f791af#?page=12

Gilman, Ed. 2011. An Illustrated Guide to Pruning. Third Edition. Boston MA: Cengage.

Hayes, Ed. 2001. Evaluating Tree Defects. Revised, Special Edition. Rochester MN: Safe Trees.

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