Dwarf Mistletoe: The Kiss of Death : Biologists Detail Damage Caused by Worldwide Parasite
Delbert Wiens has spent the last 30 years traveling the world in search of mistletoe.
He recently returned from Kenya, Tanzania, Malawi, Zambia, Botswana, Namibia and South Africa, where he spent six months cataloguing various species of mistletoe.
Standing on the north slope of 8,620-foot Mt. Aire, 20 miles east of Salt Lake City, Wiens was examining Douglas fir trees and explaining that the abnormal clumps of twisted, closely clustered shoots and branches are infested with dwarf mistletoe.
No longer than an inch, the mistletoe is sapping the energy from the Douglas firs, said the 53-year-old Wiens, a professor of biology at the University of Utah for 20 years. The strange-looking branching pattern caused by the dwarf mistletoe is called a witches’-broom.
Of all the mistletoe on Earth, dwarf mistletoe does the most damage, devastating entire coniferous forests, Wiens said.
“We are just beginning to grasp the enormity of the damage to the cone-bearing trees--the pine, spruce, hemlock and fir--from dwarf mistletoe,” Wiens noted.
Frank Hawksworth, 60, a forest pathologist specializing in mistletoe, reported that at least 25 million acres of national forest in the United States is infested with dwarf mistletoe.
“Each year 3.1 billion board feet of lumber (valued at $1 per board foot) is lost from dwarf mistletoe infestation,” said Hawksworth, who works at the U.S. Forest Service Rocky Mountain research station at Fort Collins, Colo. “The mistletoe saps the nutrients from the host tree, slurping up water and minerals, weakening the tree and eventually causing its death.”
Hawksworth and Wiens have worked together 24 years, studying the dwarf mistletoe here and in various parts of the world. They are the co-authors of numerous scientific papers and the definitive book on the subject, “The Biology and Classification of Dwarf Mistletoe.”
Both are members of a small group of mistletoers, as they call one another, numbering no more than 200 scientists worldwide.
Mistletoe, a deadly parasite destructive to ornamental, timber, fruit and nut trees, is steeped in ancient legend and lore. Scientists report the plant has been on Earth at least 100 million years.
According to Norse mythology, the god Balder, son of Odin and Frigg, was immune to harm. Knowing this, other gods amused themselves by hurling objects at Balder. But Loki, a god who created discord among his peers, knew that mistletoe could put an end to Balder. So Loki fashioned arrows of mistletoe, fired them at Balder and killed him.
Ancient Druids reportedly cut the hearts out of their victims with knives made of mistletoe. To this day, in many parts of Europe, mistletoe is gathered in midsummer for bonfires, a tradition dating back to the sacrificial ceremonies of the Druids, an order of prophets and sorcerers in ancient Gaul and Britain.
As a parasite, mistletoe is synonymous with evil and death. Yet, ironically, mistletoe is probably best known as the Christmas sprig under which a man is privileged to kiss a woman, a holiday tradition that originated centuries ago in England.
Christmas mistletoe, which in this country is harvested in Texas, New Mexico, Oklahoma and Southern California, is known by the scientific name phoradendron , which, translated from Greek, means the tree thief.
Delbert Wiens grew up in Pomona and did his graduate work in parasitic plants at Claremont Graduate School.
One of Wiens’ colleagues is Roger Polhill of the Royal Botanic Gardens in London, publisher of Golden Bough, a quarterly journal devoted to the study of mistletoe.
Polhill and Wiens have been working together for several years, identifying and cataloguing African mistletoe, and are preparing a book on the subject. Wiens’ study of the African mistletoe is being funded with a five-year, $150,000 grant from the National Science Foundation.
Wiens has been around the world three times tracking down various species of mistletoe in Asia, Africa, Europe, Canada, Mexico, Central and South America, the Pacific Islands, Australia and New Zealand.
