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Dwarf Mistletoe (DM) species have been infecting and killing conifer trees
in both the New and the Old World for about 70 million years. They are
the most highly advanced of the world's 42 mistletoe species. Proof of
our own species (Arceuthobium vaginatum ssp. cryptopodum) cohabitating
with Ponderosa pines goes back 10,000 years or more. The problems
caused by DM are nothing new to the West, the Rockies or to Genesee.
What is Dwarf Mistletoe? It is a parasite plant, male or
female, that requires a host, Ponderosa pine, from which it draws water,
nutrients, amino acids, sugars and amines for its own sustenance.
Three to five years will elapse between infection and the outward appearance
of yellowish-orange growths, seven to eight years between infection and seed
production.
During all this time, DM growing and spreading beneath the bark, resulting
in a sever reduction in all growth parameters before death ensues.
Oddly, infected branches often live longer than uninfected branches as the
parasite continues to drain the rest of the tree of its "lifeblood".
The time between infection and death varies tremendously depending on the
vigor of the brooms, climatic conditions and site characteristics (e.g.
available water, slope, aspect, soil element status etc.). Usually, DM
does not actually kill the tree but so severely stresses it that it signals
its weakened condition to Mountain pine beetles that ultimately serve the
coupe de grace.
How Does Dwarf Mistletoe Spread? Primarily it is spread via
seeds that are expelled from the maternal plant at speeds of 60 mph for a
maximum distance of 52 feet or, more typically only 30 feet. Most
seeds, however, are intercepted by the host's needles within 60 to 12 feet
and few escape the crown. Many rain down harmlessly to the ground or
onto smaller pines beneath. The seed is extremely sticky and is easily
carried by birds and occasionally mammals to satellite sites where new
infections are begun on stems of small trunks 5 years of age or more old.
Less than 1/2 percent of each August's seed crop is successful in
germinating that fall and causing new infection.
How Bad is the Problem? Approximately 300 acres are known to be
infected in Genesee from sites as small as a single tree to the largest
comprising 90 acres. Tjos acreage represents more than 25 percent of
Genesee's Ponderosa pine covered lands and directly affects more that 300
residences. Neighboring pines along 1.3 miles of our common borders
are also infected. Most of our infected areas were mapped with
detailed descriptions and prescriptions were provided to us by the Colorado
State Forest Service (CSFS) in 1985. A updated map was completed last
year showing the spread over the past 20 years.
Is There Any Good Associated with Dwarf Mistletoe? At least 11
species of birds and 4 species of mammals utilize Dwarf Mistletoe for food
and / or nesting. Numerous species of moths, butterflies, bugs,
beetles, thrips and mites likewise utilize the parasite. At least 8
species of fungi exclusively parasitize the parasite.
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