Arceuthobium Witches' Brooms

All photos were taken by D. L. Nickrent

 Dwarf Mistletoe Species [DLN Coll. No.] Host Species Locality Comments
 A. americanum  Pinus contorta  Buckhorn Mt., Larimer Co., CO  Infection has killed most of the crown of the tree
 A. americanum  Pinus contorta  Myers Gulch, Saguache Co., CO  Large, pendulous, "birds nest" type brooms
 A. americanum [1911]  Pinus contorta  Upper Sky Ranch Rd., CA  Large broom constituting most of the middle portion of this tree
 A. douglasii  Pseudotsuga menziesii  Mt. Herman, El Paso Co., CO  A conspicous "clump"
 A. douglasii  Pseudotsuga menziesii  Santa Fe Co., NM  View upward through a fan-like, systemic broom
 A. douglasii  Pseudotsuga menziesii  Santa Fe Co., NM  View downward through a fan-like, systemic broom. Shoots of the mistletoe visible in the center
 A. pusillum [1956]  Picea glauca  Emmet Co., MI  Dead and heavily broomed spruce trees
 A. pusillum [1956]  Picea glauca  Emmet Co., MI  Large clumpy brooms
A. campylopodum ssp. tsugense   Tsuga mertensiana  Alpine Co., CA  Hemlock showing active and dead nonsystemic brooms
 A. campylopodum ssp. tsugense  Tsuga mertensiana  Mosquito Lake, Alpine Co., CA  Dense, pendulous brooms
 A. campylopodum ssp. tsugense [2677]  Pinus albicaulis  Crater Lake, OR  A dead broom at the bottom of the tree that really looks like *A BROOM* !!
 A. campylopodum ssp. tsugense [2684-86]  Tsuga mertensiana, Abies lasiocarpa, & Pinus albicaulis  Lane Co., OR  Three different host genera, all being broomed by mountain hemlock dwarf mistletoe
A. campylopodum ssp. tsugense [2686]  Pinus albicaulis  Lane Co., OR  A white bark pine with dense, dead broom near base
 A. vaginatum ssp. vaginatum [1981]  Pinus ponderosa var. arizonica  Cerro Potosi, Nuevo Leon, Mexico  Huge clump of mistletoe causing a nonsystemic broom. Note also the persistence and diameter of the branch bearing the DM. Other noninfected branches on the trunk have already self-pruned. Shows hormonal influence of DM on the host tree morphology.
  A. verticilliflorum [1843]  Pinus engelmanii  Durango, Mexico  Similar to above - persistent branch with DM

Last updated: 5-Jan-16 / dln