Arceuthobium campylopodum subsp. microcarpum

(Engelmann) Nickrent
Phytoneuron 2012-51: 10. 2012.
Common names: Western spruce dwarf mistletoe
Basionym: Arceuthobium douglasii var. microcarpum Engelmann in J. T. Rothrock Rep. U.S. Geogr. Surv., Wheeler, 253. 1879
Synonyms: A. microcarpum (Engelmann) Hawksworth & Wiens
Treatment appears in FNA Volume 12. Treatment on page 432. Mentioned on page 429.

Plants forming witches' brooms. Stems yellowish green, green, orange, red, maroon, or purple, 5(–11) cm; third internode 5–9.3(–16) × 1–1.5(–2) mm, dominant shoot 1.5–3 mm diam. at base. Staminate flowers 2.3 mm diam.; petals 3(–4). Fruits 3.5 × 2 mm.

Phenology: Flowering (Jul–)Aug–Sep; fruiting (Aug–)Sep(–Oct).
Habitat: Coniferous forests, especially with blue or Engelmann spruce.
Elevation: 2400–3200 m.


Meiosis occurs in July, with fruits maturing 12 to 13 months after pollination.

Subspecies microcarpum is a serious pathogen on its principal hosts, Picea engelmannii and P. pungens, as well as on Pinus aristata in northern Arizona. Rare hosts include Abies lasiocarpa and Pinus strobiformis. Interestingly, this mistletoe is not found in the central Rocky Mountains where its principal hosts are most abundant.

Selected References


Lower Taxa


Daniel L. Nickrent +
(Engelmann) Nickrent +
Arceuthobium douglasii var. microcarpum +
Western spruce dwarf mistletoe +
Ariz. +  and N.Mex. +
2400–3200 m. +
Coniferous forests, especially with blue or Engelmann spruce. +
Flowering (Jul–)Aug–Sep +  and fruiting (Aug–)Sep(–Oct). +
Phytoneuron +
A. microcarpum +
Arceuthobium campylopodum subsp. microcarpum +
Arceuthobium campylopodum +
subspecies +