Arceuthobium campylopodum subsp. microcarpum

(Engelmann) Nickrent

Phytoneuron 2012-51: 10. 2012.

Common names: Western spruce dwarf mistletoe
Endemic
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.

Discussion

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

None.

Lower Taxa

None.
Daniel L. Nickrent +
(Engelmann) Nickrent +
Arceuthobium douglasii var. microcarpum +
brown +, orange +, yellow +, olive green +  and yellowish green +
0.3 cm3 mm <br />0.003 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
0.2 cm2 mm <br />0.002 m <br /> (?) +  and 0.3 cm3 mm <br />0.003 m <br /> (?) +
scale-like +
10 cm100 mm <br />0.1 m <br /> (22 cm220 mm <br />0.22 m <br />) +
3 cm30 mm <br />0.03 m <br /> (?) +  and 10 cm100 mm <br />0.1 m <br /> (?) +
Western spruce dwarf mistletoe +
spikelike +
Ariz. +  and N.Mex. +
2400–3200 m. +
globose +  and pyriform +
2.3 cm23 mm <br />0.023 m <br /> (?) +
lenticular +
3.5 cm35 mm <br />0.035 m <br /> (?) +
2 cm20 mm <br />0.02 m <br /> (?) +
Coniferous forests, especially with blue or Engelmann spruce. +
terminal +  and axillary +
bisexual +  and unisexual +
0.93 cm9.3 mm <br />0.0093 m <br /> (1.6 cm16 mm <br />0.016 m <br />) +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
0.1 cm1 mm <br />0.001 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
connate +
scale-like +
pinnate +  and entire +
articulated +
asymmetric +  and symmetric +
yellowish green +
connate +  and distinct +
deltate +  and triangular +
Flowering (Jul–)Aug–Sep +  and fruiting (Aug–)Sep(–Oct). +
2[-3]-carpellate +
Phytoneuron +
mucilaginous +
0.33 cm3.3 mm <br />0.0033 m <br /> (?) +  and 0.55 cm5.5 mm <br />0.0055 m <br /> (?) +
pyriform +  and ellipsoid +
0.23 cm2.3 mm <br />0.0023 m <br /> (?) +  and 0.4 cm4 mm <br />0.004 m <br /> (?) +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
3 +  and 4 +
5 cm50 mm <br />0.05 m <br /> (11 cm110 mm <br />0.11 m <br />) +
purple;maroon;purple;maroon;red;orange;green;yellowish green +
pendulous +  and erect +
fanlike +
5 cm50 mm <br />0.05 m <br /> (?) +
undifferentiated +
A. microcarpum +
Arceuthobium campylopodum subsp. microcarpum +
Arceuthobium campylopodum +
subspecies +
spikelike +
mucilaginous +
evergreen +  and perennial +