Mistletoes
FIELD GUIDE TO INSECTS AND DISEASES OF ARIZONA AND NEW MEXICO FORESTS
Figure 240a. Figure 240a. Male A. vaginatum subsp. Cryptopdoum
Figure 240b. Figure 240b. Female A. vaginatum subsp. Cryptopdoum

Mistletoes are parasitic plants that slowly weaken and eventually kill their host trees. There are two types of mistletoe in North America, true mistletoe (Phoradendron) and dwarf mistletoe (Arceuthobium). Both are parasitic on the stems of woody plants from which they derive water and mineral nutrients. True mistletoes produce most of their organic nutrients by their own photosynthesis and are believed to obtain little from the host. Although photosynthetic, dwarf mistletoes are dependent on the host for carbon nutrients for growth and reproduction. Dwarf mistletoes are generally considered to be more damaging than true mistletoes; however, host mortality associated with either type of mistletoe infection can occur during periods of drought when lack of stomatal closure of leaves of the parasite causes fatal water loss of the host.