Eastern dwarf mistletoe

French disease name: Faux-gui de l'est
Pathogen name: Arceuthobium pusillum Peck
Kingdom: Plantae
Class: Santalales
Order: Santalales
Family: Viscaceae

Distribution

From Saskatchewan east

Damage, symptoms and biology

Dwarf mistletoe causes the formation of clumps of swollen and brushy branches, or witches' brooms. This formation of brooms stimulates considerable resin flow that can extend over an area up to three meters in diameter. This parasitic plant produces a sticky seed, which is forcibly ejected onto neighboring trees. The following spring, the seed germinates and produces root-like structures called "sinkers" which penetrate the bark on twigs. These sinkers provide the parasite with nutrients obtained from the host. Two years after germination, aerial shoots form and become visible. The following summer, the plant produces flowers, then seeds and the cycle resumes. Witches' brooms caused by dwarf mistletoe can be distinguished from those associated with the rust pathogen M. caryophyllacearum by the fact that the needles are not shed when dwarf mistletoe is the causal organism, whereas they are shed with rust.

Other information

The male and female plants of Arceuthobium pussilum are generally present on separate branches or host trees. The plant is epiphytic, which means that it lives on trees permanently. Moreover, it is an obligate parasite.