Witches' Broom Formation in Conifers Infected by Arceuthobium spp.: An Example of Parasitic Impact upon Community Dynamics

The differential effects of dwarf mistletoe infection and broom abundance on the radial growth of managed ponderosa pine

“…Brooms alter the structure and dynamics of infested stands (Tinnin, 1984;Mathiasen, 1996;Godfree et al, 2003) and enhance habitat diversity for other plants and animals (Tinnin et al, 1982;Castello et al, 1995;Bennets et al, 1996;Hedwall, 2000). The effects of mistletoe on tree growth are well described (see Hawksworth and Wiens, 1996), yet the literature addressing the process of broom formation and the impacts of brooming on tree growth is meager.…”

Callus Culture of Arceuthobium americanum Nutt. ex Englem. and Explant Response to Varying Auxin and Cytokinin Concentrations

“…When Arceuthobium americanum infects lodgepole pine, it induces the formation of witches' brooms (Tinnin et al 1982, Brandt et al 2005. Additionally, Schaffer et al (1983) have shown that witch's broom formation in ponderosa pine (Pinus ponderosa Dougl.…”

Disturbance Agents and Their Associated Effects on the Health of Interior Douglas-Fir Forests in the Central Rocky Mountains

“…Spread rates of Douglas-fir dwarf mistletoe are often accelerated in multi-storied Douglas-fir stands where understory trees receive abundant seed rain from infected overstory trees, as reported in southwestern interior Douglas-fir stands [184]. When Douglas-fir is the climax member of the community, as often is the case in interior Douglas-fir stands, there is typically not a shortage of hosts for Douglas-fir dwarf mistletoe, which can persist unless a severe disturbance leads to the loss of its host species [181]. Seedlings and saplings, especially those with main stem infections, readily succumb to this parasite [186].…”

“…Although dwarf mistletoes are capable of complete photosynthesis, upwards of 60% of their carbohydrates can be extracted from their hosts [179]. Tree response to infection results in dense abnormal growth of host twigs that form branch clusters termed witches' brooms [181]. This irregular growth pattern changes branch structure, function, and can eliminate cone production by infected branches [182,183].…”

“…This irregular growth pattern changes branch structure, function, and can eliminate cone production by infected branches [182,183]. Additional degenerative, induced effects on host plants include stem and height growth reductions, top kill, and reduced forest productivity [181,184]. Douglas-fir dwarf mistletoe is the most damaging species that parasitizes Douglas-fir [174,185].…”