Parasitic Plants

Christina Simokat's letter defended the value of parasitic plants: "Much like wolves and bears, when parasitic plants are in their native environment, they play an essential role ... to increase and preserve diversity" (C&EN, Nov. 27, 2006, page 2). However, Douglas-fir dwarf mistletoe (Arceuthobium douglasii Engelm.) reduces forest timber survival and woodlot property values from southern British Columbia to central Mexico by deforming, stunting, and killing valuable timber resources.

Affected trees eventually form one or more "witches' brooms" that can weigh several hundred pounds, distorting the trees and predisposing them to attack by disease, insects, and periods of drought or other adverse conditions. Severely infested Douglas-fir stands typically have many trees with stunted growth, witches' brooms, dying and dead tops, and dead trees. While parasitic plants like Cuscuta may constitute an "important keystone species" in healthy Southern California chaparral and watershed habitats, mistletoe species are the bane of healthy forests and woodlots in many parts of the country. Montana conifers that have the potential to produce massive centurions are all too often reduced to malformed skeletons and fire tinder.

John Thorne
Somers, Mont.