The mistletoes are seed plants. Their many genera constitute the family Loranthaceae. They are found primarily in the tropics throughout the world. Two genera occur in Europe and two other genera, Phorodendron and Arceuthobium, occur in North America. Species of Phorodendron, or tree thief, are the true mistletoes and are restricted to the Western Hemisphere. They occur primarily on hardwoods but also a few conifers. No serious diseases, from the standpoint of the forester, result except for the disease of the incense cedar. Ornamentals attacked by the true mistletoes are of concern to the homeowner and nurseryman. Our discussion centers on the other mistletoes, the dwarf mistletoes, caused by species of Arceuthobium. These are found exclusively on conifers and in the greatest variety in the American Northwest (Figs. 53-1, 53-2). That they are the most important problem in applied forest pathology in that region attests to their abundance and significance. Spruce and tamarack are attacked but not other eastern conifers by forms of Arceuthobium different from the more destructive western forms. The large stands of beautiful Ponderosa pine in the isolated Black Hills region are free of mistletoes. Continued care should be exercised to preclude their introduction.
KeywordsBotanical Revue Cotyledonary Node Discussion Center Dwarf Mistletoe Aged Stand
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