In response, the tree sprouts more branches in the area. It accumulates fallen needles and other detritus and can grow nearly impenetrable. Large trees often support dozens of brooms. Unlike leafy mistletoes, the dwarf versions don't produce much of their own food. Over time, dwarf mistletoes often kill their hosts by depleting nutrients or by making them more susceptible to insects.
Dense brooms are also intensely flammable and can increase the severity of forest fires.
And infestations are contagious, as dwarf mistletoe fruits explosively eject sticky seeds that can fly to trees as far as 40 feet away. But in recent years biologists have learned that these unsightly brooms are integral to forest ecology. The amount of red squirrel use we found is outrageous. They'll build their nests on the broom platform, or between the broom and the trunk. They take mushrooms or pine nuts out to brooms and cache them or eat them.