For the white spruce tree (Picea glauca), mistletoe is the kiss of death.
When Barry Logan, an associate professor of biology at Bowdoin College, began studying the interaction between white spruce and the parasitic eastern dwarf mistletoe (Arceuthobium pusillum) 10 years ago, he figured the mistletoe sapped the spruce of food and water until the tree could no longer sustain the drain. “When I entered into this, I mostly thought about the parasite as just a sink for resources,” he says. He soon discovered the system was much more complex. Ten years on, he’s drawing some surprising conclusions about how the petite flowering plant brings down the stately spruce.
Seeking out mistletoe-infected spruce in coastal Maine forests isn’t much of a challenge, Logan says. The parasite causes trees to grow twisted, tangled branches called witches’ brooms. These misshapen branches are dead giveaways that mistletoe is wreaking havoc on the tree’s ...
