Complex sentence: Some of these shipments concealed the pathogenic fungus Cryphonectria parasitica, which chokes chestnut trees to death by wedging itself into their trunks and obstructing conduits for water and nutrients.
Split into simpler sentences: Some of these shipments concealed the pathogenic fungus Cryphonectria parasitica. The disease chokes the trees to death by wedging itself into their trunks and obstructing conduits for water and nutrients.