Rhizomorph Samples.jpg (IMAGE) University of Utah Caption Armillaria ostoyae is a parasitic fungus with long black tentacles that spread out and attack vegetation. Its cordlike structures called rhizomorphs seek out and attack trees by sucking out their nutrients. They are known to infect and kill over 600 types of woody plants, posing a substantial threat to forests and the agriculture industry. Credit Debora Lyn Porter/University of Utah College of Engineering Usage Restrictions No restrictions. License Public Domain Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.