Armillaria ostoyae is one of the toughest tree-killing fungi on the planet. It assembles with black tentacle-like structures called rhizomorphs, which leach onto trees and suck out their nutrients.

The reason the fungi is so hard to kill has previously baffled scientists, with farmers hacking away at the rhizomorphs only to find them growing back quickly. Thankfully, a team of engineers from the University of Utah has cracked the case behind one of the secrets to its resilience.

Targeting the tentacles

Previously, work in the field has focussed on the fungi’s life cycle, interactions with the environment, and methods of control, which has not yielded any successful results. Therefore, the team led by Steven Naleway honed in on a different area: the biomechanical structure of the rhizomorphs.

The team found a melanized layer on the outside of the black chords, acting as protection from chemical and mechanical intrusion. “This outer layer is pretty tough,” stated Naleway. “It’s kind of like a tough plastic. For the natural world, it is quite strong.”

The research, published in Journal of the Mechanical Behavior of Biomedical Materials, discussed new key information regarding the formation of this strong layer. As you move further from the surface, rhizomorphs are seen to be more porous. This allows for protection and also absorbance of the tree’s nutrients deeper into the plant. Another key feature is the calcium content of the fungi, this is what allows it to resist acidic chemical and insect attacks.

Save the trees

This terrifying fungus can victimize 600 types of woody plants, killing them off within several years. The fungus poses a threat to forests and the agricultural industry, costing $1.5 million in damages to Georgia’s peach trees between 2000-2002.

Therefore, methods to combat the organism are much needed. “If you’re going to have some kind of human biocontrol, you need to combat this calcium and better penetrate this outer surface,” said Naleway. The team hope with this new information farmers, pest control developers, and forestry officials can create more effective methods to clamp down on Armillaria ostoyae infections.

Source study: Journal of the Mechanical Behavior of Biomedical Materials – The melanized layer of Armillaria ostoyae rhizomorphs: Its protective role and functions