|Ash bolete, with its eccentric stem partially emerging from the ground - Mark Bower|
|GM sclerotia containing aphids - Mark Brundrett|
|PF aphid - Claude Pilon|
They feed on the ash trees and and can cause significant damage. They also produce honeydew that is the source of food for the GM. In trade, the bolete provides the aphids shelter.
Honeydew is produced by aphids, some scale insects and even the caterpillars of Lycaenidae butterflies. Some species of ants farm aphids, protecting them from harm in exchange for their honeydew. An article in Wikipedia explains, "When their (aphids') mouthpart penetrates the phloem, the sugary, high-pressure liquid is forced out of the gut's terminal opening," an icky fact that doesn't seem to bother the fungus. That gives new meaning to the saying "no guts, no glory."
Exactly how the fungus manages to find the tree and the aphid is unknown but it manages to travel, including to China and Europe, (possibly in an international invasive species exchange program?) As Mark Brundrett pointed out to me while giving permission to use his photograph above, "I think this fungus may become extinct along with its host tree due to ash borer." On the other hand, it might just possibly survive in its invaded lands.
* Fascinating Fungi of the Ozarks, Mark Bower, 2015.