Conks are woody, shelf-like structures produced by some fungi. These fruiting bodies are often seen on trees and can indicate fungal diseases, such as canker rot or butt rot.
Conks are the reproductive form of a large group of fungi known as polypores. Polypores are found in the bark, trunks, and branches of trees, though some are in the soil. Polypores are the primary players in wood decomposition, so their presence often indicates decay. Polypores are important in nutrient cycling, so they aren’t all bad. This group is large and diverse, but they all have conks in common.
The conk clan
This group is defined by how they grow rather than genetics, so it is very diverse. The most common types of conks include:
Also known as bracket fungi, or shelf fungi, this group (Basidiomycota) produces circular, shelf-shaped fruiting bodies that can appear in rows, columns, or singly. Basidiomycetes are the only fungi known to break down lignin. Lignin is what makes trees rigid. The disease that accomplishes this feat is known as white rot.
Some conks are annuals while others are perennials, Some conks can live for 80 years or more. In either case, they tend to be leathery, sturdy growths. These growths produce spores, called basidiospores, in pores found on the underside of the conk.
Conks grow directly out of the wood on which the fungi feed. If you were to cut one open and look at it closely, you would see two layers: a tube layer and a supporting layer. The tubes are honeycomb-like structures lined with a spore-forming surface called the hymenium. The supporting structure creates the shelf and its attachment to the tree.
The problem with conks is that their presence indicates that fungi have taken up residence in your tree. If your tree has conks, the first step is identifying the type. Some fungi are worse than others.
Preventing fungal conks
The fungi that produce conks enter trees through mechanical wounds, damaged roots, broken or rubbing branches, frost cracks, sunburned bark, and improper pruning cuts. Fungal spores travel on the wind, rain, and on birds and insects, so keeping your tree’s protective outer layer intact is the best prevention. The following tips should help with that:
If you have a tree with conks, you should probably contact a certified arborist. They can inspect the tree for structural integrity and to determine the extent of the infection.
Conks may look cool, but you don’t want them on your trees.
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