Armillaria ostoyae facts for kids
Quick facts for kids Armillaria ostoyae |
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| Scientific classification | |
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| Armillaria ostoyae | |
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gills on hymenium |
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cap is campanulate or convex |
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hymenium is decurrent |
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stipe has a ring |
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spore print is white |
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ecology is parasitic |
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edibility: choice |
Armillaria ostoyae is a special type of fungus (a mushroom) that can cause disease in trees. It's sometimes called the "Humongous Fungus" because it can grow to be incredibly large! In the western United States, it's a common type of "honey mushroom."
This fungus mostly lives underground. You might not even see it! But in the fall, it grows "honey mushrooms" on the surface. These mushrooms are the parts that produce spores. Because there isn't much competition for space or food underground, this fungus can spread out a lot. It might even cover more land than any other single living thing on Earth!
One amazing example is in Oregon, USA. A huge A. ostoyae specimen in the Malheur National Forest covers about 3.7 square miles (9.6 square kilometers). That's like 2,240 football fields! Scientists think it might be the largest living organism on Earth by weight and area. It could weigh as much as 35,000 tons, which is like 35,000 small cars! Another large one in Michigan covers 91 acres and weighs 440 tons, like 3 blue whales.
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What is Armillaria ostoyae?
This fungus is a type of mushroom that lives on and harms trees. It's found on both hardwood and conifer trees in forests, especially in places like Oregon.
You can often tell Armillaria ostoyae apart from other similar fungi by its look:
- It has creamy-brown colors.
- Its cap (the top part) has noticeable scales.
- It has a clear ring around its stem.
The fungus spreads underground using black, string-like parts called rhizomorphs, which look like "shoestrings." These "shoestrings" help the fungus travel far under the bark of trees or between trees.
How does this fungus grow?
Fungi like Armillaria ostoyae start their lives as tiny spores. These spores are like seeds. They are released into the air by a mature mushroom.
- Armillaria ostoyae spores are white.
- Spores can be carried by the wind or by animals.
- For a spore to grow, it needs to land somewhere suitable and meet another spore of the same species but a different "mating type" (like how some plants need pollen from another plant).
- When two compatible spores meet, they join and start to grow.
- They form dark brown, flat colonies that then produce the "shoestrings" (rhizomorphs). These rhizomorphs help the fungus find food over long distances.
- As the fungus gets more food, it grows into a mature mushroom.
- The mushroom has thin, sheet-like parts called gills under its cap. These gills hold the new spores.
- Once the spores are ready, the mature mushroom releases them, and the cycle starts again!
How big can it get?
Scientists use special tests to study the genes of these fungi. They found that the huge Armillaria ostoyae in Michigan is about 2,500 years old! It started from spores from a parent fungus in Ontario, Canada. Over thousands of years, it grew into the massive size we see today.
The "Humongous Fungus" in Oregon is even bigger. It's thought to be around 8,000 years old! If we count it as one single living thing, it's one of the largest known organisms on Earth by how much area it covers.
Why is it a problem for trees?
This fungus is a big concern for people who manage forests. It can cause serious diseases in many important softwood trees, such as:
- Douglas-fir trees
- True fir trees
- Pine trees
- Western Hemlock trees
Younger conifer trees (around 10 years old or less) are more likely to get sick and die from this fungus. Older trees are usually stronger, but they can still get infected, especially in drier forests.
The fungus spreads mainly through its "shoestring" rhizomorphs. These strings grow into the tree's roots and cause damage.
Where does it live?
Armillaria ostoyae is most common in cooler parts of the northern half of the world. In North America, you can find it on conifer trees in forests in British Columbia and the Pacific Northwest region of the United States. It also grows in parts of Asia.
The "Humongous Fungus" in Oregon is located in the Malheur National Forest. This single fungal colony is the largest known fungal colony in the world!
How do we know a tree is sick?
Forest managers look for certain signs to tell if a tree has this parasitic fungus:
- Sticky sap (resin) flowing from the bottom of the tree.
- The tree's top leaves (crown) looking thin or changing color to yellow or red.
- The tree producing a lot of cones, which can be a sign of stress.
- A white, fan-like growth of fungus under the tree's bark.
- Black "shoestring" rhizomorphs growing on the tree's roots.
- Honey-colored mushrooms growing near the base of the tree in the fall.
- Sick trees often appear in groups or patches.
Sometimes, it can be hard to tell if a tree is sick with A. ostoyae or another fungus called Mottled rot. The main difference is that Mottled rot doesn't have the white fan-like fungal growth under the bark.
How can we help sick trees?
It's tricky to get rid of Armillaria once it's in a tree stump, as it can live there for up to 50 years! Using chemicals isn't usually effective or worth the cost.
The best way to manage this root disease is to:
- Plant different trees: When trees are harvested, foresters can plant new tree species that are more resistant to the fungus. For example, replacing Douglas-fir trees with ponderosa pine or western red cedar can help.
- Remove sick trees and stumps: Another option is to remove diseased stumps and trees using a bulldozer. This helps dry out the fungus and kill it. New trees can then be planted.
- Reduce tree stress: Keeping trees healthy and strong helps them fight off the fungus. This means having a mix of different tree species in the forest and preventing insect problems, which can weaken trees.
Scientists are also looking into using another fungus, Hypholoma fasciculare, to fight Armillaria ostoyae. Early tests show it might be able to compete with Armillaria, but more research is needed.
Can you eat it?
Yes! The mushrooms of Armillaria ostoyae are considered a good edible mushroom.
See also
In Spanish: Hongo de la miel para niños
- Largest organisms
- List of Armillaria species
- List of bioluminescent fungi
