Posts Tagged: Armillaria
Oak Root Fungus - Armillaria mellea
The fungal disease “oak root rot” (Armillaria mellea) has evolved with California oaks...
Is It a Toadstool or a Mushroom?
By Penny Pawl, UC Master Gardener of Napa County Occasionally you may see things sprouting around...
Fungi in lawn. (UC IPM)
Fascinated by Fungi, Gordon Walker. (gordonwalkerconsulting.com)
Bark compost with fungi. (backyardgardenlover.com)
Armillaria mellea. (antropocene.it)
Armillaria tabescens. (ultimate-mushroom.com)
Armillaria at tree roots. (mykowebcom)
Mushrooms in lawn. (bobvila.com)
Fungi on tree. When this is on the outside, the fungi is deep inside the tree. (ucanr.edu)
Slime mold 1. (lancaster.unl.edu)
Slime mold 2. (extension.umaine.edu)
Toadstools and Mushrooms. (neilsperry.com)
Armillaria Root Rot in Landscape Trees
What is Armillaria Root Rot? Armillaria root rot is a severe fungal disease that affects trees,...
Help!! My Japanese Maple is Dying Back!!
Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Client's Request: My 20 year old Japanese maple (Acer spp) did not return this year. I need help identifying what the problem is and how to resolve it. Pictures below show mushroom looking things growing on the tree. Not sure if it's the cause of the dieback. Thank you in advance!
![Japanese Maple (Acer spp) w/ Japanese Maple (Acer spp) w/](http://ucanr.edu/blogs/ccmgblog/blogfiles/51791.jpg)
MGCC Help Desk Response: As you have already recognized, the presence of the mushrooms on the trunk of your Japanese Maple tree is not a good development. It indicates that a fungus has somehow entered the tree. Typically, such fungi enter a tree's system either through the roots or through a wound on the tree or its roots. Wounds can be caused by such things as a nick by a lawn mower or “weed eater” cutter, excavations or poor pruning practices. Fungi can also enter the tree if a “root rot” disease develops. Once the fungus has entered the tree's interior tissue, it breaks down wood fibers, releasing nutrients needed to feed the fungus. After mushrooms become visible, the attack is well underway, and the fungus has begun reproducing through spores in or on the mushrooms.
When mushrooms are present on the main trunk of the tree as appears to be the case with your tree, there is not much hope that the tree can be saved. The breakdown of the tree's internal wood fibers to feed the fungus may weaken the tree structurally and if the problems has developed from a root rot problem, the roots may be weak and less able to support the tree. For these reasons, you may want to consider removing the tree.
Without knowing more about the history of your tree and the symptoms of earlier declines to the tree's health that may have been evident in prior growing seasons, we are unable to determine the precise cause of the decline of your tree. You may be able to learn more about the possible causes of the tree's decline at this University of California website: http://ipm.ucanr.edu/PMG/GARDEN/PLANTS/maple.html The website lists common disease problems that can affect Japanese Maple. We suggest that you look at the links for “root and crown rot” and for “wood decay” and consider whether they describe earlier signs or symptoms of a problem that you may have noticed in past growing seasons.
The abundance of pale, honey colored mushrooms shown in your photos suggest another possible fungal root disease not mentioned on the UC website referenced above. A fungus known as Armillaria mellea is the cause of Armillaria root rot. Early symptoms you might have observed if this fungi is the cause of the problem include reduced growth, yellowish leaves and dieback of twigs and branches. The development of the pale colored mushrooms around the base of the tree or the surrounding ground is a later development in the progress of the disease. If you suspect this fungus might be the cause of the tree's decline, you may want to try to confirm the diagnosis by looking for the presence of white mycelial fans between the bark and the underlying sapwood of the tree. This UC website has additional information about Armillaria root rot and includes a photo showing the white mycelial fan structures that underlie the bark: http://ipm.ucanr.edu/PMG/GARDEN/PLANTS/DISEASES/armillariartrot.html
Keep in mind that if the source of the fungal disease was in your soil, the fungal spores may remain in the soil and could potentially affect the roots of a replacement soil. For this reason, it would be a good idea to try to determine what disease was present in your tree. You might want to consider hiring an arborist to examine the tree and confirm what caused the problem. The arborist might also be able to provide a crew to remove the tree and give you some guidance on steps to take to avoid having a replacement tree develop the same problems. Here is a link to the International Society of Arboriculture (ISA) website. It has a search feature that allows you to find a certified arborist based on where you live. https://www.treesaregood.org/findanarborist
I hope that you find this information to be helpful. Please contact us again if you have further questions.
UC Master Gardener Program of Contra Costa County (tkl)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer our gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523, although we will be moving this spring. We will notify you if/when that occurs. We can also be reached via telephone: (925)646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (//ucanr.edu/blogs/CCMGBlog/)
/table>Oil and Fungal Evolution?
Like most of us, trees don't want to be eaten alive.
To prevent this gruesome fate, they developed extremely tough cell walls around 400 million years ago. For millions of years, nothing could break down lignin, the strongest substance in those cell walls. When a tree died, it just sank into the swamp where it grew. When the fossil record started showing trees breaking down around 300 million years ago, most scientists assumed it was because the ubiquitous swamps of the time were drying up.
But biologist David Hibbett at Clark University suspected that wasn't the whole story. An alternative theory from researcher Jennifer Robinson intrigued him. She theorized that instead of ecosystem change alone, something else played a major role - something evolving the ability to break down lignin. Through evolutionary biology research supported by the Department of Energy's (DOE) Office of Science, Hibbett and his team confirmed her theory. They found that, just as she predicted, a group of fungi known as "white rot fungi" evolved the ability to break down lignin approximately the same time that coal formation drastically decreased. His research illustrated just how essential white rot fungi were to Earth's evolution.
Fungi are still indispensable. The short-order cooks of the natural world, they have an unheralded job making nutrients accessible to the rest of us. Just like cooking spinach makes it easier to digest, some fungi can break down plant cell walls, including lignin. That makes it easier for other organisms to use the carbon that is in those cell walls.
"We all live in the digestive tract of fungi," said Scott Baker, a biologist at DOE's Pacific Northwest National Laboratory. If we weren't surrounded by fungi that decay dead plant material, it would be much harder for plants to obtain the nutrients they need.
To understand fungi's role in the ecosystem and support biofuels research, scientists supported by DOE's Office of Science are studying how fungi have evolved to decompose wood and other plants.
The Special Skills of Fungi
Fungi face a tough task. Trees' cell walls contain lignin, which holds up trees and helps them resist rotting. Without lignin, California redwoods and Amazonian kapoks wouldn't be able to soar hundreds of feet into the air. Trees' cell walls also include cellulose, a similar compound that is more easily digested but still difficult to break down into simple sugars.
By co-evolving with trees, fungi managed to get around those defenses. Fungi are the only major organism that can break down or significantly modify lignin. They're also much better at breaking down cellulose than most other organisms.
In fact, fungi are even better at it than people and the machines we've developed. The bioenergy industry can't yet efficiently and affordably break down lignin, which is needed to transform non-food plants such as poplar trees into biofuels. Most current industrial processes burn the lignin or treat it with expensive and inefficient chemicals. Learning how fungi break down lignin and cellulose could make these processes more affordable and sustainable.
Tracing the Fungal Family Tree
While fungi live almost everywhere on Earth, advances in genetic and protein analysis now allow us to see how these short-order cooks work in their kitchen. Scientists can sample a fungus in the wild and analyze its genetic makeup in the laboratory.
By comparing genes in different types of fungi and how those fungi are evolutionarily related to each other, scientists can trace which genes fungi have gained or lost over time. They can also examine which genes an individual fungus has turned "on" or "off" at any one time.
By identifying a fungus's genes and the proteins it produces, scientists can match up which genes code for which proteins. A number of projects seeking to do this tap the resources of the Joint Genome Institute (JGI) and the Environmental Molecular Sciences Laboratory (EMSL), both Office of Science user facilities.
Understanding the Rot
Just as different chefs use different techniques, fungi have a variety of ways to break down lignin, cellulose, and other parts of wood's cell walls.
White Rot
Although fungi appeared millions of years earlier, the group of fungi known as white rot was the first type to break down lignin. That group is still a major player, leaving wood flaky and bleached-looking in the forest.
"White rot is amazing," said Hibbett.
To break down lignin, white rot fungi use strong enzymes, proteins that speed up chemical reactions. These enzymes split many of lignin's chemical bonds, turning it into simple sugars and releasing carbon dioxide into the air. White rot is still better at rending lignin than any other type of fungus.
Brown Rot
Compared to white rot's powerful effects, the scientific community long thought the group known as brown rot fungi was weak. That's because brown rot fungi can't fully break down lignin.
Recalling his college classes in the 1980s, Barry Goodell, a professor at the University of Massachusetts Amherst said, "Teachers at the time considered them these poor little things that were primitive."
Never underestimate a fungus. Even though brown rot fungi make up only 6 percent of the species that break down wood, they decompose 80 percent of the world's pine and other conifers. As scientists working with JGI in 2009 discovered, brown rot wasn't primitive compared to white rot. In fact, brown rot actually evolved from early white rot fungi. As the brown rot species evolved, they actually lost genes that code for lignin-destroying enzymes.
Like good cooks adjusting to a new kitchen, evolution led brown rot fungi to find a better way. Instead of unleashing the brute force of energy-intensive enzymes alone, they supplemented that enzyme action with the more efficient "chelator-mediated Fenton reaction" (CMF) process. This process breaks down wood cell walls by producing hydrogen peroxide and other chemicals. These chemicals react with iron naturally in the environment to break down the wood. Instead of fully breaking down the lignin, this process modifies it just enough for the fungus to reach the other chemicals in the cell wall.
There was just one problem with this discovery. In theory, the CMF chemical reaction is so strong it should break down both the fungus and the enzymes it relies on. "It would end up obliterating itself," said Jonathan Schilling, an associate professor at the University of Minnesota.
Scientists' main theory was that the fungus created a physical barrier between the reaction and the enzymes. To test that idea, Schilling and his team grew a brown rot fungus on very thin pieces of wood. As they watched the fungus work its way through the wood, they saw that the fungus was breaking up the process not in space, but in time. First, it expressed genes to produce the corrosive reaction. Two days later, it expressed genes to create enzymes. Considering fungi can take years or even decades to break down a log, 48 hours is a blip in time.
Scientists are still trying to figure out how much of a role the CMF process plays. Schilling and like-minded researchers think enzymes are still a major part of the process, while Goodell's research suggests that CMF reactions do most of the work. Goodell's team reported that CMF reactions could liquefy as much as 75 percent of a piece of pine wood.
Either way, the CMF process offers a great deal of potential for biorefineries. Using brown rot fungi's pretreatment could allow industry to use fewer expensive, energy-intensive enzymes.
A Close Collaboration
Not all fungi stand alone. Many types live in symbiosis with animals, as the fungus and animal rely on each other for essential services.
Partnerships with Rumens
Cows and other animals that eat grass depend on gut fungi and other microorganisms to help break down lignin, cellulose, and other materials in wood's cell walls. While fungi only make up 8 percent of the gut microbes, they break down 50 percent of the biomass.
To figure out which enzymes the gut fungi produce, Michelle O'Malley and her team at the University of California, Santa Barbara grew several species of gut fungi on lignocellulose . They then fed them simple sugars. As the fungi "ate" the simple sugars, they stopped the hard work of breaking down the cell walls, like opting for take-out rather than cooking at home.
Depending on the food source, fungi "turned off" certain genes and shifted which enzymes they were producing. Scientists found that these fungi produced hundreds more enzymes than fungi used in industry can. They also discovered that the enzymes worked together to be even more effective than industrial processes currently are.
"That was a huge diversity in enzymes that we had never seen," said O'Malley.
O'Malley's recent research shows that industry may be able to produce biofuels even more effectively by connecting groups of enzymes like those produced by gut fungi .
Termites as Fungus Farmers
Some fungi work outside the guts of animals, like those that partner with termites. Tropical termites are far more effective at breaking down wood than animals that eat grass or leaves, both of which are far easier to digest. Young termites first mix fungal spores with the wood in their own stomachs, then poop it out in a protected chamber. After 45 days of fungal decomposition, older termites eat this mix. By the end, the wood is almost completely digested.
"The cultivation of fungus for food [by termites] is one of the most remarkable forms of symbiosis on the planet," said Cameron Currie, a professor at the University of Wisconsin, Madison and researcher with the DOE's Great Lakes Bioenergy Research Center.
Scientists assumed that the majority of the decomposition occurred outside of the gut, discounting the work of the younger termites. But Hongjie Li, a biologist at the University of Wisconsin, Madison, wondered if younger insects deserved more credit. He found that young workers' guts break down much of the lignin. In addition, the fungi involved don't use any of the typical enzymes white or brown rot fungi produce. Because the fungi and gut microbiota associated with termites have evolved more recently, this discovery may open the door to new innovations.
From the Lab to the Manufacturing Floor
From the forest floor to termite mounds, fungal decomposition could provide new tools for biofuels production. One route is for industry to directly produce the fungal and associated microbiota's enzymes and other chemicals. When they analyzed termite-fungi systems, scientists found hundreds of unique enzymes.
"We're trying to dig into the genes to discover some super enzyme to move into the industry level," said Li.
A more promising route may be for companies to transfer the genes that code for these enzymes into organisms they can already cultivate, like yeast or E. coli. An even more radical but potentially fruitful route is for industry to mimic natural fungal communities.
For millions of years, fungi have toiled as short-order cooks to break down wood and other plants. With a new understanding of their abilities, scientists are helping us comprehend how essential they are to Earth's past and future.
Photo:
The evolution of white rot fungi most likely played a large role in trees beginning to decay about 300 million years ago. The fungus Schizophyllum commune is one modern example of a white rot fungus. Credit: Photo courtesy of Nathan Wilson
white rot fungi