Monday , July 6 2020

How to prevent and control Armillaria root rot in apricots

Armillaria mellea

The mushroom Armillaria can attack all fruit trees, including apricots.

Although fumigation is sometimes recommended, this usually does not work. This fungus is unusually resistant to fungicides.

In addition, the organism often lurks in pieces of old infected trees or in roots in the ground where fungicides cannot come into contact with it.

There is no good cure for it Armillaria Root rot, but keeping your plants healthy and stress-free can help prevent infections.

Armillaria attacks around the world

While Armillaria mellea is the most common source this kind of root rotmany other species could be involved.

For this reason, the disease is usually only referred to as Armillariaor the honey mushroom or mushroom.

These fungi can remain in the soil so well that some colonies are thousands of years old. And a colony of Armillaria in Oregon is considered the largest organism in the world.

Honey fungi infect thousands of plant species around the world and are very common pathogens in hardwoods or conifers.

Since home gardens and orchards are often located on land where hardwood forests used to live, there is a very good chance that Armillaria hides in your floor.

Symptoms of apricot trees

This disease can settle without you realizing it. You may notice the infection first if your apricot becomes infected after the age of 5.

If so, your apricot tree has small leaves and poor final growth until the unthinkable happens – it suddenly collapses in summer.

Armillaria root rot infects the base of a tree, causing loss of bark and destruction of the roots.
Armillaria root rot produces a white mat and causes loss of bark, which hinders the flow of nutrients from the roots. The roots will rot at some point. Photo courtesy of Rebekah D. Wallace, University of Georgia,, under CC 3.0.

A classic symptom in orchards is that the original plant infected with this type of root rot is surrounded by a circle of infected trees.

Fan-shaped white Armillaria mycelium mats growing on the surface of a tree.
White fan-shaped mycelium mats are an indicator of the presence of Armillaria. Photo courtesy of Steven Katovich, USDA Forest Service,, under CC 3.0.

You can see if the cause is Armillaria by looking between the bark and the wood of the crown. If this fungus is the culprit, you will likely find a fan-shaped white mushroom mat that grows between the bark and the wood.

Armillaria rhizomorphs on the inside of a tree with bark removed.
Armillaria spreads through rhizomorphs that are located between the bark and the inner surface of the tree.

The mushrooms produce characteristic structures called Rhizomorphs, Dark strands of fungal threads that can remain in the soil indefinitely. You can strike as soon as you feel a weakened weakening.

Another telltale sign is the brown mushrooms, which are produced at the base of trees in summer or autumn. The fact that these mushrooms are edible is probably a little comfort.

How the mushroom spreads

A small piece of an infected root or the remains of a tree stump from an infected tree are all this fungus needs to gain a foothold.

However, this is the most common Armillaria Spread is when the root of an infected tree grows to the root of your apricot. The fungus can then spread to your plant.

This fungus also spreads through the rhizomorphs mentioned above. You can think of these strands as foraging for plant roots. In this case, they look for uninfected roots and infect them.

A less common type of infection is wind-blown spores from the fungi. However, these spores can only grow on damaged or already dead wood.

How to prevent Armillaria disease on apricots

Before planting your apricot tree, there are a few steps you can take to minimize the risk of infection:

1. Prepare the planting area

Comb through the soil and remove old roots or pieces of wood that could house the fungus.

Agriculture Victoria, the agricultural portfolio of the Department of Employment, Districts and Regions of the Australian Government of the State of Victoria, recommends taking steps with native trees before removing them to plant your apricot.

First belt or bark wild trees in the area by removing a narrow strip of bark from the entire circumference of the trunk, and leave the tree alone for at least six months. With depleted starch reserves, belted samples become less of an infection target.

A number of experts recommend that you plant an annual crop for several years to reduce the amount of Armillaria present in the soil before stone fruit is planted.

And always make sure that the soil drains properly before planting! Excessive moisture can harbor fungal growth.

2. Do not grow lawn grass near your tree

Growing grass to the base of your tree can encourage the honey fungus to attack your apricot.

3. Keep your tree in good health

After establishing your tree, try to maintain the conditions under which it stays at the peak of health. Armillaria will sense when trees are weak and can infect them.

Proper fertilization helps as well as treating diseases or insect infestation that would cause your apricot tree to lose its leaves.

Drought increases the risk of infection. Cultivation of cover crops increases soil moisture and helps prevent drought stress.

Floods also increase stress on your plants.

Factors that you have no control over and increase the risk of infection include nearby structures or fillings.

How to treat a slightly infected tree

Air can be deadly ArmillariaSo if you get the infection early, drastic measures can be helpful.

Dig a trench by removing the soil from the base of the tree trunk and its main roots. Do this in a radius of about 2.3 feet.

High pressure water can help you achieve this.

Remove the diseased roots and bark and burn them. Then use a plastic paint to paint the cuts.

Keep the ground away from your tree and you might be hoping to save it.

The University of California’s Integrated Pest Management (IPM) program recommends that you place a tarp around the sides of the trench to prevent any remaining fungus from reaching the ground through to your other trees.

If your tree is severely infected, you need to remove it and burn the stump and any roots you can find.

Armillaria is a common pathogen

Armillaria attacks native trees and shrubs around the world.

This mushroom serves a purpose in nature by helping to keep forests away from dying trees. However, this tendency can be fatal to your apricot tree.

If you plan to plant an apricot tree, clean the bottom of pieces of wood and roots left from trees that have previously grown in the country.

Since the honey fungus only attacks weakened apricots, minimizing the strain on your tree can help protect it from this possible attack.

Ripe Armillaria mushrooms growing at the base of a tree.

If you spot the infection early enough, you may be able to save your plantings.

However, if your tree is too far away, you have to be ruthless and destroy it.

This fungus does not infect grasses, and if you grow them on the construction site several years before transplanting, it can help clean the soil.

After all, you don’t want to start a colony that can live thousands of years!

Did you have one Armillaria Root rot infection on an apricot tree? If so, let us know how your tree has fared and what steps you have taken to prevent or control it.

About Christian

Christian Joshua Ferguson is a local activist who enjoys walking, social media and jigsaw puzzles. He is entertaining and smart, but can also be very greedy and a bit lazy. he also likes to write about plants

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