How to Identify and Manage Armillaria Root Rot in Pear Trees

Armillaria mellea

There is a plant disease called honey fungus or honey fungus, and I find it cute. What could be bad about honey fungus?

Much.

Sometimes called oak root fungus – although it infects many more species of trees than just oaks – Armillaria root rot and stump rot, as botanists call it, is a horror.

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It is an absolute threat to apple, apricotswalnuts and other important crops. In the southeast, it destroys fruit trees as Godzilla crashes into the city.

Pears are not as susceptible to disease as some other fruit trees, but they do not have any immunity. When Armillaria comes calling, your pears are in serious trouble.

You really don’t want to have to deal with this disease. So in this guide we’ll cover its origins, how to avoid it, and what to do if it infects your pears.

Here’s what we’ll discuss:

What is Armillaria?

Armillaria rot is caused by a fungus Armillaria mellea. Fungi thrive in cool, moist weather.

Unlike some other fungal diseases, which are often invisible, this disease manifests itself as actual fungi – fruiting bodies – on infected trees, as well as large patches of spores hidden under the bark.

For decades, pear growers assumed their crops were immune to the disease, as pears had previously developed some resistance to the fungus.

But in the 1990s, the disease began to spread rapidly in California pear orchards. Today, no one is immune.

Armillaria mellea found worldwide in temperate regions.

This fungus requires a host to survive, meaning it cannot live in soil alone, even small pieces of old roots or broken wood can act as hosts. The fungus can live on this type of material for decades.

If you grow pears in an area that was once inhabited by other susceptible tree species, there is a good chance the pathogen is clinging to dead roots underground.

The same thing happens if you build or plant trees in an area where the forest has been cut down in the last ten years or so.

Know

Armillaria canker can be a difficult disease to treat. On some pear trees, the only visible symptom is that they look sad, lifeless and not growing well.

The pear may not produce as many fruits as before and it may not look as attractive, with leaves falling off or turning yellow.

Other times, the plant will wilt suddenly and die completely within a few weeks.

This is the same fungus and the same disease, but the two reactions are extremely different.

Even more annoying is that these symptoms can be caused by a variety of problems. Too much or too little water can cause the plant to droop and turn yellow. Feed gophers or Phytophthora Rot can exhibit some similar symptoms.

The best way to be sure you have Armillaria is to take a shovel and dig up some soil at the base of the pear tree. Scrape off some of the bark at the base of the trunk and some of the larger roots.

If so, you will see a creamy or white cottony or felt-like layer, which is the mycelium or root-like mass of the Armillaria fungus.

Peel back some of the bark and you can see the mycelium fans, which are white fan-like shapes formed by the growth of mycelium.

If you poke the wood with your finger or a shovel, it will be spongy and soft, and you can even smell the fresh mushroom scent.

In addition to or instead of hyphae, you may also see hyphal cords or rhizomes. These black, thread-like structures also serve as the roots of the fungus.

Finally, in the fall or during the rainy season in summer, fall or early winter, you can often see tan or honey-colored fruiting bodies – mushrooms – at the base of pear trees.

They are sometimes called honey mushrooms and they grow on both dead and living wood.

Although you may risk losing your plants to this fungus, the good news is that these mushrooms are edible.

Can you swap your pear tart for a mushroom tart? Just be 1,000 percent sure you’ve identified them correctly and always cook them thoroughly before eating.

Biology and life cycle

Armillaria reproduces in the living wood and roots of infected trees.

It appears as mushrooms at the base of trees in late summer or fall, each mushroom has a cap and notched leaves.

As they age, the caps collapse and release spores, which fall onto the host wood and begin to reproduce.

The fungus then overwinters in the wood as mycelium or rhizome.

Once attached to a tree, the fibrous roots can extend up to 10 feet underground to reach another host.

The fungus finds a new host to infect through the injured area and then moves down the roots and into the canopy. Eventually, the fungus will surround the tree, destroying the cambium layer and killing the tree.

The fungus can also spread in water and on infected wood.

Control method

I don’t want to be the bearer of bad news, but here we are: There is no effective way to control this disease.

Although experts have yet to find an effective way to deal with this disease, there is one final solution you can try if your pear tree is infected.

One way to slow or stop the progression of the disease is to carefully dig a foot down around the diameter of the tree to expose the lower stem and upper roots.

Prevent all plant debris and soil from falling into the hole you dug and avoid letting water run into the trench.

If you keep the area clean and dry throughout spring, summer, and fall, the disease will stop.

You can bury the roots again in late fall.

This disease attacks all types of trees, but oak, black walnutAnd Willow most vulnerable.

If you are serious about growing pears, avoid planting them near any of these trees.

Prevent

Let’s talk about prevention. When you Water your pear treeWater flows from the tree trunk down the ground to the drip line.

You should also be very careful not to injure the plant. Young specimens are especially sensitive, but older plants can die quickly if you damage them. while pruningmowing, or edging.

You should also remove any mushrooms you find near the tree as they can open up and release spores into the wind.

If you are planting in an area where sensitive trees have previously been planted or where forests have been cleared, it is ideal to dig down and remove any remaining roots.

Then wait a few years for the living plant tissue to die.

Some pear varieties are more resistant to armillaria than others. Pyrus betulaefolia, P. calleryanamost French pear varieties, hybrid varieties on ‘Bartlett’ Rootstocks and hybrids on ‘Old Home’ x ‘Farmingdale’ rootstock are the most resistant to disease.

If you want to be cautious, grow these plants.

Finally, try to keep your plant as healthy as possible by fertilizing, watering, and pruning properly. You can Learn more about growing pear trees in our comprehensive guide.