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Past Articles Library | Trees | Plant Diseases and Pests of Pear Trees

Growing up, my mom and dad’s neighbor had a pear tree.  I have to be honest; I have eaten my share of these fresh fruits.  As delicious as these pears are, pear trees by nature do have a few problems.  Below is a general description of these plant diseases and pests along with solutions when available.  Keep in mind though; the best form of control is a clean garden and knowing your plant material.  Both of these approaches will help you get a jump on a problem before it can take over.  

Armillaria Root Rot

The Armillaria Root Rot or Oak Root Fungus is started by Armillaria mellea.  This fungus survives on dead roots in the soil.  When spores are released, they find homes in many pear trees.  The first signs of this disease start off with discolored leaves falling to the ground.  As the fungus progresses, the branches and then the trunk will die.  This will kill the tree.

Another sign that the disease is in the area is the appearance of golden brown colored mushrooms growing along the base of the plant. 

If you find this disease in your pear orchard, remove the plant material as soon as possible.  To prevent it from reoccurring, only plant root stock that is resistant to Armillaria Root Rot.


Scab fungus problem caused by Venturia pirina.  This fungus causes leaves to distort and turn yellow.  Once the leaves turn yellow, they fall off the tree.  Also, some leaves and fruit may develop dark green spots, which will correspond to a velvety growth on the underside of these leaves.

Since the fungus survives in fallen plant material, it is very important to keep the garden clean.  But do not just jump and start raking and composting.  If there is any question as to whether the disease is in the area, do not compost. 

As far as a chemical application goes, if you have a period of time in the spring when the weather is really wet, you may consider applying a copper soap.  This will be especially true when the leaf tips are first emerging.   

Pear Decline

This pear tree disease is caused by a phytoplasma that is carried by pear psylla.  This disease causes leaves to roll and turn red in the upper part of the tree canopy.  It also causes the tree to produce poor shoot growth, reduced leaf and fruit size along with premature leaf drop.

If you find that your pear tree has this issue, there really is nothing you can do for the existing trees.  In the future, you can choose root stock that is immune to the pear psylla.   

Crown Root Rot

Crown Root Rot is caused by Phytophthora spp, which can be found in soils that are poor drainers. 

The symptoms of this disease start off with the leaves.  The leaves will wilt but will remain on the tree.  The bark will have a dark brown appearance that becomes slimy with it is wet.  Cankers will form at the soil level on the trunk and the pear tree itself will have a stunted growth. 

To prevent this disease, starts off with proper watering.  Do not overwater the trees.  Nor should you plant the trees in soil that does not drain well.

There is no cure for Crown Root Rot.

Fire Blight

The bacterium that causes Fire Blight is Erwinia amylovora.  As the name indicates, Fire Blight causes the pear tree to have a burnt appearance.  The areas that look burned may even leak out water.  Leaves and stems will turn black and shrink up. 

To keep control of this disease, remove plant material that is diseased and dispose of.  If the spread of the bacterium is too bad, you may need to remove the plant material. 


Blast is caused by a bacterium called Pseudomonas syringae.  This bacterium thrives in cold and wet weather.  In doing so, you will need to apply a copper fungicide in the Fall and Winter to control it.  But before you run to the garden store, let’s take a look at what blast looks like. 

Blast will appear as waterlogged lesions on the leaf stem and will move up the middle of the leaf.  Leaves with blast will eventually turn black and die.  Cankers appear on twigs and branches.  These cankers may be so large that they girdle the twigs and/or branches.  When this happens, the girdled material will die.  Fruit may also have black sores.  

Spring Pear Cankerworm

The Spring Pear Cankerworm is caused by two insects, which includes the Paleacrita vernata and Alsophila pometaria.  These insects eat everything on the leaf but the veins.  Young fruit can also be found with depressions. 

There is no treatment at this time.   

Pear Psylla

Psylla pryicola is the insect that causes pear decline.  The insect itself is dark red to brown in color and resembles a small cicada.  This little insect will cause the pear tree to decline and finally will kill it.  The only non-chemical treatment is the application of insecticidal soap in the winter. 


Leafrollers come from two different insects, which include Argralotaenia veutinana and Platynota staltana.  These insects take the leaves and roll them.  The roll is kept together with silken thread.  As the larvae get hungry, it feeds on the rolled leaves.  In some situations, the silken thread or webbing can be found around the fruit.

To prevent and/or control the leafroller is not as difficult as it may seem since this is a moth.  The first step is to remove weeds from the base of the tree.  This simple plant material can act as a host for the leafrollers.  Second, know your plant material.  What this means is to become familiar with your plant material and act accordingly when there is a change.  If you do see the leaf rolling occurring, apply Bacillus thuringiensis.     


Codling Moth

As the name applies, the codling moth or Cydia pomonella is an insect that loves pears.  Signs of damage from this insect appear in the fruit itself.  Small holes will appear and may be blocked with a crumbly brown substance that is actually the waste of the insect.  While the hole on the surface my look shallow, it can go all the way to the core.

Both the adult and larvae are easy to identify.  The adults are dark brown with the larvae having a brown body with a pink head. 

Since the codling moth can have two to three generations in one season, it is paramount to get these little creatures under control.  The first stage of control comes from removing any unwanted trees from the area along with weeds.  This will keep the insects at bay by reducing the number of hiding place and host plants available.  Second, open up the plant material by properly pruning the pear tree so that the center is open and not congested with branches.  Lastly, remove and destroy any diseased fruit.

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