The 6 Most Common Plant Diseases in New England

The 6 Most Common Plant Diseases in New England

Like humans, plants can come down with various diseases. In certain regions, some plant diseases are more likely to occur. In our New England region, there are several common diseases seen in plants. These varying infections may occur throughout different times of the year, or on different plant species.

To learn more about the six most common plant diseases seen in New England, keep reading below. We’ll explore common diseases that affect plants in New England and how to identify them.

Tree Disease - Apple Scab

COMMON TREE DISEASE 1: APPLE SCAB

As the name suggests, Apple Scab affects apples and their leaves. New England is home to many crab apple trees, which are often affected by apple scabs. 

What causes apple scabs?

Apple scab is caused by a specific type of fungus, known as Venturia Inaequalis. This fungus infects the leaves of the fruit of apples, causing significant damage if left untreated. Scabby fruit not only looks unattractive but makes the fruit unable to be eaten

When do apple scabs start?

Apple scabs are commonly seen on apple trees in the early spring, as fungal spores from leaves infected from last season. 

Identifying an Apple Scab

Apple scabs are visible to the human eye. You may notice spots that cover the leaf, that is circular with fringed borders. Over time, these spots may turn black or dark brown. The spots may be raised and fuzzy. As the fruit grows, you may notice that the apple becomes deformed or cracked in appearance.

How are Apple Scabs managed?

Starting at bud break, apple scabs can be managed with three foliar fungicide treatments. These fungicide treatments do not cure the leaf spots but can protect healthy leaves from becoming damaged too.

Tree Disease - Cedar Apple Rust

COMMON TREE DISEASE 2. Cedar Apple Rust

Like Apple Scab, Cedar Apple Rust is another disease that can affect crab apple trees and cedars. Cedar apple rust is one of the most common plant diseases in eastern North America. It is caused by a group of fungi that requires two or more hosts to complete the life cycle.

What causes cedar-apple rust?

Cedar Apple Rust is caused by a fungal pathogen known as Gymnosporangium Juniperi-Virginianae, which requires two hosts.

When does cedar apple rust start?

Cedar Apple Rust, amongst the most common plant diseases in New England, usually occurs in late spring to early summer. This is the period between April through May.

Identifying Cedar Apple Rust

With cedar apple rust, there will be noticeable spores that are visible on the tree. Depending on the type of tree, spores may differ in appearance slightly. These produce gelatinous horns or spots. On crab trees, leaf spots will first turn yellow and then switch to bright red or orange. On cedar or juniper trees, the Cedar Apple Rust will present as woody galls on branches or twigs.

How is Cedar Apple Rust managed?

Fungicides are used to help prevent the spread of Cedar Apple Rust.

Tree Disease - Needle Cast

COMMON TREE DISEASE 3. Needle Cast

Needle Cast affects several types of trees including pines, firs, and spruces. Many species of spruce trees are highly susceptible to this fungal infection.

What causes Needle Cast?

Needle Cast is caused by a fungus known as Rhizosphaera Kalkhoffi. In some cases, other types of fungus can cause needle casts too. The infected needles with this fungus will produce spores that ultimately can spread to other healthy needles on the tree.

When does needle cast start?

Infected needles with Needle Cast often show in the mid to late summer. They may begin as bright yellow, ultimately changing color to a brown color. The needles begin to drop after 12 to 15 months of infection.

Identifying Needle Cast

Needle cast on trees can often look like the browning of the needles or even loss of needles. The innermost needles on the lower branches of the tree are often affected.

How is Needle Cast managed?

Needle cast is managed using fungicides that contain copper. These fungal treatments cannot cure an existing needle cast disease on a tree, but they can help stop the spreading of healthy needles. This type of treatment is done every three to four weeks and through periods of wet weather.

Tree Disease - Leaf Spot on Mountain Laurel

4. Leaf Spot of Mountain Laurel

Leaf Spot of Mountain Laurel is one of the most common plant diseases in New England. Almost every Mountain Laurel is likely to have this disease.

What causes Leaf Spot of Mountain Laurel?

Leaf Spot of Mountain Laurel is caused by a fungus known as Mycosphaerella colorata (Phyllosticta kalmicola).

When does Leaf Spot of Mountain Laurel start?

Leaf Spot of Mountain Laurel can happen at any point throughout the year.

Identifying Leaf Spot of Mountain Laurel

This disease causes visible light gray spots in a circle shape. They made have a brown or purple border. Fruiting bodies usually form in the center of these spots, and the leaves may cause prematurely due to this disease.

How is Leaf Spot of Mountain Laurel managed?

With three fungicide treatments, Leaf Spot of Mountain Laurel is easy to control.

TREE DISEASE - Dogwood Anthractnose

COMMON TREE DISEASE 5. Dogwood Anthracnose

This disease affects all native flowering dogwoods. It attacks twigs, branches, leaves, and trunks of dogwoods in cold, wet weather.

What causes Dogwood Anthracnose?

Dogwood Anthracnose is caused by a pathogen known as Discula destructive.

When does Dogwood Anthracnose start?

This disease is most likely to occur during periods of cool, wet weather in the spring or fall. However, it can occur at any point.

Identifying Dogwood Anthracnose

The leaf spots tend to be round and blotchy and may have tan centers or purple borders. The symptoms of this disease can vary quite a bit, but will often show flowering sprouts that are attached to the branches.

How is Dogwood Anthracnose managed?

Dogwood Anthracnose can be managed using four different fungicides. This disease affects the health and aesthetics of the tree significantly. Early detection is the best way to manage this common tree disease.

Tree Disease - Bleeding Canker of Beech

COMMON TREE DISEASE 6. Bleeding Canker of Beech

This disease commonly affects the bark of trees. Most often, this disease occurs on European beech trees, which are common within the New England region.

What causes Bleeding Canker of Beech?

This disease is caused by various pathogens which are all related species of Phytophthora.

When does Bleeding Canker of Beech start?

This disease is not specific to a season or time of year.

Identifying Bleeding Canker of Beech

Bleeding Canker of Beech appears as dark spots with wet or sappy material that oozes out of the cankers. Usually, the lowest parts of the tree trunk are affected by this disease first. Then, they may appear higher up.

How is Bleeding Canker of Beech managed?

This disease can be controlled with Phosphorous sprayed on the bark during the spring and fall seasons. Large beech trees should be treated proactively to prevent the disease. Early detection of Bleeding Canker of Beech is important in its success with treatment.

These six most common plant diseases in New England are certainly something to look out for. With preventive treatment, many of these common diseases are treatable and manageable.

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