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What Causes Brown Spots on Blueberry Leaves? Revealed

What Causes Brown Spots on Blueberry Leaves? Revealed

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Other than providing fresh and delicious Blueberries to munch on while strolling in your garden, Blueberry bushes are a brilliant shiny green plant, adding joy to your garden.

We all love Blueberries, not just for their flavor but also for all those healthy nutrients and antioxidants they give to our bodies. On top of that, Blueberries are fairly easy to cultivate with just a little bit of preparation.

But if you lack in preparation for planting a Blueberry bush, you might soon see your plant telling you that it’s not happy. One of the most common ways for the plant to tell you this is brown spots on its foliage.


What Causes Brown Spots on Blueberry Leaves?

Brown spots appearing on Blueberry leaves means that your plant has developed one of the many Blueberry leaf spot diseases. More often than not, these brown spots are a result of a fungal disease. Anthracnose and septoria are the two most common fungal diseases in Blueberries. However, brown spots can also be a result of a bacterial condition such as Bacterial Blight.


Identifying the Leaf Spot Disease on Your Blueberry Plant

Firstly, you need to know that the vast majority of fungal and bacterial diseases in plants develop in high-humidity conditions. You might notice leaf spot in Blueberry plants kept in greenhouses or planted in dense vegetation.

If spotted and identified early, the disease can be eliminated without much inconvenience. But once a fungal or bacterial condition takes hold in the Blueberry plant, it will only spread to other plants and cause significant leaf shedding.

The treatment for a leaf spot condition depends on the successful diagnosis of a plant’s disease. Of course, we cannot go about spraying fungicide when the problem is bacterial.

To the common eye, brown spots on leaves are plain brown spots. Everyone can not differentiate two different diseases that cause similar-looking brown spots on a plant.

However, you being a plant parent, have to develop a critical eye to identify your plant’s ailment.

Here’s a list of what brown spots on your Blueberry leaves may look like when caused by a particular pathogen.


  • Anthracnose – It is a fungal disease that emerges after a Blueberry plant has bloomed and stays until after the fruit has ripened. The initial signs include minute red flecks spread over the leaves and stems. Flecks gradually increase in size to form brown lacerations and will spread to other parts of the plant.


  • Septoria – This is also a fungal disease that is most noticeable between the months of July and September. The spots caused by this condition have a purplish hue to them. They might also be white in the middle and purple on the edges.


  • Double Spot – When this infection takes root, the initial spots are very tiny. But as summertime comes to an end, the spots become noticeably larger when the fungus develops around the initial site to form a fan-shaped larger spot. This is also a fungal disease.


  • Gloeocercospora­– Spots developed by this fungal condition appear in mid-summer. They are dark brown circles of medium to large size.


  • Alternaria – Alternaria leaf spot typically emerges in spring, when temperatures start rising after damp and chilly conditions. The gray or brown spots can be round or irregular in shape, with a red border. Alternaria directly affects the fruit, and the produce on an affected Blueberry bush appears shriveled.


  • Valdensinia – This condition causes large circular spots that resemble a bull’s eye. They can quickly spread to the stems and other parts of the plant and cause major leaf drop.


  • Blueberry Leaf Rust – Rust usually appears late in the growing season but can also show signs of infection in the spring following a mild winter. Initially, yellow lesions appear, which gradually turn to a reddish-brown. The underside of the leaves has yellow or orange bulging spots.


  • Bacterial Blight – This bacterial disease can only affect old foliage (growth from previous growing seasons). It appears in late winter when Blueberry stems develop watery abscesses. These spots slowly become red-brown, and if left unattended, they take the form of black canker.


  • Botrytis Blight – This condition is also known as gray mold and emerges as brown spots on fresh growth. The new growth is significantly affected, and the fruits appear shrunken while a gray mold takes over the foliage and fruits.


Treatment Options for Blueberry Leaf Spot

Diagnosing leaf spot diseases was the long and boring part. Every gardener wants to know what to do to take action against the nasty fungus or bacteria that’s bothering their beautiful Blueberry bush.

The first thing on your agenda should be providing an environment to your plant that protects them from attacks in the first place. This will ensure that whatever treatment you apply works effectively and that your Blueberry doesn’t get attacked in the future.

This includes providing your plant with good air circulation and cleaning out all plant debris before wintertime every year. Most fungi overwinter in the plant debris, so cleaning your berry patch can prevent you from having problems for sure.

Your berries should enjoy an open space with direct sunlight and well-draining acidic soil.

Fungal infections can spread relatively easily. Even you can act as a pathogen carrier around your berry patch or garden, so you must be very careful. Effectively dispose of infected foliage and clean your garden shears. Do not touch other plants after touching an infected plant.

If the plant has a fungal problem, get the correct fungicide and apply it only on the areas with leaf spot symptoms. Apply it as soon as you diagnose the condition and follow up every two weeks until winter.

Bacterial Blight can also be effectively handled with fungicides that contain copper and Mancozeb.


Frequently Asked Questions about Brown Spots on Blueberry Leaves


Are brown spots on Blueberry leaves a result of over-watering?

Overwatering and root rot can develop red-brown areas on Blueberry leaves. But these brown areas are not exactly spots as they are just a result of leaf tissue drying off due to lack of water.


How fast can a fungal disease spread in Blueberry plants?

Both fungal and bacterial diseases spread the fastest in warm, damp, and low-light conditions. These are ideal conditions for fungi to thrive, and a fungal disease may spread from the leaves to the rest of the plant in a matter of days. However, the spread can be significantly slowed down by providing better conditions to plants.