Blueberry cultivars in the United States and North America, in general, can be affected by many common diseases. This can be a concern for new blueberry growers if they don’t know how to treat the problem.
In this article you’ll learn about the various blueberry bush diseases that can infect your bushes, along with how to treat them and prevent future occurrences.
Blueberry bush diseases can come in a variety of forms and each one requires specialized action to treat and prevent them. Some pose greater threats than others to your blueberry harvest, so educating yourself about each one is a necessary part of growing blueberry shrubs in your garden.
Bacterial Canker
A bacterial disease that enters the plant through cuts in the wood and affects the blueberry stems. The lesions on the trunk turn into reddish-brown or black cankers that are one inch in diameter. With time, the canker extends to the entire length of the stem, and it kills the plant.
Symptoms
The first symptoms may appear in January and early February due to a winter injury. Aside from brown and black cankers, the most common symptom is dying sprouts.
How to manage
- Prune out the diseased stems.
- Apply copper in fall and spring.
How to prevent
The infection enters the plant through a frost injury, insect damage to the wood or even cuts made by pruning tools.
- Sterilize your instruments
- Prune carefully to not wound the plant.
- Use protection against frost.
Crown Gall
Crown Gall is one of the canker diseases affecting blueberries. It affects the entire plant, starting from the trunk where bulges will grow near the roots. It’s a bacterial disease that is present in ventilated soils, such as sandy loams.
Symptoms
You’ll notice tumor-like spheres (galls) at the base of canes, on the roots, or the lower stems of the bush. The galls will be cream-colored at first and will turn dark brown or black late on. They attach themselves to the wound or pruning cuts the shrub may have and they will affect the plant growth.
How to treat
- Use a pruning knife to remove galls.
- Seal the wounds on the trunk.
- Remove the plant if it doesn’t get better.
Prevention
- Limit watering.
- Plant the bush only a couple of inches into the soil.
- Be careful not to injure the plant.
Armillaria root rot
This is a fungal disease caused by Armillaria Mellea that weakens the trunk and decays the wood. Even after the plant is cut down, the infection will survive a long time in debris and old stops and roots, so when a new bush is planted close by, it will transfer to it.
Symptoms
- Yellowish and small leaves.
- Dead stems on the upper part of the bush.
- Yellow mushrooms surrounding the base in the fall
- White sheets of fungal growth on the wood.
How to manage
- If plant hosts are from a line nearby, protect the plants with plastic sheets.
- Water frequently occurs during droughts.
- Place drip irrigation emitters should be placed away from the crown.
- Remove and destroy the plants that have been infected the most.
- Soil fumigation can help reduce the inoculum. Make sure to remove all roots larger than 1-inch in diameter and right after fumigation, apply plastic tarps.
How to prevent
If a plant is infected and unstable, remove the plant to avoid the spread of the disease. Make sure to remove roots and stumps of infected trees and clear the soil from any vegetation. Leave the soil bare for one to three years.
Alternaria Fruit Rot
This disease is caused by a fungus, Alternaria tenuissima. The plant can be infected any time between late bloom and fruit maturity. However, the infection will remain dormant until the fruits have matured. It can be spread from dead, infected twigs from the previous crop, into the newest sprouts.
Symptoms
Disease symptoms include:
- Deformed berries: These deformities appear as carvings on fruit skin, near the lower end of the berry.
- Gray mold on fruit.
- Infected berries are watery and break easily.
- Leaf scar on infected bushes.
How to manage
The most effective way to manage this disease is by chemical control. Use fungicide sprays on infected bushes after blooming, during the disease’ dormant season.
How to prevent
Prevention can be achieved through different control measures:
- Remove dead fruits and branches.
- Space your blueberry planting apart to allow ventilation.
- Avoid overhead irrigation.
Botrytis blight
Botrytis blight is a disease of blueberry caused by Botrytis Cinerea. It affects blueberry plants and other ornamental plants, by infecting their wounds and senescent plant tissue. During the bloom, the flower corollas (the fused petal of the flower) senesce and are at high risk for infection, especially if they don’t drop right after pollination. Once it has entered the senescent tissue, the fungus will spread into the ovary and then into the berry stems.
The development of this disease depends on environmental conditions and will spread easily in high humid climates, combined with frequent irrigation.
Symptoms
Abnormal growth of flowers: Instead of healthy flowers, they may show flecks and brown spots and will rot quickly. You may also see soft brown spots on leaves and stems after a cool damp period.
How to manage
Fungicide applications from preboom through the end of bloom may help.
How to prevent
- Do not over water your bushes.
- Don’t frequently use overhead irrigation.
- Leave enough space between bushes to allow air circulation.
- Remove infected twigs every year.
- Keep the area free from weeds.
- Avoid the use of fertilizers late in the season.
- Pick fruits as soon as they mature and store them in a cold place.
Mummy berry
Mummy berry is a fungal infection that affects berry growth and can severely damage fruit production. What this means is the plant won’t bear actual fruit, but small fungal masses that look like mummified berries.
Symptoms
Characteristic symptoms will appear mostly in the lower stems, closer to the soil. Diseased bushes will have young dead leaves, as well as wilting shoots and flower buds.
How to treat
Treatment for this berry disease consists in:
- Apply a layer of mulch in late winter or early fall.
- Keep a close eye on your bushes for any apothecia (fungal fruiting cups) and apply fungicide if there are any.
How to prevent
Berry infections can seriously damage the yearly fruit yield. Thoroughly clean the area underneath and around the blueberry bushes, and remove all residues from the previous season. Apply mulch at the base to bury any remaining mummified fruit hidden in the soil.
Silver Leaf
Like many other blueberry bush diseases, silver leaf affects the bush through cuts and wounds in stems and limbs. The sources of inoculum are spores on previously infected bodies which are blown around by the wind and end up attaching themselves to new plants.
Symptoms
Young blueberry leaves turn silver. It can start on a couple of branches, but it gradually spreads to the whole bush.
Roots may seem intact, but infected stems may show a brown heart with purple to brown concentric rings. Furthermore, the plant will show some discoloration at the base of infected branches and the base of the trunk.
Treatment
Unfortunately, there is no method of control once the plant has already been contaminated. Remove all diseased wood to prevent further spread of the disease.
How to prevent
- Destroy the plants that show symptoms and make sure to clean out any plant debris.
- Pay close attention when taking care of the bushes to not damage them.
- Apply chemical agents to protect any wound or pruning cuts the shrub may have.
Powdery Mildew
Powdery mildew is a leaf disease and one of the most common and easily identifiable diseases in blueberry plants. It favors high humidity zones with moderate temperatures, in conditions where there is low light and poor air circulation.
Symptoms
- Faint white powder on the upper surface of older leaves.
- Some necrotic areas will start to appear on the leaf.
- Tiny black fungal bodies on infected leaves.
- White spots may also appear on stems, flowers, and even fruits.
How to cure
Most products available on the market can only control the infection, so it’s not always possible to eliminate the problem. There are, however, some homemade remedies that can help treat Mildew:
Baking soda solution: In one gallon of water, mix 1 tablespoon of baking soda with half a teaspoon of liquid soap.
Potassium bicarbonate: In one gallon of water, mix 1 tablespoon of bicarbonate and half a teaspoon of liquid soap and spray on the affected plants.
Milk: A mixture of milk and water will be enough against the disease.
Neem Oil: Even by itself, the oil has a great effect against Mildew.
How to prevent
- Don’t overcrowd the plants and place them in a well-ventilated area.
- Find a spot where the plants will get at least six hours of light per day.
- Don’t over fertilize.
- Use a slow-release product that will help control growth.
- Use drip irrigation.
Fusicoccum Canker
Also referred to as Godronia Canker, it’s considered to be one of the most serious canker diseases and it develops during cool and wet weather. Susceptible cultivars are infected through wounds or pruning cuts or other openings in the bark.
Symptoms
Small lesions on new stems or buds, which grow bigger each year until they encircle the stems entirely and cause their deaths. These cankers usually start from reddish-brown and as they grow their center turns grey, while the margins turn a darker brown.
The disease can also attack the leaves on infected branches and you will notice that they turn brown sooner in the fall.
How to manage
Currently, no fungicide will help eliminate the disease. To prevent its spread, you can:
- Prune out and destroy infected branches and never use plants with injured branches.
- Don’t use overhead irrigation.
- Grow resistant cultivars such as Rubel and Rancocas.
Witches Broom
The root of this disease is a rust fungus which causes a cluster of small branches (witch’s broom) to form at the base of the bush. The fungus grows in the bark and spreads to the whole plant.
Symptoms
Symptoms are easily identifiable. The first one is the mass of branches at the base of the plant. The infection causes leaves to remain small and not develop. Shoots will have a reddish and spongy bark, instead of the usual green.
How to cure
It’s not possible to cure infected plants and fungicides cannot prevent new infections, so it’s recommended to remove and dispose of the diseased plants.
Pruning witches’ brooms will reduce the symptoms temporarily.
How to prevent
Since the disease affects figs as well, don’t place the two plants within 500 yards of each other. Remove and burn the diseased plants and clean out dead twigs and other debris before planting a new bush. This way, the disease won’t spread to healthy bushes.
FAQs
What diseases do blueberry bushes get?
Aside from the ones we have just discussed, blueberries can also suffer from:
- Anthracnose (ripe rot)
- Bacterial Leaf Scorch
- Leaf spot diseases
- Leaf Rust
- Stem canker and Stem Blight
- Twig Canker and Twig Blight
- Phytophthora Root Rot (Phytophthora Cinnamomi, Phytophthora Ramorum)
What is killing my blueberries?
Overwatering is generally the number one cause of death. The most noticeable symptom of overwatering is leaf drops.
What are Highbush blueberry diseases?
The diseases affecting Highbush blueberries are the same as the ones affecting other blueberry varieties and include:
- Mummy Berry
- Anthracnose
- Phytophthora Root Rot (Phytophthora Cinnamomi, Phytophthora Ramorum)
- Blights and Cankers, such as Botrytis Blight and Twig Blight.
Here is all the information you will need to treat these 10 common blueberry bushes diseases. Remember that certain cultivars are at greater risk and not even the right fungicide program will be able to do much.
Related Blueberry Growing Resources:
- 9 Common Blueberry Pests: How To Identify and Get Rid of Them
- How to Prune Blueberries
- How to Grow Blueberries: A Complete Guide
- When Is the Right Time To Pick Blueberries?
Blueberry Recipes:
- Mindblowing Deliciously Healthy Blueberry Muffins
- The Most Amazing Blueberry Coffee Cake You’ll Ever Make!
- Fresh and Easy Veggie and Blueberry Smoothie
- The Most Delicious Homemade Blueberry Pancakes, Ever!
Excited for more blueberry content? Then check out our blueberry page to learn all about how to grow, care for, and harvest this delicious fruit!