Like all food crops, blueberries are susceptible to various fungal diseases. Your best weapons against these are best planting practices, which help prevent disease in the first place.

This is especially important, as there are no fungicides approved for home use for many diseases.

These best practices are aimed at producing strong, healthy plants that can withstand disease, and at avoiding situations that contribute to the development of disease. They involve keeping plants clean, dry, and undamaged.

Companion Planting: Each crop has a garden buddy that helps out in some way: repelling pests, attracting pollinators, contributing nutrients to the soil. The best companion plants for blueberry bushes also thrive in acidic soil:

• Basil provides good groundcover, repels some pests
• Borage provides shade to blueberry roots during the hot summer months, attracts pollinators, and repels pests.
• Dill helps repel pests and adds fresh flavor to cooking and canning.
• Parsley repels pests and shades the blueberry bush roots.

You can also review our Food Gardening Network Companion Planting Chart for a full list of good planting partners for your garden.

Mulch: Mulch can help with water retention—but be vigilant and check for insect or fungal activity.

Watering: Water your blueberry bushes deeply about once a week (check the soil for dryness). Do not over-water. Soggy soil invites disease.

Other best practices include:

• Buy healthy, disease-free plants from reputable sources
• Plant your blueberry bushes in full sun
• Plant in sites with good drainage; if planting in open ground, choose a higher spot for better drainage
• Check plants regularly for signs of disease.

Common blueberry plant diseases

Here are some of the usual culprits that might infest your blueberry bushes. Remember, it’s important to remove infected plant material (leaves, roots) to prevent the spread of disease once it’s found its way onto your plant.

Alternaria Fruit Rot

Cause: Fungus

Symptoms:

• deformed berries (carvings on the fruit skin)
• gray mold on fruit
• watery berries that break easily
• scarring on leaves of infected bushes

How it Spreads:

• spores spread by rain, splashing water
• wind

Treatment:

• remove all infected parts
• clear ground of leaf and twig litter
• apply liquid copper fungicide to reduce recurrence

Prevention:

• prune plant to provide good air circulation and access to sunlight
• space plants to provide good air circulation
• remove and destroy infected fruit and branches (do not compost!)

Armillaria Root Rot

Cause: Fungus that weakens the wood

Symptoms:

• leaves are small and yellow
• upper part of bush has dead stems
• yellow mushrooms grow at the base of the bush in the fall
• white fungal growth on wood

How it Spreads:

• spores spread by rain, splashing water
• wind
• infection survives in wood debris and roots

Treatment:

• remove and destroy all infected plant parts
• clear ground of leaf and twig litter
• apply liquid copper fungicide to reduce recurrence

Prevention:

• remove and destroy infected plant parts, including roots and stumps (do not compost!)
• clear soil of all vegetation
• leave soil bare 1-3 years

Anthracnose

Cause: Fungus

Symptoms:

• leaves turn yellow at the tips, eventually turning brown all around
• browned, dying leaves
• dark, sunken lesions on fruit and/or stems

How it Spreads:

• spores spread by rain, splashing water
• wind

Treatment:

• remove and destroy all infected parts
• clear ground of leaf and twig litter
• apply liquid copper fungicide to reduce recurrence

Prevention:

• prune plant to provide good air circulation and access to sunlight
  provide proper water and fertilizer

Bacterial Canker

Cause: Bacteria

Symptoms:

• lesions on the trunk become red/brown or black cankers about an inch across
• cankers can extend the length of the stem and kill the plant

How it Spreads:

• bacteria enters through cuts in the wood

Treatment:

• cut off and destroy diseased stems
• clear ground of leaf and twig litter
• apply liquid copper fungicide in spring and fall to reduce recurrence

Prevention:

• sterilize all garden tools to avoid spreading infection
• when pruning, be careful not to damage the bush
• protect plants from frost

Botrytis

Cause: Fungus

Symptoms:

• leaf, stalk, and crown rot

How it Spreads:

• fungus overwinters in infected plant material
• rotting material near plants
• wind, insects, birds

Treatment:

• removed and destroy infected plant parts
• apply fungicide at first notice

Prevention:

• liquid copper fungicide
• keep rotting material away from plants
• plant disease-resistant varieties
• remove and destroy plant debris

Crown Gall

Cause: Bacteria

Symptoms:

• galls (bulges) on the plant, from the base of the trunk up through lower branches
• galls go from cream-colored to dark brown or black
• galls develop on wounds or pruning cuts on the plant

How it Spreads:

• bacteria present in ventilated soils (sandy loams)

Treatment:

• remove galls with a pruning knife
• seal all wounds on the plant
• if the plant doesn’t improve, remove and destroy it

Prevention:

• do not overwater
• plant bush shallowly — only a couple inches into the soil
• take care not to injure the plant
• seal any wounds/pruning scars promptly

Fusicoccum Canker (Godronia Canker)

Cause: Fungus

Symptoms:

• small lesions on new stems and buds
• lesions grow each year until they wrap the stems and kill the plant
• cankers start off reddish-brown, then turn gray in the middle with dark brown margins
• leaves of infected branches may turn brown earlier than normal in the fall

How it Spreads:

• develops during cool and wet weather, infecting plants through wounds or pruning cuts

Treatment:

• no fungicide is available to treat this infection
• remove and destroy all infected parts
• seal all wounds on the plant

Prevention:

• prune off and destroy infected branches
• avoid overhead irrigation; water at ground level
• grow resistant cultivars

Mummy Berry

Cause: Fungus

Symptoms:

• fungal masses resembling mummified fruit develop instead of berries
• infection shows up mostly in the lower stems
• wilting shoots and flower buds
• young leaves die off

How it Spreads:

• spores spread by rain, splashing water
• wind

Treatment:

• remove and destroy all infected plant parts
• lay down a layer of mulch in early fall or late winter
• apply liquid copper fungicide to reduce recurrence

Prevention:

• clean up area under and around bushes
• remove and destroy all plant debris from previous season
• use mulch to smother any remaining mummified fruit

Phytophthora Root and Crown Rots

Cause: Oomycetes

Symptoms:

• plants not thriving
• leaves turn yellow, then red, then collapse
• crowns exhibit black-brown decay
• large roots missing feeder roots
• larger roots have brown-black holes

How it Spreads:

• rain helps spread spores in temperatures between 65°-75° F.
• overwatering can spur crown rot

Treatment:

• remove and discard infected material

Prevention:

• buy or acquire healthy plant stock
• plant in well-drained soil
• remove and destroy infected plant material as soon as you discover it
• avoid planting in cool, wet weather
• avoid overhead watering; water at soil level
• make sure plants have good air circulation and lots of sun

Powdery Mildew

Cause: Fungus overwinters on infected plant debris and emerges in warm, humid weather

Symptoms:

• white, powdery patches on leaves
• leaves may curl and turn upward
• new shoots appear stunted
• older infections look like a tan or reddish-brown felt covering; these contain spores
• heavy mildew infections can stunt a plant’s growth

How it Spreads:

• fungus overwinters in infected plant debris
• spores do not need moisture to germinate; often called a “dry weather disease”
• wind, insects, birds

Treatment:

• removed and destroy infected plant matter

Prevention:

• liquid copper fungicide
• if necessary, sulfur-based fungicide
• plant disease-resistant varieties
• remove plant debris

Silver Leaf

Cause: Fungus

Symptoms:

• young blueberry leaves turn silver
• leaf color change can spread to the entire bush
• infected stems have a brown center with purple or brown concentric rings
• discoloration at the base of the trunk and infected branches

How it Spreads:

• spores from other infected plants spread by wind
• fungus spreads through cuts and wounds in the wood

Treatment:

• remove and destroy all infected plant parts
• no chemical treatment once plant is infected

Prevention:

• clean up area under and around bushes
• remove and destroy infected plants
• prune with care and seal all wounds with liquid pruning sealer

Witch’s Broom

Cause: Fungus

Symptoms:

• fungal mass at the base of the bush resembling a broom
• leaves stay small and do not develop
• shoots have reddish spongy bark

How it Spreads:

• fungus grows in the bark and spreads to the entire bush

Treatment:

• remove and destroy (burn) all infected plant parts
• no fungicide treatment is available
• pruning out the witch’s brooms can provide temporary relief

Prevention:

• remove and destroy (burn) all plant debris
• clean out all plant litter before planting a new bush
• do not plant figs and blueberries within 1,500 feet of each other; both are susceptible to infection

If you’re not sure what’s wrong with your blueberry plants, take good close-up pictures and contact your local garden center or extension center for advice. Many diseases present with similar symptoms, but the treatment for them may vary. In general, you can reduce the likelihood of fungal infections with careful, consistent watering. It’s not a failsafe, but it’s good gardening practice.

Which diseases have you had to treat on your blueberry plants? Please tell us how you prevent and handle diseases. If you spot other symptoms on your blueberry plants that are not mentioned here, contact your local extension center or garden center for a consult—and please let us know what you discover.