Blueberry Botrytis Blight Treatment – Learn About Botrytis Blight In Blueberries

Blueberry Botrytis Blight Treatment – Learn About Botrytis Blight In Blueberries

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By: Mary H. Dyer, Credentialed Garden Writer

What is botrytis blight in blueberries, and what should I do about it? Botrytis blight is a common disease that affects blueberries and a variety of other flowering plants, especially during extended periods of high humidity. Also known as blueberry blossom blight, botrytis blight is caused by a fungus known as Botrytis cinerea. Read on to learn more.

Symptoms of Botrytis Blight in Blueberries

Recognizing blueberry with botrytis blight can help some, but prevention is always the best line of defense. Blueberry blossom blight affects fruit, blossoms, and twigs. All plant parts can be covered with a hairy, gray fungal growth, and tips of shoots may appear brown or black.

Infected flowers take on a brown, water-soaked appearance, which can spread to the twigs. Unripe fruits shrivel and turn bluish-purple, while ripe berries are tan or pale brown.

Preventing Blueberry with Botrytis Blight

Plant blackberries in light, well-draining soil and ensure plants are exposed to direct sunlight. Also, provide adequate spacing to allow for air circulation.

Avoid overfeeding blueberry plants. Thick, lush foliage takes longer to dry and increases risk of disease.

Water blueberries with soaker hoses or drip irrigation systems. Irrigate in the morning to allow sufficient time for leaves to dry before nightfall.

Spread a generous layer of mulch around plants to create a protective barrier between the fruit and the soil. Reapply as needed. Practice good weed control; weeds limit air movement and slow drying time of blooms and fruit. Keep the area clean.

Prune blueberries when the plants are dormant. Remove old canes, dead wood, weak growth, and suckers.

Blueberry Botrytis Blight Treatment

As previously stated, controlling blueberry botrytis blight is best done through prevention. That being said, fungicides may be effective when used in conjunction with the above preventive steps. Consult your local cooperative extension office for detailed information.

Use fungicides judiciously, as the fungus that causes blueberry blossom blight may become resistant when fungicides are overused.

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Blueberry plants (Vaccinium spp.) are native to eastern North America, although they can be grown in any cool to mild weather climate in U.S. Department of Agriculture hardiness zones 3 through 10. Like many plants, blueberries can suffer from problems caused by pests and diseases. Regular pruning, good harvesting techniques and proper disposal of leaves and plant debris help to prevent disease in blueberry plants. In some cases, use of a fungicide also may be required.

MSU Extension Blueberries

Freezes and disease cause similar symptoms on blueberry plants. Here is what to look for in your field.

Photo 1. Young shoot tip killed by a freeze. Photo by Mark Longstroth, MSU Extension.

We are three weeks past the May 9, 2020, freeze that hit southwest Michigan. Growers have been evaluating flowers for freeze injury. Besides damage to blossoms, we see dead shoot tips and damage to the tips of new shoots from the freeze. We are also seeing disease symptoms in shoots and twigs. Blighted tissue is apparent in many fields. This damage manifests as twig, blossom and cane blights. These blights may be due to the freeze, disease or a combination of both. The weather has turned warm and wet, causing blueberries to grow rapidly. Warm, wet conditions are also good for disease infections. When scouting fields, keep in mind the following:

  • Death of the new shoot tip, which stops growth, is usually a symptom of a recent freeze (Photo 1).
  • Death of the new shoot is a symptom of mummy berry shoot strike.
  • Dieback of the woody shoot tips and blighted blossoms are usually symptoms of several different diseases.

Several fungi and a least one bacterium can cause blight symptoms in blueberry tissues. These diseases are often hard to distinguish from each other on symptoms alone (see table below).

Disease (causal agent)

Shoot blight (Yes/No)

Blossom and early green fruit blight (Yes/No)

Anthracnose (Colletotrichum acutatum)

Botrytis blight (Botrytis cinerea)

Mummy berry (Monilinia vaccinii-corymbosi)

Phomopsis blight (Phomopsis vaccinii)

Pseudomonas canker (Pseudomonas syringae)

Colletotrichum (anthracnose) and Botrytis are often the cause of infections during wet seasons. The cause of blighted shoots and blossoms is difficult to identify unless fungal growth is visible. Blighted blossoms can also be caused by Phomopsis. Phomopsis can be identified by a brown discoloration of the twig that bears the flower cluster (Photo 2). Blighted leaves are often blamed on Botrytis infections during extremely wet conditions.

Photo 2. Phomopsis blossom blight. Photo by Timothy Miles, MSU Department of Plant, Soil and Microbial Sciences.

We have received many blueberry samples with blight symptoms and pathogens present. Many can be traced back to freeze damage that occurred earlier in the season.

  • One sample had characteristic anthracnose symptoms on shoot tissue (Photo 3). This sample was of shoot dieback that occurred last year, and Colletotrichum (the fungal pathogen) had overwintered in the infected tissue.
  • We have also received pictures of shoot blight where flower buds failed to open, and we suspect it to relate back to freezes in mid-April (Photo 4).
  • Finally, we have received samples where leaves grew briefly but then became blighted and died. This looks similar to a mummy berry infection, but no characteristic conidia were observed. This also was likely related to early season freeze damage (Photo 5).
Photo 3. Blighted shoot tissue with characteristic anthracnose symptoms on shoot tissue. Photo by Mark Longstroth, MSU Extension. Photo 4. Blighted bud tissue of blueberries observed in late May, likely caused by freeze events. Photo by Mike Reinke, MSU Extension. Photo 5. Blighted leaf tissue observed in the Muskegon area this season, likely caused by early winter damage but several plant pathogens recovered from this tissue. Photo by Laura Miles, MSU Plant & Pest Diagnostics.

If you want more information about your blighted samples, you need to submit actual samples to Plant & Pest Diagnostics at Michigan State University for a positive identification.

Control methods for blighted tissue

Chemical options

Controls are the most effective if they are applied prior to blight infections. Pseudomonas canker is caused by a bacterium and fungicides do not control bacteria. No antibiotics are registered in blueberries. Early sprays of copper can reduce bacterial canker. Target it early next spring, not now after bloom.

Research on anthracnose and phomopsis blight has shown that most twig blight and blossom infections occur at bud break. Many fungicides have good activity against mummy berry and phomopsis blight. Colletotrichum infections require warm and wet conditions. They can occur before, during and after bloom. Bloom and post-bloom fungicide spray target these infections.

As we transition from pre-bloom to post-bloom disease control, careful choice of fungicides to control the disease is important. Several fungicides are rated good to excellent at controlling the various fungi that cause twig blight. MSU Extension annually updates the Michigan Fruit Management Guide (E0154). This resource has good information about fungicide choices based on disease and fungicide effectiveness. We recently posted an updated list of fungicide efficacy against anthracnose and alternaria fruit rot. For more information, refer to “Blueberry growers need to focus on anthracnose fruit rot as bloom ends.”

Other control methods

In addition to chemical options, there are several cultural control strategies you can deploy. Mainly, you are trying to reduce sporulation by 1) minimizing overhead irrigation and 2) timing irrigation to coincide with natural dew formation.

This article was published by Michigan State University Extension. For more information, visit To have a digest of information delivered straight to your email inbox, visit To contact an expert in your area, visit, or call 888-MSUE4MI (888-678-3464).

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Cooperative Extension: Maine Wild Blueberries

I think the mummy berry infection season is now over for 2014. Any remaining cups would have dried up over the last few days, so there won’t be any spores to infect the plants. I don’t think the wet weather we had this weekend or will have on Tuesday will be causing any infection periods for the mummy berry fungus.

You may be seeing symptoms of Mummy berry disease in your field now and over the next week. It is too late to spray fungicide at this time. Any symptoms you find are from infections that occurred at least nine to ten days ago. The spores produced on the dead leaves and flowers will NOT cause new killing infections. These spores will infect healthy flowers and produce mummy berries. The number of mummy berries produced is typically too low to be concerned about trying to control this stage of the disease.

Mummy Berry Symptoms

Symptoms of mummy berry disease are shown in the pictures below. This fungus does attack and kills both flowers and leaves. Flowers are typically killed before they open. The petiole (base of leaf) of leaves give a characteristic shepherd’s crook shape. Powdery gray spores can be seen at the base of the leaves or flowers where they attach to the plant. Unless it is a very susceptible clone, you will only see isolated leaves and flowers with the disease.


Frost has been minimal this year but may occur in hollows or some more sensitive clones. Frost tends to affect most of the flowers on a stem. You may also see just the green growing tip of the leaf dying off. Please see pictures below.

Botrytis Blossom Blight

You may see Botrytis blossom blight occurring in your field if you had some bloom last week. The weather over this weekend only produced conditions for Botrytis infection at our North Ellsworth and East Machias/Whiting weather station locations. Fields in this area are at risk of Botrytis infection IF the fungus is in these fields. You can scout for this disease in early blooming clones or dying tissue on weeds in the field. The symptoms are dead, open, flowers with black hairs sticking out of them (see picture below). You will probably need a magnifying glass or hand lens to see the hairs.

ONLY apply fungicides to control Botrytis blight IF

  1. you have seen severe infection this year in early clones, this means more than one or two blossoms affected, and
  2. you have had a severe problem with Botrytis blossom blight in previous years.

You will want to minimize any exposure of honey bees, bumble bees AND native pollinators to pesticides, including fungicides, during bloom. Bumble bees and native pollinators will still be working pollinating your fields when poor conditions keep the honey bees in their hives. The fungicides recommended for control of Botrytis blossom blight are considered non-toxic to honey bees BUT we do NOT know how native pollinators would react to these materials or how there may be subtle effects on honey bees and bumble bees.

My recommendation is NOT to apply fungicides to control Botrytis blossom blight unless you are SURE you have it in your field. In my experience visiting many fields reported to have Botrytis blossom blight is that the dead blossoms have been due to Mummy berry disease in the majority of fields.

If you do apply fungicides during bloom, apply them at LATE EVENING or at NIGHT to minimize the exposure of pollinators to these compounds.

Botrytis infected flowers showing black “hairs” with spores

Any questions please call Seanna Annis at 1.800.897.0757 (Maine only), or email at [email protected]

Watch the video: Spring Rose Diseases - flowers rotting botrytis