How to Treat Mummy Berry in Blueberries: A Complete Guide for Growers

Be vigilant of mummy berry on blueberries as soon as early spring until they are in fruit. Fungus Monilinia vaccinii-corymbosi infects the young portions of blueberry shoots, leaves, flowers and fruit. Mummy berry does not hinder fruit setting, but will cause some fruit to be unmarketable as the disease advances.

Cooler wet weather in spring is a favorable condition for the disease. The fungus produces and disperses spores in moist conditions and infectable young tissue is present. This is why waiting until I observe that the berry has been damaged isn't a good option for how to treat mummy berry in blueberries. At this time, infection has occurred.

This mummy berry disease is named for its most obvious fruit symptom, the appearance of a mummy. Infected berries fail to develop normally, turn brown, shrink and develop into hard, wrinkled objects more like mummies. They can persist in or under the canopy of a plant and cause new infections in the next growing season.

The vial important part to the gardener is that mummy berry infects during the spring and then infests the fruit during the later stages. An early diagnosis means that I have more time to do sanitation and monitoring and take proper disease management measures when necessary to limit disease distribution.

Mummy Berry Symptoms: What I Look for in My Blueberry Plants

Sometimes the first symptoms may appear on younger shoots and leaves instead of on the berries. Newly infected shoots can wilt, turn brown and develop a characteristic curved appearance. As the fungus invades the leaf tissue, browning and discoloration of young leaves may occur.

In particular, the symptoms of developing berries are very characteristic. Infected fruit may turn light in color—pale, pink, tan, or reddish—and instead of developing as expected, may bloom prematurely.Infected fruits may turn pale, pink, tan or reddish in color, and develop before their time. They may develop an unusual appearance and eventually shrivel, harden and become dark, wrinkled mummy berries.

This sequence enables me to tell the difference between mummy berry and insect, nitrogen deficiency and other mummy berry damage disease issues. Not all symptoms, however, are associated specifically to dothiorella, therefore, when dealing with an unfamiliar issue, fruit condition should not be the only diagnostic criteria used.

Wilted young shoots in spring and abnormal and discolored berries later in season are important clues to consider when mummy berry is a possible diagnostic consideration.

The life cycle of Mummy Berry Disease (MBD) is important to understand

With knowledge of the mummy berry disease life cycle control is much easier because the disease simply isn't present on the berries during harvest. It persist from one season to another and has a series of stages of infection.

The cycle starts with the tough, dry fruits of the former season. The following winter these mummies can overwinter on or under blueberry. Under favourable spring growth conditions, the mummies may develop small cup-shaped apothecia.

Airborne ascospores are spread out from these apothecia. In favorable wet weather between the bud break stage and bloom, the spores are able to infect any developing blueberry shoots and leaves that are susceptible. It is an important time for primary infection.

Infected plant tissues will then form more spores, called conidia. The spores can be shared while flowers are in bloom and infect blueberry flowers. Infected flowers can develop in the characteristic mummy with eventual infection of the developing fruit.

To my man in the garden mind, every step affords me another chance for management. Now when I'm in dormancy, I can be dedicated towards sanitation. I can search for apothecia as well as watch the weather in the early spring period. I can expend energy to protect vulnerable fruit rather than waiting for the mummified fruits to become visible around bud break and bloom.

That's why I see mummy berries more easily managed prior to heavy fruit symptoms.

Should I spray on Mummy Berry, on Blueberries?

The optimum time for a mummy berry treatment is normally prior to the occurrence of the disease in mature fruit. When I see many hard shrivelled berries the cycle of infection has gone a long way.

I begin to notice in early spring, notably at bud break. The weather conditions are important because the fungus has to have the right moisture to produce spores and infect susceptible parts of the plant. Occurrence of rainfall during critical development stages can thus cause a threat of infection.

As the plants approach flowering, monitoring can be of particular importance. There are two levels of infection: primary in youthful tissue and secondary in flowers, and this provides a different opportunity for disease management. Typically, extension recommendations are based on fungicide applications during these sensitive growth stages, as opposed to applications once fruit symptoms are observed.

Also, there should be adjustments to how close I go to scout, according to the weather. A cool wet spell when it is in bud break or in bloom should be given special consideration than a long period of dry. But I shouldn't simply leap to conclusions based on the weather. Management decisions on the need for treatment and timing should be based on local disease decisions and extension recommendations as well as product label regulations.

As such, my strategy for treating mummy berry in blueberries is one of prevention: recognize how to treat mummy berry in blueberries, keep an eye on susceptible stages of crop growth and apply any treatment approved at the recommended time and place for my product.

Mummy Berry Control: Start With Garden Sanitation

First, what I can do for the control of mummies is to have good sanitation. None of the dried berries are just random filth or waste; they can be the beginning of the next episode of disease.

Fallen and overwintered mummified berries are removed from under blueberry shrubs wherever possible. Hand pulling and raking may be practical solutions in a small garden. This is done to minimize the resources of infected material that can be used to create apothecia in spring.

It is also possible, depending on the planting system, to reduce the soil surface spore production by the mummy by cultivation or burying of infected berries. Another physical barrier can be mulching to cover mummies and inhibit their ability to produce/spread spores.

I also consider the blueberry planting structure. Excessive bushiness may increase the difficulty of airflow inside the plants and traffic moisture inside the leaves and flowers. Canopy management through pruning and plant spacing may be useful in producing a more open and dry canopy.

Lastly, I don't leave the leaves wet any longer when it is not necessary. However, good irrigation practise can help to minimise extended leaf wetness periods, except that irrigation cannot be excluded in areas where the plants leave require water and it provides them!

While sanitation is not a means to guarantee eradication of mummy berry, it does help to decrease primary inoculum and assist in other management efforts if disease pressure is high.

Removing Mummy Berry from Blueberries Naturally

How to get rid of mummy berry on blueberries? If water soluble 4-diroids are the only alternative to all conventional fungicides, then an integrated approach is my way to go to diagnose and decide how to eliminate mummy berry in blueberries.

First, I take out as many mummified berries as I can and clean under the plants. Then I keep observing the bushes in spring for any sign of disease and am mindful of any weather conditions that might facilitate infection. Wherever possible, selecting blueberry cultivars that have useful disease resistance increases can be a part of a long-term strategy.

Other tools can exist alongside the biological disease-management products. A useful organism of interest is a beneficial bacterium known as Bacillus subtilis which has been studied for its allelopathy against plant pathogens. It has been observed to colonise plant surfaces and compete with disease-causing microorganisms, and can also be detected to make antimicrobial compounds that can contribute to pathogen suppression.

The biocontrol agent B. subtilis has been specifically studied for blueberry mummy berry management. Biological activity against Monilinia vaccinii-corymbosi has been reported from blueberry flowers and B. subtilis shows promise as a component of an integrated disease-management program.

The fact that it has allowed gardeners to consider an organic mummy berry control makes Bacillus subtilis a very interesting bacterium. I would use it as a preventative biopesticide though, and not as a remedy for mummified berries.

The other biological fungicide to be considered is from Novobac which has a product registration and label that specifies intended crop and disease control. According to the product information B. subtilis has microbial biocontrol activity and is considered by the product information as microbial, plant colonising and pathogen suppressing.

However, the key point is that there is a time element required for natural/biological management. Combined preventive removal of inoculum, monitoring, and using the right biological product can be more effective than preventing the severe symptoms.

What Gardeners need to know about the best fungicide to use to control mummy berry?

The best fungicide for mummy berry would not assume that the product is necessarily always the best option for all blueberry plantings. The treatment of the appropriate and the factors of products registered, disease pressure, weather, susceptibility of the cultivar, and local recommendations are all factors to consider.

Pesticides for managing mummy berry will best protect the crop if applied before or during the periods in which the fungus is capable of infecting the crop, not after the fruit has mummified. Important local timing can be around bud break and flowering.

Biological fungicides that include other organisms such as Bacillus subtilis, may be used, if available and labelled for the corresponding crops and diseases. They are not the same products that are generally used for fungicide treatment and may be managed in an integrated mummy berry disease management program.

When I am using conventional fungicides more frequently I consider fungicide mode of action as well. If recommended, rotating products with different mode(s) of action can help alleviate fungicide resistance selection pressure.

The most important thing, I now look at the current label before applying any product and see my location. Label directions specify registration status for blueberries and specific disease, application rate, when to apply, restriction on harvest, and other instructions.

So, instead of asking "which fungicide do you prefer is the best," I would ask myself, "which registered treatment is best suited for my disease pressure, growth stage and local mummy berry management recommendations?

How to Treat Mummy Berry in Blueberries: My Seasonal Control Plan

So the answer to how to treat mummy berry in blueberries begins before the growing season and continues until they are harvested. The objectives of this are to break the disease cycle at multiple stages rather than a single treatment stage.

When it's not growing, my main concerns are sanitation. I am looking for apothecia and weather which may be conducive to spore discharge in early spring. I apply any registered preventive material at a time around the time of bud break (as recommended locally).

After my guess at blooming I keep watching since infected flowers may be a beginning source of mummy. I use biological products (e.g. Bacillus subtilis) if they are included in my disease-management strategy as directed on the crop information sheet and disease-management recommendations.

Post harvest I come back to sanitating. The residual mummified berries can cause problems the following season and so removing them is advantageous.

The biggest thing I was able to take away is that if I can identify this early, sanitary practices and timely preventative mummy berry treatment, I have the highest probability of lowering mummy berry control pressure. Once the fruit has been infected and is turning to hard mummies, my attention now turns to getting the mummies to stop contaminating the next disease cycle.

Reference:

• Ngugi, H. K., et al. "Effect of flower-applied Serenade biofungicide (Bacillus subtilis) on pollination-related variables in rabbiteye blueberry." Biological control 33.1 (2005): 32-38.
• Scherm, H., et al. "Biological control of infection of blueberry flowers caused by Monilinia vaccinii-corymbosi." Biological control 29.2 (2004): 199-206.