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How to Protect Honey Bees During Blueberry & Cranberry Pollination

Updated: Oct 5, 2023

There are many challenges that honey bees and commercial beekeepers face as they enter the season of blueberry and cranberry pollination. We’ll explore why there is a higher incidence of EFB (European Foulbrood) disease during and after pollination. As well as blueberry nectar and pollen's effect on the hive as a food source. Join us as we reveal some of the details about why probiotics containing LAB (Lactic acid bacteria), Bacillus, and Pediococcus, such as SuperDFM+P801, improve honey bee survival during the toughest pollination contracts.


• Pollinating Cranberries and Blueberries

• Are honey bees good at pollinating blueberries and cranberries?

• Are honey bees suffering from EFB during blueberry pollination?

• Why Vaccinium pollination is challenging for honey bees.

• Probiotic bacteria help digest pollen.

• Blueberry pollen has a high pH.

• What helps bees digest high-pH pollen?

• Are fungicides used in blueberry fields killing honey bees?

• Fungicides are not harmless to bees.

• How can beekeepers mitigate losses from blueberry pollination?


Pollinating Cranberries and Blueberries Commercial beekeepers consciously prepare their bees to meet the challenges of pollinating important commercial crops like blueberries and cranberries months before the hives are in the field. In the U.S., cranberries and blueberries bloom from May to early July. Are honey bees good at pollinating blueberries and cranberries? Interestingly, honey bees are not the most efficient pollinator of blueberries or cranberries. In fact, bumble bees who utilize “buzz-pollination” are better equipped for pollinating these bell-shaped blossoms of the Vaccinium genus. However, honey bees are often used due to the fact that they are more reliably available and provide the massive numbers required for most pollination needs. Therefore, honey bees are regularly used alone or combined with bumble bees to pollinate cranberries and blueberries in North America. While native bees and bumble bees are naturally more inclined to pollinate these bell-shaped flowers, their native populations don't have sufficient numbers to handle agricultural needs. Without sufficient pollination, the fruit will not set and will not reach its ideal size. Honey bees are responsible for 90% or more of blueberry and cranberry yields. Are honey bees suffering from EFB (European Foulbrood) due to blueberry pollination? Yes, but it’s complicated. One of the challenges that beekeepers face in pollinating blueberries and cranberries is the high incidence of European Foulbrood (EFB) disease both during and after pollination. Sometimes, honey bee colonies are so weakened by blueberry pollination that they take months to recover. This negatively affects their following pollination contracts and honey production. A 2016 study of honey bee colonies pollinating blueberries and cranberries found that these crops had specific and significant effects on the brood and colony health. Blueberry pollination decreased the surface of capped brood, while cranberry pollination decreased colony weight. These effects were crop specific and persisted after the colonies were moved from the pollination fields to their home apiaries. At the same time, the evidence did not show specific increases in Nosema, Varroa, or virus transmission among honey bee colonies during pollination. This study points out that the EFB outbreaks following blueberry pollination are linked to the increased vulnerability of honey bee colonies during this treacherous time due to stresses such as a shortage of nurse bees, cold and damp weather, and poor nutrition rather than the increase in pathogens. These conditions during Vaccinium pollination make honey bee colonies susceptible to EFB disease.

Why Vaccinium pollination is challenging for honey bees.

It’s important to know that blueberry and cranberry blossoms are less beneficial for honey bees due to their relatively low nectar reward. This is why commercial beekeepers will provide sugar syrup for their hives during these contracts; to mitigate nectar scarcity. Additionally, the amount and quality of pollen protein brought in by foragers is insufficient to support brood rearing and limits the development of the hive’s immunity against parasites and pathogens.

cranberry flowers in bloom

Blueberry pollen has a high pH. Pollen composition varies significantly between different plant sources, and many factors influence the value of nutrition that the pollen provides. In his dissertation, Dr. Gordon Wardell implicated the higher pH of cranberry pollen (pH 6.2) and blueberry pollen (pH 6.0 – 6.4) in the increase of EFB disease. pH is a measure of acidity in any food or substance. Dr. Wardell's reasoning is that it is more difficult to digest these pollens because of their high pH (aka, low acidity). What helps bees digest high-pH pollen? Animals normally maintain a low pH in their stomachs (think stomach acid), and this acidity helps them to break down the food. When bees consume high-pH pollen, it increases the pH in their digestive tract and slows down or stops the digestion process. Poor digestion and, therefore, poor protein absorption make the nutritional deficiencies worse. Bacteria normally present in the honey bee environment play an important role in the digestion of pollen protein. Lactic acid bacteria in the digestive tract produce lactic acid, and lactic acid lowers the pH back to the point that is healthy for digestion. In Dr. Wardell's dissertation, adding lactic acid to the bees' diet mitigated EFB. Another way to counteract high pH and digestive problems arising from blueberry or cranberry pollen is to add lactic acid bacteria to the bees' diet. Fungicides and other anti-microbial substances that kill bacteria, along with sterilized honey bee food, can result in a lack of normally occurring bacteria during times of stress and pollination. Honey bee probiotics, such as SuperDFM and SuperDFM+P801, deliver a highly concentrated dose of probiotic bacteria to speed up digestion and facilitate pesticide detoxification. Probiotic bacteria produce lactic acid, which acidifies (or lowers) the gut's pH.

Are fungicides used in blueberry fields killing honey bees? Blueberries and cranberries grow in wet, cold environments. Therefore, growers use a lot of fungicides. To learn more about the effects of fungicides on honey bees, researchers in Saskatchewan decided to run some tests. Their study reported the effects that fungicides (commonly used in blueberry production) have on honey bee larvae infected with EFB disease. Unexpectedly, the study found that one, two, or three fungicides have no effect or even positive effect on the health and survival of honey bee larvae infected with EFB. However, when four commonly used fungicides were combined, it did cause an increase in the death of honey bee larvae.

Fungicides are not harmless to bees.

Growers work to coordinate fungicide applications and may not be spraying four fungicides in one week, although tank mixes are frequently used. It’s important to note that even if four fungicides are not used in one field at one time, honey bee colonies accumulate fungicides in the pollen they harvest and store it in their bee bread. In fact, according to a USDA study, almost all (98%) of honeybee comb and foundation wax in North America are contaminated with an average of 6 different pesticides per sample. Additionally, if adjacent fields receive different chemicals, honey bees can forage on them, and this results in combined fungicide loads in the hive. As research shows that an increased number of chemicals (fungicides) increases toxicity and effects on honey bee larvae, using fungicides is not harmless to honey bee colonies, as was previously thought.

How can beekeepers mitigate losses from blueberry pollination?

A risk management strategy should be taken into consideration. Discussion among beekeepers and farmers may help to evaluate the increased pollination costs for these unique crops, which could help beekeepers appropriately support honey bees through these challenging fields. Blueberries and cranberries are difficult crops for pollinators, partly due to the fungicides used and partly due to the distinct features of their flowers, nectar, and pollen. Knowing this, beekeepers need to support their hives with supplemental feed proactively. However, it's important for beekeepers to understand that pollen patties and sugar syrup are sterile and do not include the live-active microbial forces that will help lower pH and increase digestion and nutrient absorption. Supporting your hive's microbiome before, during, and after pollination with probiotics like SuperDFM+P801, which was specifically formulated to help bees activate their detoxification of pesticides, offers beekeepers an important tool to shield their bees from the toxicity of the many fungicides used in blueberry and cranberry fields. It’s important to do your research as you formulate your risk management strategy and talk with other beekeepers to learn from their experience. If you’d like to hear more about what beekeepers are saying about SuperDFM, check out some of our testimonies.

SuperDFM® Probiotics

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