Bee Health

How does NRCS potentially enhance Bee Health?

NRCS has developed a number of plant-based, water extracts which have shown very effective results in controlling, and eradicating, both bacterial pathogens that are the cause of American Foulbrood (AFB) and European Foulbrood (EFB) in laboratory tests.

These plant extracts are known to be harmless to adult honeybees but have shown remarkable effects against both the biofilm, and the endospores of Paenibacillus larvae, the pathogen responsible for AFB, and the bacterial pathogen, Melissococcus plutonius, responsible for EFB.

NRCS believes these extracts will counter the growing resistance being shown by these pathogens to the standard antibiotics such as oxytetracycline and tylosin, currently being used for control. At the same time, eliminating the use of these antibiotics will allow for potential production of “organic” honey products by the industry. NRCS has begun a study on the potential control of the varroa mite (Varroa destructor) by these same extracts. The supposition is that these extracts contain compounds with miticidal properties, as well as compounds with antibacterial properties. Preliminary results are encouraging.

What are the current challenges?

Colony collapse has been a major challenge. The Canadian Association of Professional Apiculturists. Statement on Honey Bee Wintering Losses in Canada (2021-2022) reported that hive losses were 45.5% of hives operated in 2021, based on the survey responses received (46.6% of beekeepers contacted).

Antibiotic resistance against the foulbrood pathogens and the varroa mites is emerging, presenting another major challenge to bee health.

Other major challenges to bee health are outlined as follows:

1. Paenibacillus larvae (American Foulbrood)

American foulbrood (AFB) is the name given to a disease that results in the decimation of the honey bee larvae and the eventual collapse of the colony. The condition is caused by a pathogen, Paenibacillus larvae, a gram-positive bacterium. Only honey bee larvae are affected by this pathogen.

The bacterium has several defense mechanisms that shield it from the normal control agents, such as the medically important antibiotics like oxytetracycline, lincomycin and tylosin. These mechanisms include its ability to form biofilm and endospores.

Biofilm, in simple terms, is a thin, slimy film of bacteria and bacterial secretions that physically attaches itself to surfaces and is difficult to completely eliminate. The biofilm provides protection to the bacteria that live within it and make it difficult for control agents to penetrate and eradicate the bacteria. It also protects the bacteria from harsh environmental conditions.

This bacterium also has the ability to form endospores. To quote from the Symbiosis website (

“Endospore – A differentiated cell formed within cells of certain Gram-positive bacteria that are extremely resistant to heat and other harmful conditions and agents.

Endospores are the resting stage during the life cycle of some bacteria, formed in response to adverse conditions. The bacterial cell changes into a partially dehydrated core, enclosed in a multilayered protein coat. On return to favorable conditions the spore germinates and reverts back to the normal vegetative form of the organism and continues its life cycle.

Endospores can remain viable for long periods of time, potentially thousands of years.”

The endospores of Paenibacillus larvae can remain viable for up to 40 years. The endospores can be spread through an entire area by foraging bees, or contaminated honey from an infected hive, or by contaminated tools or equipment used in a contaminated hive.

The endospores are the main pathway to infection of the honey bee larvae. The endospores enter the brood chambers before they are sealed through contaminated food or contact with bees carrying the endospore. The critical period for larvae infection is 12 to 36 hours after egg hatching. The bacteria emerge in the larva’s gut and begin feeding on the body tissues eventually killing the larva.

American foulbrood is a global problem for apiculture. Control and eradication of the pathogen presents real challenges. Evidence of antibiotic resistance to the common control agents has emerged. The endospores are resistant to heat and to the most commonly used disinfectants. The most effective means of control at the moment is burning infected hives.

2. Melissococcus plutonius (European Foulbrood)

European Foulbrood (EFB) is the name of a disease caused by the gram-positive bacterium, Melissococcus plutonius, that results in an effect similar to that seen from American foulbrood on the larvae of honey bees (Apis mellifera). Like Paenibacillus larvae, Melissococcus plutonius does not harm adult honey bees but only infects the larvae. It is also known to infect the Asian honey bee (Apis cerana).

Contamination of the hive will occur through routes similar to that of Paenibacillus larvae infection, entering uncapped brood chambers. But unlike Paenibacillus larvae, Melissococcus plutonius does not produce endospores, nor is it known to produce a biofilm. Control methods for EFB use the “Shook swarm” method or antibiotics such as oxytetracycline.

EFB like AFB, is also a global problem for apiculture. The re-emergence of EFB in Canadian bee hives may signal that strains of Melissococcus plutonius may be developing antibiotic resistance as well.

3. Varroa destructor (Varroa Mite)

Varroa destructor is an external parasitic mite that attacks and feeds on the honey bees, Apis mellifera and Apis cerana. The disease caused by these mites is called varroosis. The varroa mite can reproduce only in a honey bee colony. It attaches to the body of the bee and weakens the bee by sucking on its fat bodies.

A male mite can mature in 5-6 days after hatching; a female in 7-8 days Females can lay a fertilized egg every 30 hours on bee larvae.

NRCS Extract Kill Rate of Bee Pathogens and Mites

NRCS Extract Kill RatePaenibacillus larvaeMelissococcus plutoniusVarroa destructor
Planktonic cells / arachnids100%99.99%Average 60%***

*Melissococcus plutonius does not form rigid biofilm nor endospores
**Varroa destructor is an arachnid and does not form biofilm or endospore
***Based on preliminary data

Use of plant extracts as an alternative, novel, and natural agent for the treatment of Canadian bee colonies affected by foulbrood diseases. Joe Ross, Ph.D. and Gerard Bedie, Ph.D.