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Section V · Chapter 26

Reading the Brood: Disease Diagnostics and BC Reporting

American foulbrood and the rope test, European foulbrood, chalkbrood, sacbrood, nosema and the parasitic mite syndrome that imitates all of them — plus what British Columbia law requires you to report, and to whom.

14 min read · Mark Vanderende, Master Beekeeper

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Learning Objectives

  • Work a diagnostic sequence on a suspect brood frame instead of guessing from a photograph.
  • Perform and interpret the AFB rope test, and know what a positive one obliges you to do.
  • Distinguish EFB from AFB, chalkbrood from sacbrood, and all of them from a failing queen or chilled brood.
  • Understand nosema (Vairimorpha) as a gut disease with no visible brood sign, and when a sample is worth sending.
  • Recognise parasitic mite syndrome — the varroa-and-virus picture that mimics foulbrood.
  • Meet British Columbia's registration, reporting and notifiable-disease obligations under the Bee Act.
  • Sterilise, irradiate or burn equipment correctly, and stop a disease at one hive instead of a yard.

Read these first

This chapter assumes the ground covered below. If any of it is unfamiliar, take the detour — the sequence exists so nothing here has to be taken on faith.

Reading mode

Every beekeeper eventually stands over a frame that looks wrong and feels the specific loneliness of not knowing what they are looking at. Sunken cappings, a smell that is not quite honey, a pattern that has gone from wall-to-wall to shotgun in three weeks. This chapter exists so that moment becomes a procedure instead of a panic. The brood frame is the colony's medical chart. Adult bees hide their problems well and die away from home; the brood cannot, and it records everything that has happened in the last three weeks.

Work in order. Look before you touch, touch before you conclude, and conclude before you treat. Most beekeepers reverse that sequence and treat a diagnosis they never made, which is how a yard ends up medicated against something it does not have while the actual problem — nine times out of ten in this valley, varroa and the viruses it carries — keeps going.

The diagnostic sequence on a suspect frame

  1. 1Position the frame with the sun over your shoulder so light falls to the bottom of the cells. You cannot diagnose brood in shadow.
  2. 2Read the pattern first, from a metre back. Solid and even, or shotgun? Is the empty space scattered through capped brood, or is it a clean ring the queen simply has not reached?
  3. 3Read the cappings. Healthy cappings are dry, slightly convex, uniformly tan. Note anything sunken, darkened, greasy-looking, perforated or chewed at the edge.
  4. 4Read the larvae. Healthy open brood is pearly white, C-shaped, glistening, segmented, lying in a pool of royal jelly. Note anything yellow, brown, melted, twisted in the cell, or dried to a scale.
  5. 5Smell — deliberately, once, close. Healthy brood smells of warm wax and honey. Foul, sour, or 'old glue' smells are diagnostic information, though never on their own.
  6. 6Do the rope test on any sunken, perforated capping. Ten seconds with a matchstick answers the most serious question you will ever ask of a hive.
  7. 7Only then check the adults: crawling bees, K-wings, deformed wings, shiny hairless bees, dysentery streaking on the front of the box.
  8. 8Write it down before you close up. Frame number, side, what you saw. Photographs help the inspector; a written note helps you.

Watch — Guelph HBRC

Varroa Mites, Nosema Disease and Viruses — Dr. Ernesto Guzman

What to watch for — This is the single best free lecture on the varroa–virus–nosema complex from a Canadian research perspective. Watch specifically for how the symptoms of virus load overlap with what beekeepers call 'a disease problem'. Most of what gets reported to me as foulbrood is this picture instead.

University of Guelph HBRCOpen resource →
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Student chapter

The rest of this chapter is behind the hive gate.

You are reading the open preview of "Reading the Brood: Disease Diagnostics and BC Reporting". The full chapter — about 14 minutes of it, the beginner and advanced sidebars, the printable field cards and the paired Guelph video work all sit behind a Hive Key.

What a Hive Key opens

  • Every chapter in full, both reading tracks
  • Printable field cards — mite thresholds, feed schedule, queenright
  • The Guelph HBRC video library, paired chapter by chapter
  • The Princeton season dashboard, twice a month

How to get one

Hive Keys are issued to Hive Awakening students. Book a seat at the Princeton apiaries and your key comes with the confirmation — Tier 1 for the Beginner Masterclass, Tier 2 for the Master's Apiary.

See the 2027 workshops →

Track your way through the curriculum

Students with a Hive Key get completion ticks, percent-through-track and a resume button across every chapter.

Open the student desk →

From Section VTroubleshooting, Remedies & Field Hacks

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Watch alongside this chapter

From the Guelph Honey Bee Research Centre

Watch — Guelph HBRC

Diagnosing Brood Diseases — Foulbrood, Chalkbrood & Sacbrood

What to watch for — Watch the frame-handling more than the pathology: light over the shoulder, frame tilted so the sun reaches the cell floor. Half of all misdiagnosis in this valley is a frame read in shadow. Then compare their rope test to the seven-step version in our diagnostics chapter.

University of Guelph HBRCOpen resource →

Watch — Guelph HBRC

Apiary Disease Inspection & Sterilising Equipment

What to watch for — Note every point where a tool, glove or frame crosses between colonies. That crossing is the entire epidemiology of American foulbrood. Their scorch-and-irradiate protocol matches what a BC inspector will ask of you.

University of Guelph HBRCOpen resource →
Full video library →

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