3.18 - Causes, signs, treatment of other brood diseases

Question 1

What type of pathogen is chalk brood? 1

Answer 1

Fungus

Question 2

What does chalk brood affect 1

Answer 2

Chalk down death after capping

Question 3

When is chalk brood most likely to flare up and why 2

Answer 3

1. Typically flares up in Spring when colonies are expanding
2. If there are spores in the hive, and larvae are mildly chilled to 30˚C, brood becomes more susceptible
3. Spores infect the brood from contaminated worker mouth parts and germinate in the hind-gut of the larva

Question 4

How long is chalk brood infective

Answer 4

Condition endemic and spores infective for 3+ years

Question 5

Chalk brood signs 5

Answer 5

1. Affects sealed brood - perforated cappings
2. Mummified white larvae with mouth parts forming characteristic protuberance in centre. Often take on hexagonal shape of cell before shrinking, at which point bees removed them.
3. Mummies on floor out outside hive; easily shaken out, leaving pepperpot
4. Chalky mummy turns grey to blacks as fungus sporulates

Question 6

Chalk brood lifecycle 6

Answer 6

1. Larva ingests spores it with its food.
2. Needs COOL to germinate 30˚C, and CO2 of hindgut
3. So on pupation the spores germinate in hindgut.
4. Hyphae (threads) grow through gut wall, body and cuticle to produce a mycelium, a swollen mass of fluffy white fungus with small yellow lump where head used to be.
5. Mummy turns from white>grey>black.
6. Dark mummies produce vast numbers of sticky, resistant spores which remain infective for 3+ years.

Question 7

How to avoid chalkbrood 7

Answer 7

Avoid

1. Making up queen mating nucs in little boxes with too few bees;
2. Chilling brood as we inspect, esp on cold, wet windy days
3. Dividing colonies leaving too few bees to cover brood;
4. Spreading brood early in season
5. Over-stimulating brood rearing in spring -> too much brood, not enough HB
6. Transferring combs from infected colonies.
7. Damp apiary sites

Question 8

Chalk brood treatment 3

Answer 8

1. Move onto clean comb with shook swarm/bailey frame change.
2. Requeen - some strains may be more resistant than others
3. Minimise stress

Question 9

Impact of Chalkbrood on colony 3

Answer 9

1. Rarely fatal to colony
2. Can depress honey yield
3. Colonies produce fewer drones because they are on extremities

Question 10

How would a beekeeper recognise chalk brood?

Answer 10

• (Caused by fungus Ascosphera apis.)
• White, fluffy fully-grown larvae or pre-pupae with tiny yellow ‘heads’, seen when bees remove the cappings. Look like a white ‘plug’ filling the cell.
• Plug starts soft and fluffy but hardens to a solid lump known as a ‘chalk brood mummy’.
• Bees try to remove the mummies.Hard mummies on the floor of the hive or below the entrance again may be in large numbers. Can be white or mottled grey.
• Mummies differ from stone brood mummies as they are softer and crumble when handled.
• Pepper-pot appearance of the brood.

Question 11

How does this differ from Stone Brood?

Answer 11

• Stone brood also caused by a fungus (Aspergillus flavus or Aspergillus fumigatus).Very uncommon.
• Fungus works in same way as chalk brood but larvae die after the cell is capped.
• Become very hard turning yellow then green when spores form.

Question 12

What factors are known to increase the chances of the presence of chalk brood? (4)

Answer 12

• Very common in the Spring when colonies expanding fast resulting in there being too few bees to keep all the brood warm.
• Slight chilling does not kill the larvae but favours growth of fungus.
• Small weak colonies susceptible as not able to retain heat so well.
• Avoid cool, damp conditions and inadequate ventilation
• Beekeeper should avoid giving extra brood to colonies that cannot cover

Question 13

What action can a beekeeper take to reduce chalk brood in a hive? (3)

Answer 13

• Have young queens and strong healthy colonies going into winter.
• Have adequate ventilation and avoid placing hives in damp, chilly areas.
• Frames containing a lot of chalk brood should be destroyed and replaced with new foundation
• If problem continues, try re-queening but this is not always effective.
• Essential oils including cinnamon oil and thymol have been found to inhibit the growth of chalk brood fungus,

Question 14

Give the cause of sac brood.

Answer 14

Morator Aetulas

Sac brood virus

Question 15

List the signs of the disease (5)

Answer 15

Virus kills the larvae after the cell is sealed.

• Colour goes from yellowish to light brown.
• Bees remove the cell cappings to reveal a fluid filled bag or ‘sac’.
• As it dries it forms a dark brown flattened scale shaped like a gondola or Chinese slipper.
• In the early stages when the cappings are not fully removed, the cell contents may be sticky and fluid but not ropey thus ruling out AFB.
• Pre-pupa dies inside the cell.

Question 16

Briefly describe how sac brood develops in an individual bee. (7)

Answer 16

Sac brood gets into larvae when it is young, about 2 days old.

• Kills the larvae after it is sealed in the pre-pupal stage.
• The virus causes the fifth moult when the pre-pupa changes into a pupa to go wrong. The tough cuticle is not shed and the space fills up with ecdysial, or moulting, fluid.
• This is the fluid produced during the moulting process and it separates the outer cuticle from the living layer of cells, the epidermis, underneath.
• Instead of becoming a pupa, the pre-pupa become enclosed in a fluid-filled bag or sac.

Question 17

How would a beekeeper deal with sac brood?

Answer 17

• No specific treatment. The disease is often fleeting with few larvae infected and the bees clearing them overnight.
• Can re-queen with a queen from a different strain as some queens seem to pass on genes that make their larvae more susceptible to sac brood.

Question 18

What is sac brood

Answer 18

Common viral disease affecting brood which rarely causes measurable harm

Question 19

What does sacbrood look like on frame and how larvae die 7

Answer 19

1. Found in capped cells - chewed like AFB
2. Infected larva change from pearly white to pale yellow
3. Prevents pupa shedding 5th larval skin - fluids accumulate under skin to give it a sac-like appearance
4. Death just before pupation with larva on its back: chinese slippers
5. Adult bees eventually uncap them
6. The scales forms as dead larvae dry out but are easy to remove
7. Infection continues via cell cleaning and larval feeding

Question 20

What is the impact of sacbrood on colony 1

Answer 20

Can shorten adult lives: stop feeding larvae, become foragers earlier and collect v little pollen

Question 21

How is brood infected in sacbrood virus 1

Answer 21

Nurse bees infect larvae when they feed larvae with infected brood food.

Question 22

How are nurse bees infected with sacbrood virus 2

Answer 22

1. Nurse bees get it from contaminated
   
   1. water,
   2. pollen
   3. nectar
   4. cleaning out larval remains
2. Virus viable for 4 weeks in larval remains, pollen or honey

Question 23

Treatment of sacbrood 2

Answer 23

1. Usually clears up on its own or Requeen
2. Combs can be reused as virus only viable for four weeks