Brood diseases Flashcards
Chalk brood, sac brood, chilled brood and bald brood (38 cards)
What is chilled brood?
Side effect of the inability to maintain the optimal hive temperature of 34.5c required to rear brood.
Where in the brood nest are you likely to see evidence of chilled brood
At the edges of the brood nest where bees will withdraw from when cold
Under what seasonal circumstances might you see chilled brood?
When there are insufficient numbers of bees to maintain the hive temperature cover the brood
During spring temperature fluctuations
What beekeeping actions might result in the colony developing chilled brood?
Spreading brood unwisely
Splitting with too few bees
Often occurs in splits away from the original parent site (foragers return leaving bees short)
What are the symptoms of chilled brood?
- Brood of all ages (inc eggs) turns yellow, grey, brown or shiny black
- Especially on periphery of brood nest
- Brood die in cells
What actions can you take to prevent chilled brood?
- Using dummy boards to reduce nest size in hive
- Keeping inspections short
- Only inspecting over 16 degrees
- Do not expose brood for any length of time to temperature below 14c (mild chilling at 30c can increase susceptibility to chalk brood)
- Limiting brood spreading especially early in the season
- Making spilts with plenty of emerging brood and young bees shaken in
- To retain workers will have to close hive and move bees 3 miles away
What are the three common causes of bald brood?
1) Wax moth (galleria mellonella and achroia grisella)
2) Poor spacing of frames
3) Rarely, can be a genetic fault with the Q
How do wax moth cause bald brood?
By tunnelling under the cappings and exposing the larvae
Why does poor frame spacing cause bald brood?
When beespace has not been maintained, bees uncap cells in order to give themselves space to work
What are the signs of bald brood in the hive?
- Cell opening circular and slightly raised, not ragged or nibbled
- Plump, healthy pupae with no signs of cannibalism
- Wax moth leave uncapped larvae in straight lines
Why would ragged, nibbled, unhealthy or partly cannibalised brood be of concern
It may signify disease or starvation
How could a beekeeper cause bald brood?
By leaving too little space between frames
How can you combat bald brood?
(3 things)
- Control wax moth by keeping strong, health colonies
- Maintaining proper bee space between frames
- Returning frames to the hive in the order that they were removed
What is the causative agent of sacbrood?
Virus
Who does sacbrood affect and when?
- Affects capped brood – removed from cells by house bees
- Adults – generally asymptomatic but can interfere with the secretion of brood food
When is sacbrood likely to occur?
- Often occurs in spring or early summer
- Can be seen in autumn concomitantly with varroosis
- Can also occur in times of food deficiency
- Often occurs concurrently with other brood disease
What age of larvae are most susceptible to the sacbrood virus?
Between 2 and 8 days old
How is the sacbrood virus transferred to the larvae?
By ingesting infected brood food from infected bees
Evidence it is vector borne by varroa (2014)
How can adult bees become infected with sacbrood?
-Removing sacbrood corpses from cells (liquid filled with virus particals)
-Ingesting infected pollen and honey (can be infectious for up to 1 month)
-Queen can pass virus via eggs (vertical transmission)
-Robbing
How could a beekeeper aid the transmission of sacbrood between colonies?
Transfer of frames
Use of infected equipment / tools between colonies
How does sacbrood affect the larvae?
- Virus causes the 5th moult to go wrong (pre-pupa to pupa)
- Outer cuticle not shed and fills with ecdysial (moulting) fluid
- Larvae dies
How does Sacbrood affect the adult bee?
- Shortened lifespan – but can remain outwardly asymptomatic
- Accelerated development into foragers
- Pollen aversion – affecting brood rearing and foraging (favours nectar instead)
- Stop feeding larvae and does not collect pollen
What happens to a sacbrood larva when it dies?
- Changes colour – yellow to brown spreading from the head down
- Thickened skin filled with granular, brownish, watery liquid
- Will gradually rot down into a scale – easy to remove
What are the signs in the hive of sacbrood?
- Pepperpot brood
- Punctured cappings
- Chinese slipper/gondola larvae
- Sacs fragile and odourless
- Infected larvae become sticky and dark – thread up to 1cm can be drawn
- Then become dry, flattened gondola like scales – darker, drier cephalic part
