3.12-3.15 - Varroa

Question 1

Impact of varroa on colony 5

Answer 1

1. Spring collapse - Early deaths of older bees before there are enough younger bees to take on their roles > Colony breakdown
2. You get viral symptoms in bees and brood
3. Can trigger previously harmless viruses
4. Bees get unrelated diseases due to weakened state of colony and supressed bee immune response.
5. Bees may abscond, invading other colonies (with phoretic mites)

Question 2

Describe signs of varroosis 5+3

Answer 2

1. Maybe none for a long time
2. Abnormal brood development - eg DWV
3. Dramatic population losses
4. Underweight bees on emergence
5. Parasitic mite syndrome/varoosis can look similar to AFB
   
   1. Sunken and chewed cappings
   2. White/yellow larvae slumped in the bottom or side of the cell.
6. Dries to removable scale

Question 3

Impact of varroa on bees 5

Answer 3

1. Can be present with no effects until levels build up
2. Shortens life leading to major population losses
3. Makes bees more susceptible to other diseases
   
   1. Mites activate viruses already present
   2. Mites may carry and transmit viruses
4. Only non-parasitised autumn-born bees are likely to survive till spring.
5. Workers with several mites likely to suffer from PMS and die.

Question 4

Signs of parasitic mite syndrome 7

Answer 4

1. Chewed/sunken cappings similar to AFB
2. Pepperpot brood pattern
3. Dead untended brood
4. Larva slumped on lower wall with varroa feeding on them
5. Larvae also spiral up the cell wall or coil in a c-shape at the opening
6. Larvae are white or yellow but not coffee with milk
7. Dry to a scale. Unlike AFB, scale can easily be removed. No matchstick rope

Question 5

Describe the varroa life cycle 12

Answer 5

1. Female varroa rides on honey bees in ecto-parasitic stage, feeding on fat body between ventral abdominal segments (for between 5-11 days)
2. Brood pheromones indicate when the larva is ready to be sealed, gravid females enter brood cell and hide in the brood food, breathing through two breathing tubes (peritremes)
3. 4-hours after sealing, she emerges from brood food, pierces larval cuticle and feeds on its fat body, gaining weight rapidly
4. After 60-70 hours she lays one unfertilised egg, a male, on the side of the cell.
5. Thereafter, every 30 or so hours she lays a fertilised female egg on the side of the cell – a total of 4-5 eggs
6. The eggs develop fast and hatch, and pass through two juvenile stages (protonymph and deutonymph) before becoming adults
7. Juvenile mandibles are soft and cannot break into larva so they feed at hole created by mother
8. Egg to adult male 5-6 days and he mates with his mature sisters; Egg to adult female is 6-7 days.
9. Male and immature females die in the cell.
10. Bee emerges with mother and newly mated female mites
11. Female can reproduce up to 4 times,
12. Live 2-3 months in summer, up to 5 months (ectoparasytically/ phoretically) in winter.

Question 6

Suggest why the population of Varroa increases continuously in a honeybee colony? 3

Answer 6

1. Each female varroa can have 3-4 brood cycles
2. producing an average of 1-45-1.72 female mites per worker cell and 2-3 per drone cell
3. Apis mellifera cannot reduce the population without outside intervention

Question 7

Suggest why Varroosis has spread so quickly throughout the UK 6

Answer 7

1. A mellifera has no natural defence against varroa
2. Varroa has built up resistance to certain treatments
3. Can survive the winter in the phoretic stage on hosts
4. Beekeeper can spread it - uniting and migrating bees, sharing brood comb etc
5. Bees tx the mite when they drift, rob, swarm, and on drones
6. Colony collapse leads to mite invasion as bees seek new homes

Question 8

Describe a varroa 6

Answer 8

1. 1.6mm wide x 1.1mm long shaped like a crab
2. males smaller and live out lives in brood cells
3. flattened body
4. reddish brown
5. 8 legs
6. Males smaller and never leave cells after mating with sisters.

Question 9

List three ways to detect varroa

Answer 9

1. Use OMF
2. Uncap drone cells.
3. Sugar roll

Question 10

Describe use of OMF to detect varroa 3

Answer 10

1. Monitor mite falls over a week and get a per-day average
2. This method is very sensitive and capable of detecting very few mites, does not disturb the colony.
3. It does encourage wax moths, takes several days and requires extra equipment.

Question 11

Describe drone uncapping to detect varroa 7

Answer 11

1. Drone pheromone acts as kairomone attracting female mites:
2. 100 uncapped cells with uncapping fork at pink eye stage by running the fork through the tops of the comb and lifting out the drones in a single action.
3. Varroa can easily be seen against the pale bodies of the drones.
4. Repeat for at least 100 drones.
5. If there are more than 5-10% of drone pupae are affected, the infestation is serious and colony collapse may occur before the end of the season.
6. Results are approximate and you may not detect a very light infestation.
7. The methods is quick and easy and can be done on routine inspections, giving an instant measure of infestation levels.

Question 12

Describe sugar roll to detect varroa 4

Answer 12

1. Take 300 bees from brood nest (to represent the colony) with jar and mesh lid and roll in handful of icing sugar for 2 mins
2. Set jar aside in shade for 2 mins and then shake sugar (and mites) out through mesh into shallow dish or water over a white surface.
3. Repeat rolling and shaking twice more then release bees at front of hive to return
4. 5 mites = 500 phoretics in colony = 1000 in total

Question 13

How often should you monitor for varroa and when

Answer 13

1. At least 4x season
2. Early spring
3. After spring honey flow
4. Honey harvesting time
5. Late autumn

Question 14

How often to monitor for varroa

Answer 14

1. At least 4x season
2. Early spring
3. After spring honey flow
4. Honey harvesting time
5. Late autumn

Question 15

Why monitor for varroa

Answer 15

1. It’s not possible to eradicate V destructor – it is now endemic
2. so monitoring allows the beekeeper to keep track of developments,
3. to check what treatments have worked and how well,
4. be aware the mite recovery period,
5. to know when to retreat and to know if an invasion has taken place.

Question 16

Varoa detection methods

Answer 16

1. Use OMF
   
   1. monitor mite falls over a week and get a per-day average
   2. This method is very sensitive and capable of detecting very few mites, does not disturb the colony.
   3. It does encourage wax moths, takes several days and requires extra equipment.
2. Uncap drone cells.
   
   1. Drone pher acts as kairomone attracting female mites:
   2. 100 uncapped cells with uncapping fork at pink eye stage by running the fork through the tops of the comb and lifting out the drones in a single action.
   3. Varroa can easily be seen against the pale bodies of the drones.
   4. Repeat for at least 100 drones.
   5. If there are more than 5-10% of drone pupae are affected, the infestation is serious and colony collapse may occur before the end of the season.
   6. Results are approximate and you may not detect a very light infestation.
   7. The methods is quick and easy and can be done on routine inspections, giving an instant measure of infestation levels.
3. Sugar roll.
   
   1. Take 300 bees from brood nest (to represent the colony) with jar and mesh lid and roll in handful of icing sugar for 2 mins
   2. Set jar aside in shade for 2 mins and then shake sugar (and mites) out through mesh into shalow dish or water over a white surface.
   3. Repeat rolling and shaking twice more then release bees at front of hive to return
   4. 5 mites = 500 phoretics in colony = 1000 in total

Question 17

When to take action with varroa 6

Answer 17

1. Winter/spring 0.5 mites per day
2. May 6 mites
3. June 16 mites
4. August 33 mites
5. September 20 mites
6. Most accurate with no brood/good sized nest

Question 18

How can you find out about approved veterinary medications and how should you use them? 3

Answer 18

1. The NBU produces a booklet on varroa which lists the approved medications - but it not up to date with latest approved medications.
2. The Veterinary Medicines Directorate (online) lists ALL the approved medications.
3. Only used approved medicines and follow the manufacturer’s instructions precisely.

Question 19

Authorised treatments for varroa Amitraz

Answer 19

1. Apivar, Apitraz
   
   1. Amitraz Plastic strips.
   2. Spring/summer.
   3. NO super withdrawal
   4. Contact/systemic.

Question 20

Authorised treatments for varroa: Apiguard

Answer 20

1. apigGUARD.
   
   1. Thymol gel in packs.
   2. Spring/later summer 4-6 weeks.
   3. Evap contact, ingestion: close vents,
   4. Dep on temp

Question 21

Authorised treatments for varroa Api Life Var

Answer 21

1. Api Life Var.
   
   1. Thymol eucalyptol, mentol and camphor, tablet.
   2. Autumn 3-4 weeks after harvest
   3. Evap: dep on temp

Question 22

Authorised treatments for varroa MAQS

Answer 22

1. MAQS
   
   1. formic acid Pads
   2. Even in honey flow. spring/summer/autumn. Not above 30˚C, Down to 10˚C
   3. 7 days
   4. Evaporation.
   5. Can kill mites in sealed cells

Question 23

Authorised treatments for varroa Pyrethroids

Answer 23

1. Bayvarol, Apistan:
   
   1. Pyrethroid strips
   2. spring/autumn.
   3. Check for resistence.
   4. Contact

Question 24

Authorised treatments for varroa Thymovar

Answer 24

1. Thymovar
   
   1. Thymol Strips
   2. Late summer 2 treatments over 3-4 weeks.
   3. Evap: 20-25˚C not above 30˚C

Question 25

Authorised treatments for varroa winter

Answer 25

1. Api-Bioxal, OxuVar, VarroMed, OxyBee
   
   1. oxalic acid solution.
   2. Winter in phoretic stage.
   3. Evap/contact.

Question 26

Discuss the impact of re-infestation of Varroa on the management 6

Answer 26

1. A mellifera has no natural defence against varroa
2. Varroa has built up resistance to certain treatments
3. Can survive the winter in the phoretic stage on hosts
4. Bees tx the mite when they drift, rob, swarm, and drones
5. Colony collapse leads to mite invasion as bees seek new homes.
6. Beekeeper can spread it - uniting and migrating bees, sharing brood comb etc.

Question 27

Suggest why the population of Varroa increases continuously in a honeybee colony? 2

Answer 27

1. Each female varroa can have 3-4 brood cycles
2. producing an average of 1.5 mites per worker cell and 2-3 per drone cell
3. 100 mites produce 1000 miles in worker cells in 7 seven weeks
4. 100 mites produce 5700 mites in drone cells in 7 seven weeks
5. A mellifera cannot reduce this population without outside invervention.

Question 28

Why might a colony be strong at honey harvest and then collapse from varoosis? 6

Answer 28

1. Number of bees declines nutuarally as autumn approaches, as does brood
2. Mite numbers likely to be at their greatest and infect a greater proportion of the brood
3. 1x mite results in very weak bee unable to carry out normal duties.
4. Several mites lead to PMS
5. Weakened colonies can be robbed so they end up short of food.
6. Only 10% of the mite population will die when brood rearing stops, but bees are not broodless long enough for this to have an impact alone

Question 29

Discuss the impact of reinfestation on the timing of varroa control

Answer 29

1. No single ideal time for treatment
2. Usually late summer after harvest as prep for winter to protect last brood cycles that produce the young bees that are needed for overwintering.
3. Delays may lead to winter bees carrying higher pathogenload > shorter life, dwindling, death of colonies even if VD controlled.
4. Also common to treat in spring when monitoring suggests they bees ahve emerge from winter with a mite pop that will pose a serious risk before leate summer treatment.
5. Some treatments reqquire broodlessness, some are temp dependent. Most require honey removal.

Question 30

Explain how to monitor varroa levels in a colony using the natural mite drop and the drone uncapping methods.

Give the advantages and disadvantages of each method. 20

Answer 30

Mite Drop
• Requires open mesh floor with Varroa sampling drawer/tray underneath.
• Tray needs to be clean at start of sampling period (and cleaned at intervals if kept in place for long periods.)
• At least four times a year (early Spring, after the Spring honey flow, during the honey harvest and late autumn), check the floor debris and count the number of Varroa mites. Convert this to a daily ‘mite drop’ by dividing the number of mites by the number of days the tray has been in.
• If there is a lot of debris the mites can be difficult to see. Mix the debris with methylated spirits in a large container. Most dead mites will float to the surface, whereas wax and propolis particles sink.
• Research has shown that natural mite drop is related to the size of the Varroa population.
• Use the table on BeeBase to decide if you need to treat.
Pros:
• Capable of detecting very few mites.
• Good idea of infestation level
• Colony not disturbed
• Can be used at any time of the year
Cons:
• Needs additional equipment
• Monitoring takes several days
• Encourages wax moth if debris accumulates

Drone Brood Uncapping
• Choose an area of sealed brood at an advanced stage of development (pink-eyed) so less likely to disintegrate.
• Slide prongs of de-capping fork under the domed cappings, parallel to the surface and lift out
the drone pupae in a single scooping motion.
• Repeat until at least 100 pupae have been examined.
• Mites are easy to to spot against the pale drone bodies.
• Estimate proportion of pupae that have Varroa mites on them.
• If 5% to 10% infested then there is a serious infestation that needs attention.
Pros:
• Quick and easy to use.
• Can be done during routine colony inspections
• Gives instant indication of infestation level.
Cons:
• Unlikely to detect a very light infestation.
• Results are approximate.
• Drones not present all year round.

Question 31

Varroa Resistance to Treatment

Answer 31

Chemicals:

Apistan, Bayvarol and PolyVar yellow

by:

Using the same treatment on every occasion.
Not following the instructions - using incorrect dosage, leaving it on too long, using it more than necessary.

Question 32

List the bio-technical treatments to which Varroa cannot become resistant

Answer 32

Comb trapping, drone brood removal, artificial swarm, shook swarm and open mesh floor.
More recently queen trapping has been used.

Question 33

State the limitations of 4 approved Varroa treatments 4

Answer 33

• Open mesh floor - not sufficient if used alone
• Drone brood removal - Limited efficacy and drones are needed in colony
• Comb trapping - time consuming, requires good skills and needs to be used at the correct time inthe season.
• Artificial swarm - only suitable in the swarming season; take precautions to avoid absconding by placing queen excluder under the brood box.

Question 34

Give a detailed description of the life cycle of the varroa mite. Give approximate duration, in hours or days, for each stage.

Answer 34

Two phases:

• Ectoparasitic phase when the adult female mites are feeding/living on the adult honey bee.
• Reproduction phase when the adult female mites are inside the sealed brood cells.

Ectoparasitic phase

• Mites burrow under the gap between third and fourth sternite plate on the left hand side (Ramsey)
• After a week or when sated from feeding on the fat bodies of the adult bee, the adult female mites are triggered by a keromone emitted by the larva that it will shortly require capping. Ectoparasitic phase ends.

Reproduction phase

• Female mite enters the cell, preferably a drone cell, and submerges into the brood food. She extends two breathing tubes, peritremes, up to the surface.
• Four hours later, when the cell is sealed, she emerges and attaches herself to the larva setting up a feeding site.
• 60-70 hours after capping she lays her first egg which is always a male. She then lays 4 or 5 more eggs at regular 30 hour intervals depending on whether she is laying on a worker or drone larva.
• Development of the egg is through two juvenile stages (protonymph and deutonymph).
• Once the mites have completed the deutonymph stage they are sexually mature and able to mate.
• Male mites reach the adult form in 5-6 days and the females in 6-7 days. The nymphs share the feeding site with their mother as they are unable to pierce the skin on their own. They feed on the fat bodies of the pupa.
• The male mites mature some 20 hours before the first female. They wait for the first female to appear and mate. Further matings take place as each female matures. Having mated with their sisters the males do not leave the cell when they do and die.
• The newly mated female mites and the mother leave the cell on the emerging bee.
• While up to 5 female eggs may be laid, attrition is high with an average of 1.45 mating females emerging per cell.

Next Step

• The female mites then spend a week or more on an adult host before the cycle starts again. A female mite may have up to four breeding cycles in her lifetime.

Note

• More than one mature female may enter a cell before it is sealed. • The temperature should be an optimal 36 to 38℃. The humidity should be an optimal 70%; reproduction is impossible if humidity exceeds 80% (Honey Bee Vet Medicine).