VARROA
MANAGEMENT

The Varroa destructor is a parasitic mite that significantly affects honeybee colonies by feeding on bee larvae and adults. This can weaken the bees and make them more susceptible to diseases, potentially leading to colony collapse if not managed effectively.

When to Treat for Varroa:
Varroa treatment in the UK typically follows a seasonal schedule:

Late Winter/Early Spring (February to March): This is an essential time for monitoring mite levels as the colony is starting to expand. A treatment at this time can help reduce the mite load before the population increases.

Late Summer (July to August): After the honey harvest, it's crucial to treat the bees to reduce mite levels before the bees start raising winter brood. High mite levels in late summer can severely weaken the colony going into winter.

Autumn (September to October): A follow-up treatment may be necessary to ensure that mite levels are sufficiently low to prevent damage to the winter bees.

Chemicals and Treatments
Several chemical and non-chemical treatments are available for managing Varroa mites. It’s important to rotate treatments to prevent mite resistance.

Chemical Treatments

​

• Apivar (Amitraz): A widely used miticide that is very effective in killing mites. It is typically used in strips placed inside the hive for several weeks.

• Thymol-based products (e.g., Apiguard): These are natural thymol-based treatments that are effective when temperatures are moderate.

• Oxalic Acid: Used as a trickle or vaporization treatment, often during brood-less periods in winter, as it is most effective when little to no brood is present.

• Formic Acid (e.g., MAQS): A natural treatment that can be used during the brood cycle but must be applied carefully as it is temperature-dependent.

​

Non-Chemical Methods

​

• Drone Brood Removal: Varroa mites prefer drone brood, so removing capped drone brood can help reduce mite levels.

• Screened Bottom Boards: These allow mites to fall out of the hive and reduce re-infestation.

• Powdered Sugar Dusting: This causes mites to fall off bees, though it is generally less effective as a standalone treatment.

 

Honey Supers and Treatment
During Varroa treatments, it’s critical to consider the presence of honey supers.

Chemical Treatments and Honey Supers: Most chemical treatments should not be used while honey supers are on the hive. This is to prevent contamination of the honey with residues from the treatment chemicals.

When to Remove Honey Supers: Honey supers should be removed before applying most Varroa treatments. After the treatment period is over, and any residual treatment has cleared, the supers can be replaced. It’s advisable to wait the recommended period specified by the product before replacing the supers.

Monitoring and Reassessing
It is essential to monitor mite levels using methods like the sugar roll or alcohol wash before and after treatment to assess effectiveness. Continual monitoring helps in deciding if further treatments are necessary and ensures the colony’s health throughout the year.

 

1. Sugar Roll (Powdered Sugar Shake)
The sugar roll is a widely used method that is non-lethal to bees and provides a reliable estimate of the mite infestation level.
 

How It Works

Sample Collection: Collect approximately 300 bees (about half a cup) from the brood nest into a jar with a mesh lid.
Dusting with Powdered Sugar: Add a few tablespoons of powdered sugar into the jar, secure the lid, and gently roll the jar to coat the bees with sugar.
Mite Dislodging: Shake the jar over a white surface (such as a piece of paper) to collect the mites that fall off the bees. The sugar causes the mites to lose their grip on the bees, falling through the mesh lid.
Counting Mites: Count the number of mites on the paper and calculate the infestation level. Typically, more than 3 mites per 100 bees indicates a high infestation.
 

Advantages
Provides a quick estimate of mite levels and this can be repeated multiple times in a season and is non-lethal to the bees.

 

2. Alcohol Wash
The alcohol wash is another accurate method for assessing mite levels, but it is lethal to the bees sampled.
 

How It Works

Sample Collection: Collect around 300 bees from the brood area, as with the sugar roll.
Alcohol Solution: Place the bees in a jar with a screened lid and fill it with rubbing alcohol, windshield washer fluid, or soapy water.
Shaking and Mite Counting: Shake the jar vigorously for about 2 minutes. The mites will dislodge from the bees and fall through the screen. Pour the contents onto a white surface or sieve, and count the mites.
Calculation: The number of mites divided by the number of bees gives you the infestation percentage. More than 3 mites per 100 bees indicates a need for treatment.
 

Advantages
Provides a clear indication of the infestation level.
 

Disadvantages
Lethal to the sampled bees.

3. Drone Brood Culling and Inspection
Varroa mites preferentially infest drone brood because of the longer development time, making this a good method for monitoring.

How It Works

Drone Frame Installation: Place a frame specifically for drone comb in the hive. Once the comb is capped, remove it.
Uncapping and Inspection: Uncap the drone brood using an uncapping fork or knife, and inspect the pupae for mites.
Counting Mites: Note the number of mites present in the drone cells.

 

Advantages
Can be integrated into regular Varroa control by removing infested drone brood.
Does not require killing worker bees.

Disadvantages
Labour-intensive.
Only provides an estimate if the entire frame is uncapped.

4. Sticky Boards
Sticky boards are used to monitor natural mite fall and can give an ongoing picture of mite levels without disturbing the bees.

How It Works

Installation: Place a sticky board (a white board coated with a sticky substance or covered with oil) under a screened bottom board.
Mite Fall Collection: Leave the board in place for 3 days, then remove and count the mites that have fallen onto the board.
Counting and Analysis: The number of mites per day can be used to estimate the mite population in the hive.

 

Advantages
Non-intrusive.
Provides a long-term view of mite levels.
Can be left in place to provide ongoing monitoring.

Disadvantages
May underestimate mite levels because it only measures natural mite fall.
Requires careful counting, which can be time-consuming.

5. Visual Inspection
While less quantitative, visual inspections of adult bees and brood can provide early warning signs of a Varroa problem.

How It Works

Inspect Adult Bees: Look for mites on adult bees, particularly on the thorax or between the body segments.
Brood Inspection: Open capped brood cells (especially drone brood) to inspect for mites on developing bees.

Advantages
Can be done quickly during regular hive inspections.
No additional equipment required.

Disadvantages
Less accurate than other methods.
By the time mites are visible, infestation may be severe.

Conclusion
Effective Varroa management is crucial for the survival and productivity of honeybee colonies. By treating at the appropriate times and using the correct methods, you can control mite populations and ensure the health of your hives.