Blowtorch and Disinfection

A blowtorch (gas torch, propane torch) is a hand tool that produces a high-temperature flame from bottled gas; in beekeeping it is used to disinfect empty wooden hives, floors and metal tools by scorching. Scorching is the most common and practical method on wooden and metal surfaces, especially against very resistant disease agents. However, it only works on cleaned surfaces, cannot be used on plastic and foam hives, and does not replace official instructions in the case of notifiable diseases.

Why is hive disinfection necessary?

Hives, frames and tools left over from a colony that has died or become diseased can carry the spores of agents such as the foulbroods, nosema and chalkbrood for a long time. When a new colony is put into this equipment, or the tools go into other hives, the disease spreads.

The greatest danger is American foulbrood (caused by Paenibacillus larvae). Its spores can remain viable for decades; wiping with alcohol, leaving things in the sun or holding them briefly over a fire does not reliably kill them. That is why intense heat, meaning a flame, is the most widely used method on wooden and metal surfaces.

What is a blowtorch used on?

• Empty wooden hive bodies and supers: Inside surfaces, corners, frame runners.
• Floor and the inside of the lid: Places where faeces and debris build up.
• Metal tools: Hive tool, frame grips, metal queen excluder, entrance reducers, varroa floor mesh.
• Wooden frames: Sound frames with the combs cut out and cleaned (provided they come from a disease-free source).

What should a blowtorch not be used on?

• Foam (polystyrene) and plastic hives: They melt and deform. These are cleaned by chemical disinfection.
• Comb: Comb cannot be disinfected with a flame. Comb from a diseased hive is destroyed; old combs from healthy sources are melted down and used as wax.
• Plastic frames, plastic excluders and feeders: These are cleaned with hot soda water and a suitable disinfectant.
• Painted outside surfaces: Paint burns and gives off toxic fumes; scorching is done on inside surfaces only.

How do you disinfect a hive with a blowtorch? (Step by step)

1. Empty the hive: Remove the frames, the excluder and any plastic parts.
2. Mechanical cleaning: Scrape off propolis, wax, dead bees and faeces with a hive tool and scraper; clean corners and frame runners with a wire brush. A thick layer of propolis and wax keeps the flame from reaching the wood and catches fire, creating a fire risk.
3. A safe place: Work in an area away from dry grass and flammable materials, with no wind or sheltered from it; keep water or a fire extinguisher at hand.
4. Scorching: Move the flame slowly and evenly over the surface. Heat the wood until it turns light brown; do not burn it until it chars.
5. Corners and cracks: Corners, joints and frame runners are where spores collect; pay particular attention to them.
6. Cooling and checking: Leave the hive to cool; make sure there are no smouldering spots left. Do not leave the hive unattended.

Metal tools such as the hive tool are first scraped and washed in soda water, then held in the flame until the whole surface is thoroughly heated. Repeated heating can spoil the temper of hardened steel, so it is more practical to work with a spare tool.

What disinfection methods are used besides the blowtorch?

When using chemicals, follow the instructions on the product label; never mix different chemicals (especially bleach with acids or ammonia-based products). Disinfected equipment must not be given to bees until it has dried completely and the smell has gone.

Choosing and safely using a blowtorch

• Type: Beekeepers generally use small cartridge torches (for tools and small jobs) and cylinder torches with a hose and a wide burner head (for scorching hives). A wide-flame burner head speeds up scorching hives.
• Ignition: Models with a built-in igniter (automatic ignition) are easier to use with gloves on.
• Connections: Check the hose and connections before every use; do not use the torch if you smell gas.
• Cylinder: Do not leave the cylinder in the sun, in a vehicle or in a hot place; keep it upright.
• Personal protection: Bee suits and clothing containing nylon can catch fire easily; while scorching, wear cotton work clothes, leather gloves and safety goggles.
• When finished: Close the valve and let the burner head cool; keep an eye on scorched hives until they have cooled down.

Together with the smoker, the blowtorch is one of the main sources of fire in the apiary. In periods of high wildfire risk, follow the rules for working with open flames; if possible, do the scorching outside the apiary, on a concrete floor.

When should you disinfect?

• The hive of a colony that has died: If the cause of death is unknown, the hive should be scraped and scorched before a new colony is put in.
• Second-hand hives and equipment from another beekeeper: Always clean and disinfect them before use; do not use the old combs.
• Winter maintenance: Empty hives are scraped and scorched one after another out of season.
• Tool hygiene: After every hive when disease is suspected; in apiaries that look healthy, between groups of hives and between apiaries.

Common mistakes

• Scorching without scraping: The flame does not reach the surface and the propolis catches fire.
• Charring the wood: This shortens the life of the hive; the aim is a light brown colour.
• Scorching a foam hive: The material melts and the hive becomes unusable.
• Keeping diseased comb: Comb cannot be disinfected; with a notifiable disease it is destroyed as instructed.
• Thinking wiping with alcohol is enough: It is no guarantee against resistant spores.