Varroa destructor is present in Brazilian apiaries, but its impact on Africanised colonies is measurably different from its impact on European honey bees. Africanised bees show stronger hygienic behaviour, which means they remove mite-infested pupae from capped cells at a higher rate. This does not make Varroa irrelevant in Brazilian apiaries, but it does mean that the monitoring thresholds and treatment protocols developed for European bees need to be applied with some adjustment.

Why Africanised colonies tolerate higher mite loads

Africanised honey bees (Apis mellifera scutellata hybrids) have a shorter capped brood period than European subspecies, which reduces the time Varroa mites spend in the protected environment of a capped cell. They also show higher rates of hygienic behaviour, detecting and removing mite-infested pupae before the mite completes its reproductive cycle. Studies conducted at UNESP Jaboticabal and at EMBRAPA Meio Ambiente have documented mite population growth rates in Africanised colonies that are significantly lower than those recorded in European colonies under the same conditions.

How to monitor mite levels accurately

The two most practical monitoring methods for small and medium apiaries are the alcohol wash and the sticky board count. The alcohol wash gives a more accurate mite load per 100 bees and is the method recommended by MAPA for official monitoring. The sticky board count is less precise but non-lethal and useful for tracking trends over time. For the sticky board, use a 24-hour count and divide by the number of frames of bees. A result of one or more mites per frame per day during the brood-rearing season warrants a second count in two weeks.

When to treat

The most effective treatment window is during a natural or induced broodless period, when all mites are on adult bees and accessible to contact or vapour treatments. In Southeast Brazil, natural broodless periods are uncommon in Africanised colonies, which tend to maintain brood year-round. An induced broodless period can be created by caging the queen for 24 days, which allows all capped brood to emerge before treatment. Oxalic acid vaporisation during this window achieves the highest efficacy.

Oxalic acid vaporisation: practical notes

Oxalic acid vaporisation is the most practical treatment option for Brazilian conditions. The 12V DC vaporiser pan is the most common equipment used in small and medium apiaries. Seal the hive entrance with a damp cloth before treatment and leave it sealed for ten minutes after the vaporiser is removed. Wear a respirator rated for acid vapours. The treatment is most effective at an ambient temperature above 15°C, which is rarely a limiting factor in most Brazilian regions.

Record keeping

Keep a record of every mite count and every treatment. A simple paper log with the date, the colony identifier, the mite count method, the result, and any action taken is sufficient. Over two or three seasons, the log will show you which colonies in your apiary consistently carry higher mite loads. These colonies are candidates for requeening with stock from a breeder who selects for hygienic behaviour.

Varroa management in Brazilian apiaries is manageable with a consistent monitoring routine and timely treatment. The oxalic acid vaporiser kit we stock includes a printed dosing guide. If you have questions about your mite counts, contact us and we will help you interpret them.