Varroa: Brood interruption
Biotechnical control methods are increasingly being promoted in the fight against varroosis. Among these, techniques that induce significant interruptions in brood development are often discussed. However, such methods are still rarely used by beekeepers, except on an experimental basis. This article analyses the relevance of brood interruption and the different techniques derived from it.
Brood interruption as a tool against Varroa – principles and practical application
Brood interruption is a biotechnical method for controlling Varroa destructor that relies on temporarily stopping queen egg laying. This creates a broodless period during which all mites are present on adult bees, making them fully susceptible to treatment.
During the active season, up to 90% of Varroa mites are found inside brood cells, where they are protected from many treatments. Oxalic acid, for example, is only effective against phoretic mites. By inducing a brood break, the entire Varroa population becomes exposed, and mite reproduction is also reduced, as prolonged broodless periods increase the proportion of infertile female mites.
This approach mirrors natural processes. During swarming, egg laying stops for two to three weeks until a new queen is mated and resumes laying. This natural brood pause is considered an important factor contributing to the higher Varroa tolerance observed in swarms and feral colonies.
To achieve a completely broodless colony, the queen must be prevented from laying for about 22 days when only worker brood is present, and up to 24 days if drone brood is included. In practice, beekeepers often choose 24–28 days to ensure that no capped brood remains. The optimal timing is usually mid-July, after honey harvest, allowing colonies to rebuild their population before winter.
Treatment is carried out during the broodless phase, most commonly using oxalic acid applied by trickling, sublimation or spraying. Two closely spaced treatments are recommended, as mites rapidly re-enter newly laid brood once egg laying resumes.
Several techniques can induce brood interruption, including removal of capped brood, isolating the queen below the brood chamber, caging the queen, or using specialized devices such as the Scalvini cage. The Scalvini cage allows continuous egg laying but prevents bro
See also:
- Brood Break: Varroa Control
- Varroa Control: Summer Broodless Period
- Practical Guide: 1.6.1 Brood Break
- Integrated Varroa Control Throughout the Season
- Practical Guide: 1.3.2 Trickling Method
Source: Actu API 1-2017 71; http://www.cari.be