Where can varroa mites be found in a bee colony? Key Infestation Hotspots Explained

Varroa mites primarily infest honey bee colonies by attaching to adult bees and hiding within brood cells, where they reproduce and feed on developing bee larvae. Up to 70% of a colony's varroa population can be concealed in these brood cells, making them a critical hotspot for mite activity. Effective management requires targeting both adult bees and brood cells, as mites move between these locations throughout their lifecycle. Treatments like oxalic acid can help control mites on adult bees, but a comprehensive strategy is needed to address mites in all colony areas.

Key Points Explained:

1. On Adult Bees

   • Varroa mites attach to the bodies of adult honey bees, particularly on the underside of the abdomen or between segments.
   • They feed on the hemolymph (bee blood), weakening the host and potentially transmitting viruses.
   • Mites may transfer between bees during contact, spreading infestation within the colony.

2. Inside Brood Cells

   • Female varroa mites enter brood cells just before they are capped, where they lay eggs on developing bee larvae.
   • Up to 70% of a colony’s mite population can be hidden in these cells, making them a major reservoir for infestation.
   • Mites reproduce inside the cells, with offspring emerging when the adult bee does, perpetuating the cycle.

3. Movement Between Life Stages

   • Mites alternate between phoretic (attached to adult bees) and reproductive (inside brood cells) phases.
   • They prefer drone brood cells due to their longer development time, which allows more mite offspring to mature.

4. Implications for Treatment

   • Oxalic acid and similar treatments target mites on adult bees but are less effective against mites in sealed brood cells.
   • Integrated pest management (IPM) strategies, including brood interruption or drone comb removal, are often necessary to reduce hidden mite populations.

5. Monitoring and Prevention

   • Regular monitoring (e.g., alcohol washes or sticky boards) helps detect mite levels on adult bees.
   • Brood inspections can reveal mite presence in cells, especially in drone brood.

Understanding these locations is essential for designing effective control measures, as mites exploit both adult bees and brood cells to sustain their population. Combining treatments with colony management practices offers the best chance of keeping infestations in check.

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