Varroa Mite Reinfestation Prevention: Robbing Screens, Drone Comb Removal, and Apiary Placement

Treating a colony and then watching its mite levels climb rapidly back to dangerous levels is a common and frustrating experience. Reinfestation is real and common, particularly in areas with high beekeeper density or untreated feral colonies. Understanding how mites spread and taking practical steps to reduce reinfestation pressure extends the benefit of treatment and reduces how often you need to treat.

How Reinfestation Occurs

Varroa spreads between colonies through three primary mechanisms: drifting bees (bees that enter the wrong hive accidentally, especially common in apiaries where hives are arranged in lines with similar entrances), robbing (strong colonies rob honey from weak colonies, and bees that robbed from a mite-infested hive return with hitchhiking mites), and swarms that establish in proximity to existing colonies. A successfully treated colony in an area with heavily infested neighbors can go from 0.5 percent back to 2 to 3 percent within 4 to 6 weeks during a robbing period.

Robbing Screens

Robbing screens add a barrier to the entrance that forces bees to navigate an indirect path to enter, giving guard bees more time to inspect and reject non-colony bees. They do not eliminate robbing but significantly reduce it during flows when robbing pressure is highest. Install robbing screens when robbing behavior is observed (erratic flying, fighting at the entrance, bees clustering under the bottom board) or when flow ends abruptly. Keep screened bottom boards clean to maintain good airflow.

Drone Comb Removal

Varroa preferentially reproduces in drone cells (by 8 to 10 times over worker cells in some studies). Drone comb trapping involves placing a frame of drone foundation or comb in the brood nest, allowing it to be filled with drone brood, and removing it when capped. This removes a significant portion of the mite's preferred reproductive substrate from the colony. Freeze the frame for 48 hours before returning it to kill any remaining mites and larvae, then thaw and re-insert for bees to clean and refill. This method reduces mite population growth rate but does not replace treatment.

Apiary Placement and Neighbor Coordination

Site apiaries away from other untreated beekeepers when possible. In urban and suburban areas this is difficult, but in rural settings, 2 to 3 miles of separation from known untreated colonies substantially reduces mite immigration pressure. Coordinate treatment timing with other beekeepers in your area so that mite-burdened colonies are not spreading infested bees to recently treated neighbors during August robbing season.