The Varroa Arithmetic That Treatment-Free Claims Must Answer: Per-Cycle Growth, Threshold Crossing Dates, and the Removal Fraction Required to Hold a Colony Flat

This study is simulated, not measured. From stated assumptions, the mite population multiplies by 1.5729 per brood cycle outside the drone season and by 1.7181 per brood cycle during the drone season, so holding the load flat requires removing 36.4% of mites in an ordinary cycle and 41.8% in a drone-season cycle. A colony starting on 1 March with 50 mites crosses the 3% threshold on 2026-07-17 without a brood break and on 2026-08-12 with a summer brood break, ending the following February with 5243.2 mites without a break and 2471.1 mites with a break; the annual growth factor is 104.86 without intervention, 49.42 with one summer break, and 18.26 with drone brood removal and a break combined. Diligent drone brood removal delivers 26.7% removal of reproducing mites in drone-season cycles, after which the population still grows by 23.3% per such cycle, and it delivers nothing outside the drone season. Under these assumptions the claim that a healthy colony holds varroa in balance untreated is disproved: in every simulated case the load crosses both stated thresholds within the season and grows by a large factor over the year.