Mites and DWV in low and highly infested colonies.

(A) Number of mites per 1,000 bees. (B) Seasonal prevalence of Deformed wing virus (DWV) in low and highly infested colonies. (C) Number of DWV genome copies in infected honeybees, collected in September and October from low and highly infested colonies. The error bars indicate the standard deviation; mean values significantly different are denoted with asterisks (*P≤0.05; **P≤0.01). Mite population steadily increased along the season in untreated colonies; DWV prevalence approached 100% at the end of the season both in low and highly infested colonies, but the number of genome copies was much higher in highly infested colonies.