After a pleasant summer with virtually no varroa, mites erupted in my hives in October. Drones had been ejected before the outbreak. I live in coastal California and temps encourage forage activity through the fall, though the nectar in the brown hills doesn't really support any surplus. Dwarf Wing Virus really devastated some hives-- in fact the DWV seems more severe than the relatively mild mite counts.
Have others observed a sudden peak in mites and especially DWV in the period when hives have ejected their drones and converted to a winter brood pattern?
I know varroa follows an epidemic doubling pattern, but the summer counts didn't seem to build-- and were lower to non-existent in August-September than May. I'm supposing that winter brood may take a day or two longer to hatch and the extra time might push the mite and DWV infection, or the absence of drones might concentrate mites on the winter brood.
I drizzled 3.2% Oxalic in 50:50 syrup today. I was waiting for the "winter cluster" but on the coast that occurs only sporadically in December. Couldn't put off treatment and still expect to have survival.