If you did take mite counts every couple weeks on hives, you probably would find a couple things....
1)Hives within the same yard will have drastic different counts.
2) You probably will have hives exhibit two type counts throughout the year.
a) Hive counts such as 1-5-3-8-4-6-7-5
b)Hive counts such as 2-7-4-9-15-31-28-42
Bjorn, if you're still reading I wanted to come back to this. What would you do if you saw a count pattern that looked more like this?
Last year, no issues, small increase in drop in Sept to a max of 12/day, then declining back to spring norms. No increasing trend during this year, bees by all appearances managing the mites, then BOOM.
Before the dearth this year, no abnormal DWV. I would see maybe 2 infected bees on inspection. I inspected much less frequently during the dearth this year because there was a LOT of robbing in the area, but did check the natural drop that yielded 0 mites in 72 hours. These bees sharply curtailed brooding during the dearth (a trait I'd love to breed for) so I figured a larger proportion of phoretic mites couldn't find a fresh host and the population had dropped off. Looked good for counts to be below 5 going into winter. The next inspection after the dearth revealed over a dozen DWV bees recently hatched, and the next mite drop was over 40.
I won't say I did drops every two weeks, of course, but this hive doesn't match either pattern you're describing.
What would you think had happened if you saw this pattern?
First, I should make it clear that I am not talking about mite drops as in using a sticky board. As others have pointed out, circumstances such as brood rearing ebb and flows, and other factors, all determine how many mites are falling or groomed off bees.
I would rather have a count based on sugar shake This accounts for most of the mites off a determined amount of bees, regardless of time of the season.
As for your question, that pattern is unique, but many factors could of played into it. Unreliable mite drops, timing of brood cycles, etc.
What was the date of the last two counts in reference to the other count numbers?
Certainly I would possibly take corrective action depending upon your IPM. I would also compare this count to other hives. Is this a single hive experiencing this? I would guess yes, since I don't put much weight behind the whole "leveling out" ideology, except for the slow steady transfer of mites that you will always have, then the dealing with any introduction of mites by the colonies ability to deal with it.
No doubt that the pattern of mite explosion is well documented. It can be somewhat level for three or four months and then between August 15 and October 15, the mites can multiply ten fold. I've seen that a thousand times when inspecting hives of others during this timeframe. That is a problem for the average beekeeper. Most beekeepers are excited going into the season, they inspect and do what they should for a period of time, then get tired of the bees and do far less inspections as the summer progresses. And this is the time when mites will come back and bite you.
I start winter prep after taking the honey off in late June. The fall brood cycle starts in mid August. And so it is very important that by August 15th, all issues are taken care of. requeening bad queens, dealing with mites, combining, etc. So this is the date I aim for to have my hives ready to go into the fall brood period. Because if i don't, mites and other issues will do their damage.
I hope this helps.