Mite drop counts in Winter

[dragonfly]

Do mite drop counts remain consistent throughout Winter? In other words, when the weather is cold enough for them to cluster at night, then often warms enough during the daytime for them to fly, will mite drop be an accurate gauge of infestation? Does clustering tend to drop the number of mites dropped to the bottom of the hive?

[Michael Bush]

In my observation, mite drops seem to vary by the temperature. The warmer it is the more they drop. When it's cold and they are more tightly clustered there are less. But if you average it out it still gives you an idea what's happening.

Of course, DaveW has counted more mites than me. Perhaps he will weigh in. smile.gif

[George Fergusson]

>Do mite drop counts remain consistent throughout Winter?

I don't know exactly what you mean by "consistent". If you mean do they continue at a rate "consistent" with what you saw in the summer or fall, then likely no, they don't remain consistent. You are likely to see considerably LESS mites dropping in the winter than at other times of the year.

This is due to a number of factors but the biggest is because there is limited brood rearing going on during the winter. As a result, mite populations tend to be largely static, or might even drop some during the winter.

There are a lot of sources available that discuss mite drop counts, what they mean (in terms of total population), and thresholds for treatment. About the only thing they can agree on is that the drop (as a percentage of the total mite population) varies significantly during periods when there is brood rearing occuring and periods when there is no (or little brood) rearing going on, but that it remains fairly constant within those 2 periods. "Fairly constant" is open to interpretation. There is evidence that mite drop can also be affected by temperature and clustering, as Michael mentioned, and probably some other factors we don't know about.

Most mites that drop do so as a result of breeding. Mites can breed 2 to 3 times at most, then they die (and drop). Some number of mites fail to mature during breeding, and they drop. Some mites are removed by bees (grooming) or fall during emergence, and they drop. So if they're breeding, they're also dropping, and at a reasonably constant rate. If they're not breeding, they're still dropping, but at a much lower rate, though still at a reasonably constant one.

George-

[dragonfly]

Thanks for the info. I was mainly concerned that while bees are clustering, mites that fall would be hampered in the fall due to the tighter mass of bees, preventing normal mite falls based on the size of the colonies. I didn't want to happily delude myself into thinking my bees are okay when they are not smile.gif

[George Fergusson]

Clustering probably contributes to the lower drops in the winter for that reason, but the main reason is there's not much brood rearing going on, and most of the mites are phoretic (hanging and feeding on bees). Dead mites will eventually end up on the bottom, in spite of clustering. They're just not dying as fast in the winter. The phoretic phase of a mite's existance is relatively "safe". Mites can live on bees quite a while and don't typically just fall off unless they happen to be groomed off, and I don't know how much grooming is going on in a winter cluster.

George-

[Fusion_power]

Treatments for mites would be much more effective in winter when the colony is broodless. The treatment would have to be inserted into the cluster but could stay there only a few days.

Unfortunately, the cycle of the bees and mites is such that they peak in numbers in late fall. If you wait until winter to treat, you will have dead colonies.

The part I'm looking forward to is when most bees carry the VH genes. (VH = Varroa Hygenic)

Fusion

[George Fergusson]

>If you wait until winter to treat, you will have dead colonies.

If you wait until fall to treat you may have dead colonies anyways. I treated in late-summer and early fall and killed a lot of mites but I fully expect to lose a number of hives this winter due to weakened, shorter-lived bees. I should have nailed `em in early summer.

Treating in the winter is problematic. I'm personally of the opinion that bees should be left alone during the winter. They're also not totally broodless in the winter. Bees are typically broodless by mid to late fall and often at other times of the season, and broodless conditions can be created through caging the queen and/or timely and appropriate use of splits.

George-