Spring cleaning of varroa

The most important time for monitoring the varroa levelis in spring. (Other times can also be important!)

Last year I realized that the varroa level can differ quite a lot for the same colony just a week later you measured the first time – depending on when you did it. Why so? The explanation is that the bees are very active cleaning the colony from mites during a period in spring. If your bees have the ability to do that cleaning.

Last year

Last year I saw that if you want kind of a “true” varroa level for judging if the colony might need some help against varroa, the time of measuring is crucial. You use the threshold 3% varroa level for deciding if the colony needs treatment. The correct time last year was when the apple trees had flower buds just ready to emerge, the first flower buds were opening up a little. Of course, how much the sun could reach the trees, which sort of apple tree, etc. can influence.

When apple flower buds are starting to open up is a good time to measure the varroa level for getting the “true” figure in spring.

Last year I started monitoring the varroa level first week in May. Some colonies had a little more mites than I expected, especially for a sister group that had had lower varroa levels the year before and which showed no virus bees (DWV-bees). I decided to make another test a week later for those sisters, in the middle of May. To my surprise the varroa level then was much lower, in just a week. I saw that apple flower buds were just starting to open up.

Maybe it didn’t take just a week. The bees could well have been working on their spring cleaning for a longer time, but it didn’t give a good result until the apple buds were starting to open up.

This year

This year I started to measure the varroa level in the middle of May. But apple buds had not developed as far as last year. It had been the coldest April for 18 years. And May had been wet and chilly. Some colonies had more mites than I had expected, a few a lot more, even 8 %. But no crippled winged bees (DWV). I made some monitoring a week later, for example those 8 % colonies. And now this year in the beginning of the last week in May, the apple flower buds were just starting to open up. Season was at least one week later than last year. In those 8 % colonies varroa level were now down to 3 %! Astounding!

Also bees that had 3 % varroa level in the early test had lowered their varroa level a week later, to 2 %, etc.

The apple flower buds

If your bees have the power to clean out mites, they may have a special time doing that in spring. Some time before the apple flower buds are starting to open up.

You can check if your bees have this trait by testing the varroa level when appletrees are starting to showtheir leaves and tiny flower buds. And do it again a week later or more when apple flower buds are starting to open up. If the bees have lowered their varroa levels, bee happy!

If no apple trees grow in you area you will find other trees to follow! Read more about guidelines for getting varroa resistant bees here!

The hard board

The hard board 0.5 x0.5 meter in front of the colony can show what’s going on in the colony also in spring. I saw a colony “aborting” worker bees just before emerging. With no wings. I found some too early “hatched” bees on the hard board, not moving. They were too young. With the second varroa test that colony had lowered their varroa level from 4 to well under 3 %. That’s a sign of something going on in the colony. More things are most probablygoing on to be able toexplain the lowering of the varroa level.

Bees fight the mite in different ways. Getting rid of bees in cells with mites and getting rid of bees infected with pathogens like viruses are important ways of getting rid of mites.

In front of another colony where the varroa level first was well higher than 3 %, I saw “aborted” drones almost ready to emerge by themselves, as well as dragged out white drone pupae. No worker pupae here.

Some colonies that had 0% varroa level, the hard board was empty of everything, dead bees and anything else. So a hard board is quite useful in judging the status of the colony.

Remember the time of the apple flower buds!

Right time for monitoring varroa in spring