Why It is Important to Do a Mite Count After a Treatment

Today is the first day of the 2017 Mite-A-Thon sponsored by the Pollinator Partnership. This event seemed like a great idea, so I planned my next hive inspection date to coincide with Mite-A-Thon week. I was pretty sure my numbers would be pretty good. I test for mites during the first week of each month from March/April to September and kinda pride myself on staying on top of mites. In fact I may even feel pretty proud of myself for being so conscientious…  I’m participating in a virus study out of Montana this year, and my bee weights and virus loads were stellar in June, and pretty darn good in August.

For the last couple of years, my routine has followed the same pattern: treat with oxalic acid just before the Time of Increase at the winter solstice, test each month, treat with Apiguard in June or July, and August when necessary.  Before I started using oxalic acid in the winter, I’d usually have to treat with Mite Away Quick Strips (MAQs) at least once in the spring, but the oxalic acid seems to cut the mite population so much that it is not an issue until close to the Time of Decrease after the summer solstice. I prefer to use only these organic treatments and not deal with synthetic chemicals in the hive. This routine matches well with our area’s temperatures, which are often too hot in the summer to use MAQs.

Because I am a backyard beekeeper, I have the time to test each hive each month and treat as necessary. I keep track of all brood breaks, like swarms, supersedures, re-queening etc, and they definitely correspond to lower mite loads. If a hive is having a queen event, I don’t test that hive that month – I try to leave the hive alone to settle in.

I now test only from frames with open brood. I had been testing honey frames for safety – don’t want to get the queen. But I learned that the University of Minnesota Bee Labs recommends using an open brood frame where the mites are on the nurse bees waiting to jump into the cell just before it is capped. This is more reliable than testing from a non-brood frame and then adding a percentage to the mite count.

Using brood frames requires a careful inspection for the queen on the frame before the bees are collected. After I check for the queen on a frame with older larva ready to be capped,  I tap the frame briskly into a 12X8 inch plastic container and let the bees sit for a minute or two. The foragers fly off leaving the nurse bees who are more likely to harbor mites. Then I carefully inspect the bees in the container for the queen before I scoop up the test sample.

This year the pattern held true. I have 3 hives in my backyard apiary. My first mite tests were on March 10, 2017.  The hives tested at 0, 0, and 5 – two hives had 0 mites and the third had 5 mites per 300 bees or 1.6% (1.6 per 100 bees)- perfectly acceptable. Since mites tend to at least double each month I figured I might have to treat the third hive the next month – a bother. But, instead I did a preemptive swarm split when I saw swarm cells and the brood break took care of the issue.

By the July 3 mite count, the hives tested a 1, 1, and 3 mites per 300 bees. Sure enough, on August 5, they tested at a whopping 12, 13, and 5. YIKES. That was a huge increase – up to 4% infestation in only a month! This is typical of what I see though – the mite infestations just take off in July/August.

No Problem! I added Apiguard to each hive. I used a 1/2 dose – which I generally do unless it is a huge hive or a huge mite infestation. This was followed by another 1/2 dose in about 10 days. I made sure the screened bottom board was in place and the entrance reducers were on. The whole apiary smelled like Listerine.

Now for the September mite count and the Mite A Thon! I was shocked when I tested. Today the counts were 20, 30, and 6 per 300 bees!  Yes that’s right, 30!!! That is my record mite count – I’ve never seen it in the 30s. I grabbed my emergency Apivar and put 2 strips into each brood box for the two hives with the high counts. Apivar is synthetic, but this is an emergency. The bees haven’t been treated with it in several years.

Moral of the story – always test after treatment. The treatment does not always work. Perhaps I should not have fed syrup, perhaps the hive wasn’t closed enough, perhaps the bees were too efficient removing it and it did not spread. Perhaps 1/2 dose was a mistake. Perhaps they robbed out a mite infested hive. Perhaps my backyard bees are surrounded by mite bombs created by folks who don’t test for mites.

By contrast, my Talent apiary has tested below treatment levels all year. One hive had 6 mites at the August test, and I used Apiguard knocked it down to 1 for September.

The Mite A Thon survey form has information on the effects of mite levels. It is per 100 bees, so divide the number of mites you count in 300 bees (1/2 cup sample) by 3.

  • 0 – 3: Relatively low mite level, keep monitoring and managing (splitting, drone trapping, brood breaks, screened bottom boards) mite populations.
  • 4 – 5: Intervention (use of a miticide) will greatly increase chances of colony survival.
  • 6 – 10: Colony loss or damage likely. Intervention is critical to prevent colony loss from mite infestation.
  • 11+: Loss of colony likely. Intervention is essential to decrease the threat of horizontal transmission (spread) of mites to neighboring colonies.

So conventional wisdom has it that the hive with the 10% infestation (30/300 or 10/100) may be a goner. It looks great – packed with bees and resources, but we’ll see what happens. The 6.6 % infestation (20/300 or 6.6/100) at this time of year is awful too. If the Apivar works well, it might survive. I have hope based on the virus counts from July.

If I had not tested after the Apiguard treatment though, I’m sure the hives would be toast. Who knows what the count would have gotten up to!

Ellen Wright