Use the percentage of mites from the sugar roll test to decide on treatment methods as part of integrated pest management.
Here are a few of many treatment options to decrease the varroa mite load. Some of them work better than others.
1. Delay treatment
Sometimes this is the best method, especially if mite loads are small.
2. Screened bottom board
A screened bottom board allows mites to fall off of bees and through a screen in the bottom board and out of the hive or onto a sticky board. This method is not very effective. It eliminates 10-20% of mites (leaving 80-90% of mites on bees). Having a screened bottom board can also chill brood in cool weather. It can be part of an integrated pest management program.
3. Drone brood removal
Drone brood removal is labor-intensive, but effective. To use this method, you will need a frame of drone comb for each hive. These are commercially available. We’ve used the solid plastic drone combs from Pierco.
Place the drone comb in the hive. When bees have drawn comb and there are sealed drone cells, remove the frame and freeze it, killing the drone brood and mites that have crawled into drone cells to reproduce.
The timing on this method is critical. Be sure to remove the comb after the drone cells are sealed but before they start to emerge. If you let the drones emerge, you are helping the mites reproduce.
Once the drone comb is removed, place it in the freezer for more than 36 hours to kill the mites and the drone brood. The 36 hours is also critical to kill all of the mites. After 36 hours, place combs back in the hive. Workers will remove the dead drone brood and refill the wax with more drone brood.
Repeat this method until mite load has decreased.
I just saw on Mann Lake’s website a Mite Zapper, which electrocutes a frame of drone brood using a similar method. We haven’t tried this, but thought it is interesting.
4. Powdered sugar
The idea with powdered sugar is to knock the mites off of adult bees in the hive. Sprinkle powdered sugar over bees and allow mites to fall off. This has limited effectiveness as half of mites are inside of the cells and powdered sugar will not affect them. Mites can also crawl back onto bees unless there is a screened bottom board.
5. Chemical treatments
First a few disclaimers.
- We think that bees should not be dependent on beekeepers for survival and that they can develop natural resistance to disease. Please use chemicals in the hive only as a last resort. Sometimes we let bees die rather than treat with chemicals. Try other methods first.
- Read and follow the label to keep chemicals out of hive products.
- Be careful handling these chemicals, as some are pretty poisonous
- We are NOT licensed pesticide applicators and legally cannot recommend pesticides for the hive. We also cannot recommend dosage levels. We do recommend following the pesticide label strictly.
Having said that, some options for treating varroa mites in honeybees include
- Thymol: ApiLife VAR or Apiguard
- Formic Acid, like in Mite Away Quick Strips
- Oxalic Acid, available at chemical supply stores
- Potassium salt of hop beta acids, like Hop Guard
- Fluvalinate, like in apistan
- There are probably newer chemical treatments not listed here.
IF (big if) we treat our bees for mites, we use oxalic acid vapor, as it is a chemical found in honey (in very small quantities). We might also look into formic acid for the same reason.
When researching which chemical to use, here are a few places to look.
1. A beekeeping trade journal, like the American Bee Journal or Bee Culture.