How to test for hygienic behavior
This method is taken from “A sustainable approach to controlling honey bee diseases and varroa mites” Available http://www.sare.org/publications/factsheet/0305.htm May 20, 2008.
3 in. cylinder (PVC pipe)
10-15 oz liquid nitrogen (easily obtained from welding supplier)
Liquid nitrogen tank
Frame with more than 3 inches diameter sealed brood(Fewer than 30 unsealed brood in the circle)
Lay frame across empty super. Twist cylinder into sealed brood until it reaches midrib. Record the number of unsealed cells inside the cylinder. Pour 1.5 to 2.0 oz of the liquid nitrogen into the cylinder and wait for it to freeze the edges or evaporate. Then pour the remainder of the liquid nitrogen into the cylinder. Wait to remove the cylinder until it thaws (3-5 minutes). Put a thumbtack on the top of the frame to mark the frame and the location of the test on the frame. Some hygienic colonies clean and repair the comb so quickly that it is hard to locate the test when you return. Place the frame back in its box.
Remove the frame containing the frozen brood 48 hours later and record the number of sealed cells remaining within the circle.Bees are considered “hygienic” if they remove >95% of the brood on two consecutive tests. This trait is highly heritable and will help hives become resistant to diseases and mites.