4.3.2. Colony resistance
- It is important to test the viability of the AFB spores used to challenge the colony. A lack of clinical symptoms after challenge may be due to colony resistance (Spivak and Reuter, 2001) or the use of non-viable spores.
- An indirect way to test for colony resistance to AFB is to assay the colony for hygienic behaviour using the 24 h freeze-killed brood test, as outlined in the BEEBOOK paper on queen rearing and selection (Büchler et al., 2013). Colonies that remove >95 % of the freeze-killed brood within 24 hours, over two repeated tests, are likely to demonstrate resistance to AFB.
- It has not been established whether colonies that remove >95 % of pin-killed brood (another assay for hygienic behaviour) are also likely to be resistant to AFB. This needs to be tested.