Influence of worker age on the infestation of resistant and susceptible honey bees (Apis mellifera) with tracheal mites (Acarapis woodi)

In an earlier study, resistant and susceptible workers exposed to tracheal mites one, two, three or four days post-emergence showed a decline in infestation. I further investigated the combined effects of worker age and of strain on infestation with tracheal mites. In four separate tests, workers were aged to evenly distributed classes reaching maximum ages of 9, 24, 48 and 96 h. The following factors influenced infestation levels: (1) overall, infestation of workers from resistant colonies was significantly lower than for susceptible colonies (2) age produced parallel rates of decline in infestation in both resistant and susceptible workers in the first three tests and (3) in the test up to 96 h, the large infestation differences in the youngest workers became very similar in workers aged three or four days. The differences between strains were highest at the youngest ages in all tests, indicating that evaluations of potentially resistant colonies should use the youngest workers possibl