THE EFFECT OF DRIFTING HONEY-BEES ON THE SPREAD OF AMERICAN FOULBROODINFECTIONS

Twenty-five pairs of honey bee (Apis mellifera) colonies were establis hed with the hives in each pair touching and the entrances facing the same direction. One colony in each pair had a light American foulbrood (AFB) infection (<50 larvae with clinical symptoms) while the other ( control) was uninfected. The pairs remained together for 5-388 days (a verage 103 days). Any heavily infected colonies (<50 larvae with clini cal symptoms) were removed from the trial. Only 2 of the control colon ies developed AFB. In a separate trial with two pairs of colonies esta blished in the same way, an average of 5.72% of marked bees were in th e wrong hive after two days. Trials where 20 uninfected nucleus coloni es were fed 50 000, 500 000 or 5 million Bacillus larvae spores in sug ar syrup indicated that the control colonies were not particularly res istant to AFB; four of five colonies fed 5 million spores developed AF B. The results suggest that drifting of honey bees is not a particular ly important cause of the spread of AFB.