Effect of shaking honey bee colonies affected by American foulbrood on Paenibacillus larvae larvae spore loads

SUMMARY

Honey bee (Apis mellifera) colonies exhibiting clinical symptoms of American foulbrood (AFB, causative agent Paenibacillus larvae larvae) were divided into 2 groups that received different shaking treatments: (1), shaking adult bees into a new hive; and (2), shaking adult bees in front of the entrance to a new hive. Honey bee and honey samples were taken before shaking and 1, 22, 44 and 66 days after shaking. Microbiological cultures were made from honey and honey bee samples to determine P. I. larvae development. The average number of P I. larvae cfu/g honey before shaking was 89.86 ± 17.93 (x ± s.e.) and more than 500 cfu/bee for honey bee samples. Honey bee samples had more colony-forming units before shaking but differences were not statistically significant after shaking. An important reduction in the number of colony-forming units in honey bee and honey samples was detected after shaking by both methods and no significant difference was detected between them. Honey and honey bee samples were positive for the presence of P. I. larvae in every sampling but no AFB clinical symptoms were detected in the honey bee colonies after 5 months. These results allow us to conclude that both shaking methods reduce spore loads in new colonies without using chemicals and, using them with other management procedures would allow development of an integrated AFB control method.

Keywords:

• American foulbrood
• Paenibacillus larvae larvae
• honey bees
• Apis mellifera
• shaking
• spores
• diagnosis
• control methods
• Argentina