Response of in vitro reared honey bee larvae to various doses of Paenibacillus larvae larvae spores

Abstract

The relationship between the number of Paenibacillus larvae larvae spores fed individually to 24-28, 48-52 and 72-76 h old Apis mellifera ligustica larvae and the number of larvae dying from the P. l. larvae infection was investigated as well as the effect of sublethal infection with P. l. larvae on larval development time and adult weight. The larvae were laboratory reared, thus, excluding the influence of nurse bees. The results show that larvae 24-28 h old are most susceptible to infection with P. l. larvae with a clear dose-response relationship (LD50 = 8.49). Older larvae become more and more resistant to infection with P. l. larvae so that no significant dose-mortality relationship exists in the 48-52 and 72-76 h age groups. Furthermore, a significant negative correlation exists between the development time and emergence weight for the adult bees in both the non- inoculated group and the inoculated group. There was no difference in development time between non-inoculated larvae and those that survived the inoculation.