Henrik Hansen

American foulbrood: a review of its biology, diagnosis and control

American foulbrood (AFB) is a severe bacterial brood disease of honey bees. AFB is lethal to bee colonies if treatment is not carried out. The disease is distributed worldwide and can cause substantial economic losses. Foulbrood was first described in 1769 and although AFB has been in focus for decades it has recently become an increasing problem.

Progress of Paenibacillus larvae larvae infection in individually inoculated honey bee larvae reared singly in vitro, in micro colonies, or in full-size colonies

SUMMARY The progress of infection of American foul-brood (AFB), Paenibacillus larvae larvae, in honey bee (Apis mellifera) larvae, prepupae, and pupae were studied in in vitro rearings, micro colonies and full-size colonies. P. l. larvae spores in various known numbers (3–1384 spores per larva) were inoculated at a larval age of 24–28 h. The in vitro study suggested that survival time decreased with increasing spore inoculation dose. No larvae inoculated with three spores died before day 6, but 30% of the larvae inoculated with 1384 spores had died at day 4, 36 h before the time of capping (in a bee colony). On day 4, approximately 480 000 bacterial colonies were cultured per larvae inoculated with 1384 spores at a larval age of 24 h. Viable counts of P. l. larvae per larvae from inoculation and four weeks onwards fitted (R2 = 0.917) a standard model for bacterial growth: lny = b ln (1+ exp (a—rt)), where y is predicted viable count, r is growth rate, t is larval age in hours, and b and a are constants. Bacterial growth rate in the four weeks infection period was estimated to be r = 0.179±0.030 h−1. In the queen-less micro colonies and full-size colonies the first signs of AFB were not visible to human eyes until day 4. By day 3 nurse bees removed 40% and 50 % of the inoculated larvae, respectively, indicating that they are able to detect infected larvae before disease symptoms are visible. An early removal behaviour probably is a very important trait to focus on when breeding for resistance against AFB. The removal behaviour of nurse bees in micro colonies was well correlated with removal in full—size colonies. We conclude that, the micro colonies may serve as a labour and time saving model for full—size colonies when testing the removal behaviour of selected bee lines.

Bats and bees are pollinating Parkia biglobosa in The Gambia

A pollination experiment was conducted with Parkia biglobosa (Fabaceae) in The Gambia. P. biglobosa is integrated in the farming systems and produces fruit pulp and seeds used in cooking. The species is bat-pollinated, and in areas with few bats the main pollinators are assumed to be honey bees. A higher rate of effective pollination will in many instances increase fruit production, and the aim of this study was to investigate pollination efficiency of different pollinators. Access of flower visiting animals to flowers was controlled by nets with differently sized mesh, using five trees as replicates. The pollinators’ identity, efficiency, and relative effect were determined. Bats, honey bees, and stingless bees were able to pollinate the species. Bat-visited capitula produced more pods, but not significantly more than honey bees. Honey bees were more efficient than stingless bees, resulting in significantly less aborted seeds. The treatment which excluded all flower visitors developed no mature pods, indicating that P. biglobosa was not autonomous autogamous, apomictic, or parthenocarpic, while the treatment with confined honey bees showed that geitonogamy is possible. Sugar content of fruit pulp was analysed and a positive correlation between number of seeds per pod and the sugar content was found. Improved pollination success may thus result in sweeter fruits. We conclude it is important to strive against a pollinator-friendly environment in order to attract bats and bees. Furthermore, we suggest beekeeping in the vicinity of P. biglobosa as a way to increase yield.