J.J.M. van der Steen

Control of varroa by combining trapping in honey bee worker brood with formic acid treatment of the capped brood outside the colony: putting knowledge on brood cell invasion into practice

SUMMARYBiotechnical varroa (Varroa jacobsoni) control methods are based on the principle that mites inside brood cells are trapped and then removed from the bee colony. In our experiments trapped mites were killed with formic acid. Worker brood used for trapping was retained and returned to the colonies. The observed percentage of mites trapped and killed by formic acid treatment was 87% and 89% in two experiments. The effectiveness could be predicted using prior knowledge on brood cell invasion behaviour, which thus proved to be valid for the design and improvement of trap-comb methods for ecological varroa control.

Interactive effect of reduced pollen availability and Varroa destructor infestation limits growth and protein content of young honey bees

Varroa destructor in combination with one or more stressors, such as low food availability or chemical exposure, is considered to be one of the main causes for honey bee colony losses. We examined the interactive effect of pollen availability on the protein content and body weight of young bees that emerged with and without V. destructor infestation. With reduced pollen availability, and the coherent reduced nutritional protein, we expected that V. destructor infestation during the pupal stage would have a larger negative effect on bee development than without infestation. Moreover, when raised with ample pollen available after emergence, infested pupae were expected not to be able to compensate for early losses due to V. destructor. We found that both V. destructor infestation and reduced pollen availability reduced body weight, abdominal protein level, and increased the head to abdomen protein ratio. The availability of pollen did indeed not result in compensation for reduced mass and protein content caused by V. destructor infestation in young bees after 1 week of their adult life. Both V. destructor and nutrition are top concerns for those studying honey bee health and this study demonstrates that both have substantial effects on young bees and that ample available pollen cannot compensate for reduced mass and protein content caused by V. destructor parasitism.

Effective biotechnical control of varroa: applying knowledge on brood cell invasion to trap honey bee parasites in drone brood

SUMMARYBiotechnical methods of varroa (Varroa jacobsoni) control are based on the idea that mites inside brood cells are trapped and can then easily be removed from a honey bee (Apis mellifera) colony. Trapping is most efficient using drone brood in otherwise broodless colonies. In theory, one trap-comb with drone brood is enough to achieve control. We designed and tested two methods using trap-combs with drone brood. In the first experiment, effectiveness of the control method varied considerably, from 67% to 96%. However, the observed effectiveness in each separate colony was similar to the prediction based on knowledge of behaviour of mites invading brood cells. Effectiveness depended on the number of drone cells that had been available for mite trapping. In the second experiment, we adjusted the method to improve production of trap-combs with drone brood, since this appeared to be crucial for trapping efficiency. The observed effectiveness of 93.4% demonstrates that trap-combs with drone brood can eff...

Effect of a home-made pollen substitute on honey bee colony development

Summary In 2001 and 2002, studies were conducted on a pollen substitute formulated for easy home preparation. Tests were done with free flying honey bee colonies. In 2001, pollen supply was restricted with pollen traps in 9 experimental colonies. Colonies were then equally divided among three treatments: (1) fed pollen substitute, (2) fed bee-collected bee bread, or (3) no supplement. In 2002 the design was similar except that the bee bread treatment was replaced with a control treatment without pollen trap or supplements. The pollen substitute was readily consumed by bees, and brood development (fraction of larvae achieving pupa) did not differ among treatments. In 2002, longevity of bees was highest in colonies fed pollen substitute even though this group had a pollen trap. The average concentration of haemolymph protein did not differ among treatments in 2001, but in 2002 this value was significantly highest in colonies without a pollen trap. The results of this study are applicable for honey bee colonies placed in greenhouses where pollen deficiency negatively affects bee longevity, brood rearing and pollination efficacy.

How honey bees of successive age classes are distributed over a one storey, ten frames hive

Summary In honey bee studies focusing on physiology, disease diagnosis or bio indication, bees are sampled from the colony. This raises the question of where in the colony samples must be taken from for specific study objectives. In this study we recorded where bees of known age are found in the hive. We recorded in a single brood box with ten frames in August that the mean proportion of bees of one (41%), two (23%), three (17%), four (11%) and five (8%) week old bees did not differ between frames. Additionally we found that there was a significant mortality of young bees in the first week after emergence. This may be partly due to the study set up but is also a natural phenomenon.

The fraction haemolymph vitellogenin of a honey bee colony, derived from a pooled haemolymph sample, a colony vitality parameter

The number of bees, amount of brood and haemolymph vitellogenin titre are parameters to establish the vitality of a honey bee colony. Increasing numbers of bees during summer until autumn; increasing amounts of brood in spring towards summer followed by a decrease; and low haemolymph vitellogenin titres in foraging bees and high vitellogenin titres in nurse bees and winter bees are typical courses over the bee season. In contrast to the number of bees and amount of brood, determined at the colony level, vitellogenin is determined in individual bees. To turn the factor vitellogenin from the mean of individual data into a colony parameter, a protocol was developed to determine the colony fraction vitellogenin in a pooled haemolymph sample of 30 bees, sampled from a defined location in the colony. This colony fraction vitellogenin is a parameter for honey bee colony vitality.