Effects of selected insecticide formulations, phased application and colony management strategies on honeybee mortality in processing sweetcorn.
Catherine S Williams
Nectar secretion rates and standing crops were investigated in the field in Phacelia tanacetifolia. an annual herb which is visited by nectar-collecting bees. Flower age was an important correlate of secretion rate: 4 h- and 7 h-old flowers had higher secretion rates than older and younger flowers. Flower stage also explained significant variation in secretion rate, but less than age, with which it was correlated. Although secretion rates varied significantly with flower stage, standing crops did not, suggesting higher rates of depletion in flowers with higher secretion rates. The flower-probing choices of honey bees (Apis mellifera) and bumble bees (Bombus spp.) on first arrival on an inflorescence were recorded. Bees probed flowers in rapidly-secreting flower stages more often than would be expected by chance. These findings support the argument that if the probability of a visit to a given flower at a given time depends on its nectar content at that time (the standing crop), the number of visits received by that flower over a given interval depends on its secretion rate. In the case of P. tanacetifolia, the visitation rate changes over the life of a flower. as its secretion rate changes.