The duration of effective bee pollination period was limited by caging flowering branches for shorter or longer time. In the case of self-fertile apricots even a partial limitation of the effective duration of bee pollination period significantly reduced the fruit set and the yield. This is because pollen dehiscence of anthers and the receptive period of stigmas do not overlap in time within the individual flowers. Accordingly, additional bee pollination (moving bee colonies to the orchards at blooming period) is needed to get a profitable yield when bee visitation of plantations is not abundant enough for some reasons.

Peach varieties grown in Hungary are self-fertile and set sufficient fruit under favourable weather conditions by natural self-pollination. The literature as well as our observations, suggests that bee pollination enhances fruit set even in selffertile varieties. The nectar production (0.30-9.09 mg/flower) and its dry matter content (12.5-58.1 %) varied widely by variety and sampling date. In relation to other stone fruit species peach was relatively low in nectar production (2.2 mg/flower) as well as in dry matter content (30.5 %). In spite of the low nectar, honeybees frequently visited production peach flowers. The reason for that is due to the early blooming time of peach, when honeybees have less available resources. Under favourable weather conditions (sunshine, calm warm weather) 20 % of the flowers on a branch were visited within a 10-minute period. Thus the same flower received several visits during one day. About half the bees visiting peach flowers were nectar gatherers. Another 27 % were pollen collectors and the remaining 23 % displayed mixed behaviour of collecting both pollen and nectar. The limitation of honeybee visits impaired the fruit set less in peaches than in other stone fruit species. Nevertheless, fruit set was markedly different between open flowers and isolated (bagged) flowers.