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.

The research was conducted on 6 cultivars over three consecutive years. Nectar production of quince was found to be small compared to other temperate zone fruit tree species, since quince flowers contained 1.07 - 0.06 mg of nectar on average. Sugar concentration ranged between 21-27 % on average in different years with a range between 9-47.5 %. There was a significant negative correlation between the amount of nectar and its sugar concentration, but no definite difference was established between the ne ctar production of quince cultivars. In spite of this, bee visitation was highly intense about 5.5 bee visits were counted on average at 50 open quince flowers in 10 minutes and about 9.7 flowers out of 50 were visited. This equals about 7 bee visits per flower per day in good weather. Some cultivars tended to be more and less visited by honeybees. Most honeybees tended to collect pollen (51.6 % in average for the 3 years) and usually fewer gathered only nectar (19.9 %), while the rest had a mixed foraging behaviour gathering both (28.5 %). There were slight differences in the foraging behaviour of honeybees on some cultivars, but these differences were not always consequent in consecutive years. Quince is highly sensitive to partial and/or complete limitation of the insect (bee) pollination period. Complete limitation of insect pollination resulted in no yield and partial limitation of the insect pollination period depressed the final set and yield by at least 60-70 % or more. Significant correlation was established between the intensity of honeybee visitation and the consequent yield of quince. As much as 4-5 or 8-10 honeybee visits are needed per day on one flower to achieve the required optimal fruit set that has been declared in the literature to be 20-25 % for quince.