THE PLUM TREE CONDUCTED POLLINATION WITH THE BEES HELP

Valentina Cebotari, I. Buzu

Abstract
    The research purpose was to identify an efficient mecanism (modality) of pollination, with the help of bees, of the plum trees culture in intensive orchards. It was done an experiment, in order to test comparative the three methods (ways) of hives placement on the ground at the plum trees pollination, in 3 analogous intensive sectors, with five sorts of plums, that are compatible to the pollination, of 10 hectares each, which were located at a distance of 600 m from each other. In all sectors of the orchard, bee colonies have been assigned with the charge of 3 families/ha. In the first sector (I batch - control) of orchard, hives with bee colonies were located at the edge of the orchard (sector) in the front side of rows. In the second sector (II batch), the hives were located on the technologic road which separated in the centre the sector of orchard, perpendicular to fruit trees rows. The distance between hives was 5 m from each other. In the third sector of the orchard (III batch), the hives were located, inside of the orchard, between the tree rows, in line, at a distance of 100 m from each other and over every 7th row of trees. In each experimental batch were rated the free entomophily pollination results (crossed) and isolated (self pollination). It was found that, in the I batch, frequency of bees visit at tree blossom, has been weaker in the first days of hives placement, but was quite good in batches II and III, even from the first day. With the increase of air temperature from 14 up 18oC, in all batches was registered a growth tendency of bees visits frequency at blossom. The results of the experiment, have shown that free pollination (cross) entomophily (with predominant participation in proportion of 90 - 95% of honey bees) of plum trees in the orchard ensures the flowers fertilization, depending of beehives location on the field, at the level of 19.0 - 41.5%, that is 17.3 - 33.6 times higher, compared with the isolated pollination - self pollination (1.1 - 1.2%). Therefore, it has been confirmed, once again, the conclusion of many researchers, that, the participation of honey bees at pollination of apple's culture is an indisputable necessary measure. Uniform and proportional placement of bee hives inside the orchard, between the rows, in line, at a distance of 100 m from each other, and over every 7th row of trees, ensures a significant increase, compared to the witness batch (located at the orchards edge), of bees visit frequency to the flowers is 2,3 times more (td = 14.3; P<0.001), of the bees flight intensity (with and without balls) with 23,1 - 40.9% (td = 5.8 - 6.9; P < 0.001), of collected pollen quantity - with 57.4 % (td = 10.9; P < 0.001), of flowers fertilizing degree - with 2.1 times (td = 14.4; P < 0.001) and, compared to traditional methods of hives placement (on the technological roads of the orchard), ensured the growth of bees visits frequency on blossom - with 74.4 % (td = 12.9; P < 0.001), of collected pollen quantity from apple - with 17.5 % (td = 2.4; P < 0.05), and of the flowers fertilization degree - with 2.2 times (td = 12.8; P < 0.001).

Key words: pollination, plum, honey bees, placement, bee hives