Insect pollination and production in two old varieties of Damas plums (Prunus domestica L.)

Self-incompatibility is common in domestic plums and cross-pollination by bees is considered to provide optimal pollination. The purpose of this study was to determine the relative influences of insects, wind, and gravity in the pollination and production of two plum varieties, Purple Damas and Yellow Damas, and to identify actual pollinators. Fruit sets on branch sections covered with cages (1) closed to insects and wind, or (2) closed to insects only, were compared to fruit sets on branches where (3) flowers were readily accessible to pollination by indigenous insects; in this last case, fruit sets were 42% for Purple Damas and 15% for Yellow Damas. These figures are significantly higher than those obtained inside the cages and are sufficient to allow commercialisation. Relative contributions of insects, wind, and gravity to pollination were estimated to be respectively 76%, 16% and 8% in Purple Damas, and 52%, 28% and 21% in Yellow Damas. Indigenous pollinators can adequately pollinate these fruit trees in the absence of the honey bee, Apis mellifera L.