THE APPLICATION OF POLLEN can be separated into two distinct areas. The first area is the issue of timing. At what stage of blossom development should pollen be applied to the orchard? The second issue is the manner in which pollen is to be applied; beehive pollen dispensers; ATV or Helicopter applications.
In general, tree fruit flowers remain receptive to pollination for 12 to 72 hours after the flower has opened, depending upon the tree fruit variety, the nutritional status of the tree as well as environmental conditions. Flowers remain receptive to pollination for a shorter period of time when weather conditions are hot and dry.
During cool, moist conditions, flowers remain receptive to pollination for a longer period of time, but this longer receptivity is quite often offset by the slower growth of the pollen tube which occurs during cool weather. The EPP (Effective Pollination Period) is most directly dependent upon the nutritional condition of the orchard and the temperature.
It is important to closely examine the bloom of your orchard.
1. To assess the stage of development
2. To assess the coordination of the bloom between the pollinizer variety and the main crop variety.
3. A sampling of flowers should be made to assess any frost damage that may have occurred.
Determining the Stage of Development
It is fairly easy to determine the stage of development your bloom is in, as well as the flowers receptivity to pollination. Pick a newly opened flower from the block you want to pollinate. Examine the anthers; the little yellow sacks or in the case of Pears, the pink to red sacks which surround the stigmas, the center of the flower. These are the flower's anthers, the sponge like sacks which hold the pollen.
To the naked eye, the anthers have a smooth, deeply colored appearance before they have begun to dehisce (shed) their pollen. Under the microscope, the anthers have an appearance similar to that of a sponge, with a pock-marked surface which retain the pollen grains.
When the anthers have dehisced their pollen, they begin to shrivel and turn brownish in color. From the time the flower first opens, to the time that the anthers dehisce their pollen, this is the period in when the flower is the most receptive to pollination.
Number of Applications
One problem that can exist even during ‘normal years’, is that there may be little coordination between the bloom of the main crop and that of the pollinizer variety. This may be true in specific areas of the orchard or across the entire block.
To combat this problem, we recommend that pollen be applied with two or more applications over the course of the bloom period. The reason for this recommendation, is that even during seasons when flowers of a particular section of trees or for the entire orchard are blooming fairly evenly, there is still a timing difference between the opening, receptivity and pollen availability between flowers.
By planning for two or more applications of pollen to be applied to the orchard, most of the bloom can be effectively covered. In cooler climates, the opening of flowers may be more extended, requiring a longer pollen application period. In warm climates, be prepared to quickly apply as much pollen as possible, for the bloom may not remain receptive to pollination for a long period of time.