Sunday, March 1, 2009
Avocado Pollination by Honeybees
This is the season for avocado pollination in our little town of Fallbrook, known as the avocado capitol of the world. Avocado trees come from Mexico where a native stingless bee provides the pollination. Since that pollinator doesn't live here, honeybees have taken over the job. Every fruit produced depends on pollen being transferred from one flower to another, so honeybees become the most valuable citizens in town during the few weeks when the trees are in bloom.
Avocados have an odd system of pollination to insure cross pollinization. Each of the inconspicuous green/yellow flowers has both male and female parts, but only one sex is open at a time to prevent self fertilization. There are two kinds of trees, A and B types. The A type trees have their flowers open in the mornings as females. The flowers close by afternoon, and remain closed until the following afternoon, when they reopen with the male parts now producing pollen. The B type trees open their flowers as female in the first afternoon, they close and reopen as males the following morning. Each flower only opens twice. If a grove is properly planted with both types of trees, and if pollinators are present then a good set of fruit is likely. Honeybees do the vast majority of the pollination here, but wild bees, flies, wasps and even hummingbirds are also seen working the flowers.
Fallbrook was founded by the Reche family in the late 1800's, and they just happened to have been beekeepers. Back then the landscape was dominated by the native chaparral plants which are superb honey producers. At one time San Diego County was the number one honey producing county in America. Today, with only about 10% of the chaparral left, this is no longer the case. Urbanization has forced those beekeepers that are left to flock to areas like Fallbrook where bees are still welcome. So a symbiotic relationship has formed between growers and beekeepers; we both need each other.
Read more about avocados and bees here or Wikepedia