Alternate bearing is typically initiated by adverse climate. Once initiated, in the absence of additional environmental constraints affecting crop load, the bearing status of an orchard alternates between ON and OFF years, with ON years exhibiting less vegetative growth than OFF years. This biennial cycle, however, can be reset by adverse environmental conditions affecting bloom and fruit set. Adverse conditions 8-10 weeks prior to bloom may cause abortion of female flower parts, resulting in a high proportion of staminate (male) flowers that do not give rise to fruit. Additionally, adverse weather conditions at bloom may impact pollination and subsequent fruit set. Any conditions resulting in loss of crop during an anticipated ON year may render the season an OFF year.
For a fuller discussion of this topic, see the full article by Carol Lovatt at:
The Topics in Subtropics Newsletter