When ‘Hass’ avocado trees produce an on-bloom and set an on-crop, the apical (and axillary) buds on the spring shoots, which would normally produce vegetative shoots during the summer and fall, are inhibited by the young developing fruit. Inhibition of summer shoot growth reduces the number of nodes that can bear floral shoots the next spring. It is important to note that summer shoots contribute > 60% of the spring bloom. The objectives of the research were to adapt prior trunk-injected and foliar-applied PGR treatments that showed promise in overcoming correlative inhibition (auxin > cytokinin) of summer vegetative shoot growth and inhibition of spring bud break (endodormancy, ABA > cytokinin) during the on-crop year as foliar- and irrigation-applied PGR treatments for use on ‘Hass’ avocado.
California’s research information regarding cultural practices for avocados is growing. However, the majority of published research provides input for grove management decisions based on a calendar year and on growing conditions typical of the semi-arid subtropical conditions of Southern California. Anecdotally, the cooler, moister growing conditions of northern growing areas including San Luis Obispo County result in different phenological timing for major events like bloom, fruit set and shoot flush. This project will develop comparative phenological calendars, develop an interactive web-based mapping program to allow storage and retrieval of digital images that record growth stages, and expand digital methodology results.
This research addresses the objective of the California avocado industry to develop and implement research programs that lead to increased grower profitability.