Plant Growth Regulators for Avocado Production

Plant growth regulators (PGRs)are the most powerful tools available for manipulating tree growth and yield in an established orchard. Understanding the phenology and physiology of the avocado (Persea americana Mill.)is critical for selecting the correct PGR and for properly timing the application annually to consistently elicit the desired response. Results from two recent multi-year PGR experiments have provided evidence of promising PGR strategies for increasing 'Hass' avocado yield and fruit size. Gibberellic acid (GA3)(25 mg/L)applied at the cauliflower stage of inflorescence development or applied at the end of June-beginning of July significantly increased total yield and yield of large size fruit (packing carton sizes 60-40, 178-325 g/fruit)in kilograms per tree as 2-year average and 2-year cumulative yield (P 0.03). Benzyladenine (BA)(25 mg/L)applied at anthesis or GA3 (25 mg/L)applied in mid-July followed by prohexadione calcium (ProCa)(125 mg/L)30 days later ignificantly increased the yield of larger size fruit (packing carton sizes 40-28, 270-446 g/fruit)in kilograms per tree as 2-year average yield (P = 0.0069 and P = 0.0564, respectively)and 2-year cumulative yield (P = 0.0120 and P = 0.0624, respectively)without reducing total yield or yield of fruit of packing carton sizes 60, 48 and 40. These strategies will be tested in additional orchards.