The effect of succinamic acid 2,2-dimethylhydrazide (Alar) on shoot growth and fruit quality of Santa Rosa plums

Succinamic acid, 2,2-dimethylhydrazide (Alar) was applied at various postbloom dates and concentrations to Santa Rosa plum trees in 1970 and 1971. Alar sprays of 2000, 4000, and 8000 ppm applied at fruit pit hardening in 1970 resulted in a significant reduction in shoot length with no significant effect on shoot diameter. An Alar spray of 2000 pmm applied in 1970 resulted in larger fruit; however, the same spray concentration applied in 1971 resulted in smaller fruit. 2000 ppm Alar applied at full bloom resulted in a reduction of soluble solids and pH, and an increase in titratable acids. Alar applied at 2000 ppm two weeks after full bloom, had no effect on fruit quality. The 2000 ppm Alar applied at fruit pit hardening resulted in an increase in soluble solids and pH with a trend towards decreasing titratable acids. A trend towards firmer fruit occurred regardless of the application date of Alar.