Inducing flowering delay in apricot cv. Shahroudi by ethephon and gibberellic acid

Control of floweing time in apricot trees is very important where spring frost damage is of high risk. Application of plant growth regulators during autumn has been suggested for controlling bloom date. This experiment was conducted during 1999-2001 to examine the effects of application of different concentrations of ethephon and gibberellic acid (0,50, 100,200,300 mglit-1 in 3 dates (end of August, September, and October) on delay of flowering in apricot Shahroudi cultivar. A factorial experiment was laid out in completely randomized-block design with 3 replications. Compared to the control, results showed that 100 mglit-1 of ethephon applied at the end of October, delayed full bloom approximately 3 days (2000) and 7 days (2001). Gibberellic acid applied at 300 mglit-1 at the end of August, delayed full bloom about 5 days (2000) and at the end of September, 10 days (2001). During both years, application of gibberellic acid and ethephon at the higher concentrations resulted in a lower percentages of flower opening and fruit set.