Fruit drop prevention in local tangerine by growth regulators in response to application time

The aim of the present study was to evaluate the effects of some growth regulators on local tangerine (Citrus reticulata Blanco) fruit abscission in late summer, and also to note the proper time of application to prevent late summer fruit drop. Trees were sprayed with different concentrations of 2,4-D (2,4-dichlorophenoxy acetic acid) and NAA (α-naphthalene acetic acid) alone or combination of of both, four times from September to December at one month interval. The combination of 20 mg l⁻¹ 2,4-D + 30 mg l⁻¹ NAA, 10 mg l⁻¹ 2,4-D + 15 mg l⁻¹ NAA and 10 mg l⁻¹ 2,4-D, among other treatments, had the better effects in preventing fruit drop. Application of growth regulators during September prevented fruit drop in the month of December, which was statistically significant (α < 0.05).