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An experiment was carried out to determine the effect of 2,4-D isopropyl ester and NAA on fruit size as well as preventing pre-harvest fruit drop of local tangerine in
Jahrom. Seven year old trees of local tangerine were sprayed with aqueous solutions of 2, 4-D isopropyl ester at 0,4,8 and 12 mg/l 3, weeks after full bloom for improving fruit
size. Highest yields and largest fruits were obtained in 12 mg/l 2,4-D treatment. Apart from reduced vit. C content other fruit characteristics were not affected. Pre-harvest fruit
drop is a serious problem in Jahrom local cultivar of tangerine. Eight year old trees were sprayed with aqueous solutions of 2,4-D isopropyl ester at 0, 8, 16, 24 and NAA
potassium salt at 15 and 30 mg/l on Dec. 21,1995 and Jan. 4, 1996. Spray treatment with NAA at a concentration of 30 mg/l reduced pre-harvest fruit drop by 56% as compared with the untreated control.