Prevention of black spot disease in persimmon fruit by gibberellic acid and iprodione treatments
1995
Perez, A. | Ben-Arie, R. | Dinoor, A. | Genizi, A. | Prusky, D.
Black spot disease (BSD) in persimmon fruit, caused by Alternaria alternata, develops primarily in the high humidity environment beneath the calyx. Three treatments with gibberellic acid (GA3, 20 micrograms/ml) applied during fruit development at 30, 20, and 10 days before harvest, reduced decay more effectively than the single commercial treatment of GA3 (50 microgram/ml) applied 10 days before harvest. As a result of GA3 treatment, the calyx of the fruit remained erect till harvest. The correlation coefficent between BSD under the calyx and calyx erectness was r = -0.72. Persimmon fruits treated with GA3 in the orchard and stored at 0 C for 3 mo showed less fruit area becoming covered with black spot during storage compared with untreated fruit. Increasing the number of sprays from one to three resulted in a decreased infected area. Sprays of GA3 also inhibited fruit softening, with a correlation coefficient of r = 0.63 between decayed area and fruit firmness. GA3 at concentrations up to 200 microgram/ml had no effect on fungal development in vitro and in vivo on inoculated fruits. GA3 apparently affects decay development by enhancing resistance of the fruit. Preharvest treatment with GA3 and the fungicide iprodione further reduced the percentage of fruits unmarketable due to BSD.
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