Increasing off-season snake fruit (Salacca zalacca) yield by preventing fruit set failure with different exogenous auxin spray

Snake fruit blooms every three months, but only one to two of the flowering seasons result in fruit production. Failure of fruit set causes the fruit harvest seasonally. Therefore, the aim of this research was to increase off-season production by preventing the failure of fruit set with various exogenous auxin spray. The research was conducted in the snake fruit orchard at Bebandem Sub-District, Karangasem Regency, Bali Province, Indonesia, from February to November 2019. The experiment was designed as a nested factorial with a randomized block design. The treatment consisted of three types of auxin with a specific concentration for each, IAA at 0, 25, 50 and 75 ppm, IBA at 0, 50, 100 and 150 ppm, and NAA at 0, 50, 100 and 150 ppm. The IAA, IBA, and NAA were sprayed on the flowers and leaves 3 times in March, April, and May. The results showed the highest percentage of fruit set, fruit weight per tree, and weight per fruit obtained with IAA treatment were 59.80 %, 2,612.91 g, and 91.06 g, respectively. These results were not statistically different to those of the IBA and NAA. Furthermore, the IAA concentration of 25, 50, and 75 ppm produced a significantly higher percentage of fruit set compared with the control. The increased fruit set in the IAA, IBA and NAA treatments resulted in better yield than the control. The novelty of this result is that spraying snake fruit with IAA, IBA and NAA can prevent the failure of the fruit set. Therefore, IAA, IBA, and NAA are recommended to be applied to increase off-season fruit production of snake fruit.