Preharvest Application of Sulfur as Pesticide on Fresh Hull and Kernel of Pistachio (Pistacia vera L.)

In recent years, sulfur has been shown to be effective in controlling pistachio psylla. In this study, the effect of sulfur foliar application as psylla pesticide on fresh fruit and kernel of three cultivars of pistachio was determined and compared with two commercial pesticides. Refinery micronized and mineral sulfur were applied at two concentrations of 30 and 60 kg/1000 L of water. The quality of fresh pistachio hulls and kernels were investigated. In ‘Fandoghi’ cultivar, all sulfur treatments reduced the kernel moisture. The firmness and water activity of hulls and kernels were significantly affected. All sulfur treatments decreased hull lightness in ‘Fandoghi’, while it increased in ‘Akbari’ and ‘Ahmadaghaei’ cultivars. Reduction of hull chroma was observed in some cases in all cultivars. Hue of hulls was not affected by the treatments. Lightness, chroma and hue values of the testa of kernels were not affected in ‘Fandoghi’ and ‘Akbari’. In ‘Ahmadaghaei’, refinery micronized sulfur increased the testa lightness and hue and decreased chroma probably because of the softer texture of hull in ‘Ahmadaghaei’ which breaks more easily during harvest practice. Sulfur treatments positively influenced appearance and general acceptance of ‘Ahmadaghaei’ fruits. The taste and aroma of pistachios were preserved in most of treatments. High concentration (60 kg/1000 L) of both sulfur types enhanced the ethylene production in ‘Ahmadaghaei’ which was almost same as the unripe fruit because sulfur treatments reduced the percentage of unripe fruit. In ‘Ahmadaghaei’, refinery micronized sulfur treatments increased the respiration rate.