Some physiological changes of fresh pistachio upon foliar application of sulfur

The application of sulfur as a pesticide is a strategy in plant protection, but in addition to their many benefits for pest control, pesticides may affect crop characteristics. In this study, movento (0.5 L/1000 L), confidor (0.4 L/1000 L), and refinery micronized (R) and mineral (M) sulfur (30 and 60 kg/1000 L in water) were sprayed on pistachio trees of the cultivar ‘Ahmadaghaei’ twice (in middle May and after 50 days) for controlling the psylla. Pistachios were harvested in late September and stored at 4 °C for 25 and 50 days. The effect of pesticides on hulls and kernels was then evaluated. Weight of pistachios, phenolic content of kernel, and chlorophyll and carotenoid contents of hull and kernel declined over time, while phenolic content of hull displayed an increasing trend. DPPH scavenging capacity of hull and kernel remained stable over time. Refinery micronized sulfur at both concentrations caused a higher weight loss on day 25 but it was similar to control after 50 days. It caused higher chlorophyll and lower carotenoid of hull and kernel. Mineral sulfur at both concentrations caused higher chlorophyll content of hulls. All sulfur treatments reduced the antioxidant activity of the hull and kernel, while elevating the hull phenolic content. Movento and Confidor pesticides stimulated loss of weight. Although the chemical pesticides and sulfur cannot easily penetrate the kernel, the physiological status of the hull and the whole plant may influence the kernels and the yield.