Efficacy of calcium polysulfide suspension against Golovinimyces cichoracearum , the causal agent of powdery mildew of cucumber

This study assessed the efficacy of calcium polysulfide suspension concentrate (SC) against cucumber powdery mildew (Golovinomyces cichoracearum) under glasshouse conditions in Varamin and Pishva, Tehran Province. A randomized complete block design included eight treatments – calcium polysulfide at 1–5 ml/L, reference fungicides tetraconazole (Domark® .4 ml/L) and trifloxystrobin (Flint® .2 g/L), and an untreated control – with four replications per treatment. Foliar sprays began at first symptom appearance and continued at 5–10-day intervals. Disease severity was rated using the Horsfall-Barratt scale, Disease Severity (DS), and Area Under the Disease Progress Curve (AUDPC). ANOVA and Duncan’s test (p = .01) revealed significant treatment differences at both sites. In Varamin, 3–5 ml/L calcium polysulfide reduced AUDPC by 70–87.5%, matching reference fungicides. In Pishva, reductions ranged from 74–84.5% at these rates. Concentrations of 3–4 ml/L provided reliable control comparable to standards, positioning calcium polysulfide as a low-risk alternative for rotations every 7–14 days.