Fungicidal effect of hydrogen sulfide, iodine, and peroxy-acetic acid on tuber potato dry rot disease

The current study investigates potato dry rot disease caused by Fusarium oxysporum, Alternaria alternata, and other fungi during storage and marketing. Both in vitro and in vivo experiments were conducted to evaluate the efficacy of iodine, hydrogen sulfide, peroxy-acetic acid (PAA), and the fungicide Diabolo® 10% SL in controlling F. oxysporum and A. alternata, the main pathogens associated with dry rot. Amendment of the growth medium with any of the tested compounds significantly reduced the mycelial growth of the pathogens. The greatest reduction was observed with H₂S, followed by iodine, while PAA showed the lowest inhibitory effect. Complete inhibition of fungal growth occurred when Diabolo® 10% SL (150 ppm) was incorporated into the medium. A synergistic effect was recorded when PAA was combined with either H₂S or iodine. The highest inhibition was achieved when 1% H₂S or iodine was mixed with PAA (containing 4 mg/L H2O2 and 0.4 mg/L acetic acid). Pre-planting treatment of potato tubers (cv. Cara) with iodine, H₂S, PAA, or Diabolo® 10% SL also significantly reduced disease incidence (DI%) and disease severity (DS%) of wilt symptoms caused by F. oxysporum and A. alternata. Among the treatments, the fungicide and H2S showed the highest effectiveness. The combination of PAA with iodine or H2S enhanced their individual effects, with the H₂S + PAA mixture providing greater disease reduction than the iodine + PAA mixture. Overall, the study demonstrates that mixing PAA with either iodine or H2S can safely protect stored potato tubers and effectively control dry rot pathogens.