The effect of fungicidal seed treaters on germination of rye ergot (Claviceps purpurea (Fr.) Tul.) sclerotia and on ascocarp formation

The inhibitory effect of the fungicidal seed treaters Baytan-Universal 19.5 WS (triadimenol+fuberidazole+imazalil), Panoctine 35 LS (guazatine), Divident Star 036 FS (difenoconazole+cyproconazole), Premis 25 FS (triticonazole), Kinto 80 FS (prochloraz+triticonazole), and Jockey 198 FS (fluquinconazole+prochloraz) on the germination of ergot (Claviceps purpurea (Fr.) Tul.) sclerotia and ascocarp formation was studied in laboratory and field conditions. Rye (Secale cereale L.) seed, contaminated with ergot sclerotia, was used for the tests. Fungicide rates recommended for rye seed treatment were applied.Experimental evidence from 2 yr suggests that the seed treaters tested inhibited and delayed sclerotial germination. In laboratory conditions, the most effective were found to be Baytan-Universal 19.5 WS and Jockey 198 FS, whose application produced a complete suppression of sclerotial germination and ascocarp formation. However, under field conditions, 12.0–41.8% of Baytan-Universal-treated sclerotia germinated. Panoctine 35 LS and Kinto 80 FS were fairly effective: as few as 1.0–12.8% of sclerotia germinated, and the germination was 9–21 days later than that of the untreated. The other seed treaters, depending on conditions and the year, suppressed sclerotial germination by 23.0–94.5%. Treated sclerotia formed significantly fewer ascocarps compared with the untreated where 36.5–82.0% of sclerotia germinated, and each sclerotium formed on average 4.3–7.0 ascocarps.