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Prevention of Apothecial Formation in Gloeotinia temulenta by Benzimidazole Compounds. John R. Hardison, Plant Pathologist, Crops Research Division, ARS, USDA, and Department of Botany and Plant Pathology, Oregon Agricultural Experiment Station, Corvallis 97331. Phytopathology 60:1259-1261. Accepted for publication 21 March 1970. DOI: 10.1094/Phyto-60-1259.

Methyl 1-(butylcarbamoyl)-2-benzimidazolecarbamate (benomyl) at 2 mg/92 cm² (2 lb./acre) in a single application at the soil surface over overwintered, infected seeds of Lolium perenne prevented formation of apothecia of Gloeotinia temulenta. Most apothecia were also suppressed by 0.5 or 1 mg of benomyl; 2-(4-thiazolyl) benzimidazole (thiabendazole or TBZ) prevented apothecial formation at 2 mg in one test, but failed in a second test; 2-(2-furyl)-benzimidazole (Bayer 33172) and 2,6-dichloro-4-nitroaniline (Botran or DCNA) suppressed apothecia at 10 and 8 mg, respectively. Fairly good control but incomplete suppression of apothecia was obtained with pentachloronitrobenzene (PCNB) at 20 mg and with a mixture of 20 mg PCNB plus 10 mg 5-ethoxy-3-(trichloromethyl)-1,2,4-thiadiazole (Terrazole). Benomyl eliminated apothecia during April-May from a single application made the previous November, December, or January in tests during 2 separate years. Seed infection was prevented after soil application and root uptake in L. perenne by benomyl at 60 mg but not by TBZ at 20 through 160 mg/600 ml of soil. Spraying the inflorescences before anthesis with benomyl at 10^–2, 10^–3, and 10^–4 did not prevent seed infection. Prevention of apothecial formation by low rates of benzimidazole compounds can eliminate ascosporic inoculum in grass fields, and may provide the first feasible chemical control of blind seed disease in grass seed crops.