Fungicide control of head smut (Sporisorium reilianum) of sweetcorn (Zea mays)

Abstract A field trial was carried out to compare the efficacy of the fungicides carboxin + thiram (Vitafio ® ), carbendazim (Prolific ® ), tebuconazole (Raxil ® ), propiconazole (Tilt ® ), fiutriafol + imazalil sulphate (Vincit™), and azoxystrobin (Amistar ® ) as seed applications for the control of head smut of sweetcorn (Zea mays) , caused by the fungus Sporisporium reilianum (Sphacelotheca reiliana). The trial was carried out in the Poverty Bay region of New Zealand in a field that had a previous history of head smut. Carbendazim, fiutriafol + imazalil sulphate, propiconazole, and azoxystrobin seed treatments resulted in significantly greater plant numbers and increased early plant growth compared with the untreated experimental control, carboxin + thiram, and tebuconazole treatments. Plots in the control and carboxin + thiram treatments had a relatively high number of stunted plants (<10 cm) 1 month after sowing (7.6% and 14.9% respectively). Carbendazim, tebuconazole, propiconazole, fiutriafol + imazalil sulphate, and azoxystrobin seed treatments all produced low numbers of stunted plants (0.4–3.1%). Of the plants in the untreated control plots, an average of 8.7% were infected with head smut at harvest maturity. Seed treatment with carboxin + thiram didnotreduce numbers of smutted plants compared with the untreated control. All other fungicides reduced the proportion of diseased plants. The most effective were propiconazole and fiutriafol + imazalil sulphate, which respectively gave 2.3% and 2.4% plants infected with head smut. Carbendazim, tebuconazole, and azoxystrobin were slightly less effective reducing infection to 5–6%. Fiutriafol + imazalil sulphate and propiconazole both offer alternatives to carboxin + thiram for control of head smut of sweetcorn.