The objectives of this study were to evaluate the effect of light regimes on the mycelial growth of Fusarium moniliforme in fungicide-amended culture medium; to select the best light regime to detect F. moniliforme in treated corn (Zea mays) seeds and the variable to be used; and the effect of treatment on seed health and physiological quality. The fungicides evaluated were: fludioxonil + metalaxyl-m (three concentrations), difenoconazole, acibenzolar-S-methyl e captan + thiabendazole. For evaluation of mycelial growth, fungicides were added to the culture medium at three concentrations (100, 10 and 11 æg/ml). Inoculated plates were incubated at 20±2 ºC, under three light conditions: total darkness, white light and near ultraviolet light (12 h of light/12 h of darkness). In order to evaluate the effect of light on fungicide-treated seeds, a deep freezing test was carried out and seeds were incubated under the same conditions as the former test; seed health test was evaluated by measuring disease incidence and severity. Two seed samples were treated and submitted to seed health, germination, seedling emergence rates in greenhouse and cold tests. In vitro tests indicated that white light decreased the effect of the active ingredients fludioxonil + metalaxyl-m and captan + thiabendazole. The health test did not show this effect. Severity of the disease was found to be the most sensitive variable to distinct efficacy of fungicides in controlling F. moniliforme in corn seeds. The results found for both the two seeds samples suggested that: a) Fusarium moniliforme does not affect the physiological quality of corn seeds; b) the fungicide that controlled the pathogen in seeds was captan + thiabendazole, followed by fludioxonil + metalaxyl-m (97.2 g + 147.86 g/l); c) Pythium sp. was controlled by captan + thiabendazole and by fludioxonil + metalaxyl-m at the three concentrations.
