The wheat pathogenZymoseptoria triticican respond to light by modulating its gene expression. Because several virulence-related genes are differentially expressed in response to light, different wavelengths could have a crucial role in theZ. tritici–wheat interaction. To explore this opportunity, the aim of this study was to analyze the effect of blue (470 nm), red (627 nm), blue–red, and white light on the in vitro and in planta development ofZ. tritici. The morphology (mycelium appearance, color) and phenotypic (mycelium growth) characteristics of aZ. triticistrain were evaluated after 14 days under the different light conditions in two independent experiments. In addition, bread wheat plants were artificially inoculated withZ. triticiand grown for 35 days under the same light treatments. The disease incidence, severity, and fungal DNA were analyzed in a single experiment. Statistical differences were determined by using an ANOVA. The obtained results showed that the different light wavelengths induced specific morphological changes in mycelial growth. The blue light significantly reduced colony growth, while the dark and red light favored fungal development (p< 0.05). The light quality also influenced host colonization, whereby the white and red light had stimulating and repressing effects, respectively (p< 0.05). This precursory study demonstrated the influence of light onZ. triticicolonization in bread wheat.