DISCUSSIONSolar UV radiation is one of the main environmental factors thatcan kill conidia of several fungal pathogens (42–44). This studyshows that conidia produced in dark-grown cultures and washedfree of the surrounding mucilage are all inactivated by a fewhours of exposure to UV irradiance equivalent to that found innature. While this was true for all five isolates, we observedsome variability in UV tolerance among them. Variation inconidial tolerance to UV-B radiation was previously observed inother fungal species and at least part of it has been explained bythe adaptation of the isolates to different environmental UV lev-els associated with the sites of origin (25,45–47). Our resultsindicate that in C. acutatum variation in conidial tolerance to UVoccurs even among strains isolated in the same habitat (commer-cial orange orchards in S~ao Paulo State) and in sites close toeach other.Growth of C. acutatum colonies under low irradiance of visi-ble light increased conidia and mucilage production and also thetolerance to UV radiation of the produced conidia. The increasein conidia production induced by visible light was previouslyobserved in other fungal genera including Colletotrichum(15,48). Exposure to light also increased mucilage productionand changed its absorption spectrum. Mucilage produced by thecolonies exposed to light present absorption peaks in UV-C and