Germination and sporulation of Colletotrichum acutatum on symptomless strawberry leaves

The germination and sporulation of Colletotrichum acutatum were characteriz ed over time on strawberry leaves (cv. Tristar) and plastic coverslips incu bated at 26 degreesC under continuous wetness. Conidia germinated within 3 h after inoculation and formed melanized appressoria with pores by 9 h afte r inoculation. Host penetration was not observed up to 7 days after inocula tion. Production of secondary conidia on conidial and hyphal phialides bega n within 6 fi after inoculation. Secondary conidiation was responsible for up to a threefold increase in the total number of conidia within 7 days aft er inoculation. Primary conidia and hyphae began to collapse 48 h after ino culation, whereas melanized appressoria remained intact. These findings sug gest that appressoria and secondary conidia of C. acutatum produced on symp tomless strawberry foliage may be significant sources of inoculum for fruit infections.