Isolates of Mycosphaerella fijiensis var. difformis sporulated differently on 3.63% on Mycophil agar at 20, 25, and 30ÂºC. A large number of viable spores (2.1 â€“ 13.1 Ã— 106 conidia plate-1 maximum) were produced in 24 days by cultures incubated at 20ÂºC under 2.5 W m-2 of continues, cool-white, fluorescent light. A reliable quantitative inoculation technique was developed using a clean suspension of conidia produced under these conditions. Typical symptoms of black Sigatoka disease appeared on young banana leaves after a minimum of 16 days in a growth chamber at 25 Â± 1ÂºC.