The effects of culture media, temperature and pH on in vitro growth and sporulation of Pyrenophora semeniperda were examined to determine optimal conditions for abundant production of conidia. Radial growth and sporulation (expressed as conidia cm −2 and conidia colony −1 ) were optimal on modified alphacel culture medium (oatmeal, 10 g; MgSO 4 . 7H 2 O, 1 g; KH 2 PO 4 , 1·5 g; NaNo 3 , 1 g; coconut milk 50 ml; agar, 17 g; distilled H 2 O, 1 l). Growth occurred over the temperature range 5 to less than 35 °C and was optimal at 23·2±0·5°. Sporulation occurred over the range 10 to 30° and was optimal at 19·2±0·05° when expressed as conidia colony −1 , and 18·3±0·3° when expressed as conidia cm −2 . The pH for maximal growth was 4·7±0·5, while that for maximal sporulation was 5·4±0·2 when expressed as conidia colony −1 , and 5·7±0·1 when expressed as conidia cm −2 .