Regression models for determining infection periods of apple white rot were developed based on conidial germination and appressorium formation of Botryosphaeria dothidea. A total of 120 apple fruits were inoculated with the fungal conidial suspension and subjected to 6 temperatures and 10 wetness periods. Conidia germinated and produced appressoria, exhibiting swollen tips of germ tubes on the fruit surface. Conidial germination (G) increased with temperature (T) and wetness period (W), and was described as G = -89.273 + 7.649T + 7.056W - 0.109T2 - 0.085W2 - 0.066TW (R2=0.75). Less than 2 hr of wetness period were enough for conidia to germinate at 25 to 30