Alternaria spores germinate within 2 hours over a wide range of temperatures but at 26.6-29.4 °C (80-85 °F) may only take 1/2 hour. Another 3 to 12 hours are required for the fungus to penetrate the plant depending on temperature. After penetration, lesions may form within 2–3 days or the infection can remain dormant awaiting proper conditions (60 °F) and extended periods of wetness. Alternaria sporulates best at about 26.6 °C (80 °F) when abundant moisture (as provided by rain, mist, fog, dew, irrigation) is present. Infections are most prevalent on poorly nourished or otherwise stressed plants.