These are blown or splashed onto nearby susceptible plants which become infected. Dormant fungal structures in roots or stems begin growing again when circumstances are favorable, and cause additional damage to plants they have previously infected. Environmental conditions significantly influence the development of root and crown rot. When the soil is sodden with moisture for extended periods, fungi such as Pythium and Phytophthora are active and infect plants. Drier soil conditions, but with high relative humidity, are favorable for Rhizoctonia .
Most woody plants grow best when the light intensity is high.
Conditions that maintain high humidity around plants such as cloudy weather, excessive shading, and plants growing too close together also promote disease. Plants growing in soils that are fine textured and poorly drained are more prone to root and crown rot. Adequate soil fertility promotes seedling vitality, but applying fertilizers with high nitrogen composition induces excessive succulent new growth, prolonging the period when plants are vulnerable to fungal infection. Minimize overhead irrigation and avoid splatter from puddled water. If plants are in ground beds, make sure the soil is well drained and not previously contaminated with plant pathogens.