The cartoon to the right shows some important phases of the basic life cycle of P. sojae .
Oospores germinate to form zoosporangia .
Zoospores are formed within zoosporangia and then released. Zoospores are biflagellate and chemotactic . Sensing exudates from soybean roots, they swim towards them. Zoosporangia may also be formed directly from mycelium to provide secondary inoculum in epiphytotics.