[1] It has been considered for a long time to cause downy mildew of a variety of species within the Brassicaceae, on which the disease can cause economically important damage by killing seedlings or affecting the quality of produce intended for freezing.

[4] In warmer conditions when it gets to about 47–53 degrees F the oospores will germinate and produce an appressorium or form a short germ tube.

The mycelium grows intracellularly and haustoria penetrate through the host cells when the temperature is around 60 degrees F. After about 1–2 weeks when the temperature is between 60 and 64 degrees F, conidiophores (the asexual stage) will form out of the plant stomata bearing conidia.

[4] Hyaloperonospora parasitica is an obligate biotroph, meaning it lives off a host obtaining nutrients.

This hypha grows from bottom of the appressorium and works its way through an intercellular junction of two epidermal cells.

[4] The oomycete grows until it has penetrated through the entire leaf where conidiophores are then grown out of the stomata and disseminated by wind and rain.