Understanding Downy Mildew: A Guide to the Peronosporaceae Family of Fungi

Peronosporaceae is a family of fungi that includes the downy mildews. These are plant pathogens that cause disease on a wide range of host plants, including many crops and ornamental plants. The name "downy mildew" refers to the white, cottony growths that appear on the leaves and stems of infected plants. These growths are actually the fruiting bodies of the fungus, which produce spores that can spread the disease to other plants.

Peronosporaceae is a relatively small family of fungi, with only about 20 genera and around 300 species. However, these fungi are found all over the world and can cause significant damage to crops and gardens. Some of the most common hosts of downy mildews include grapevines, roses, and lettuce.

Peronosporaceae are biotrophic, meaning that they require a living host plant in order to grow and reproduce. The fungus grows inside the plant tissue, using the plant's nutrients for energy and growth. This can cause a range of symptoms on the plant, including yellowing or stunted growth, as well as the characteristic white, downy patches.

Peronosporaceae are often spread through the movement of infected plants or contaminated soil. They can also be spread by wind or water, which allows them to travel long distances and infect new areas. Once a plant is infected, it can be difficult to control the disease, as the fungus can persist in the soil for many years. However, there are some cultural and chemical controls that can help manage downy mildew outbreaks.