''Podosphaera fuliginea'' (also known as ''Podosphaera xanthii'') is a

plant pathogen Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomy ...

that causes

powdery mildew Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of ascomycete fungi in the order Erysiphales. Powdery mildew is one of the easier plant diseases to identify, a ...

cucurbits The Cucurbitaceae, also called cucurbits or the gourd family, are a plant family consisting of about 965 species in around 95 genera, of which the most important to humans are: *''Cucurbita'' – squash, pumpkin, zucchini, some gourds *'' Lagena ...

. ''Podosphaera fuliginea'' and ''

Erysiphe cichoracearum ''Erysiphe cichoracearum'' is a fungal plant pathogen that causes powdery mildew disease of cucurbits, including melon, cucumber, pumpkin, and squash. The primary symptoms are white, powder-like spots on the leaves and stems. ''Sphaerotheca fu ...

'' are the two most commonly recorded fungi causing cucurbit powdery mildew. In the past, ''Erysiphe cichoracearum'' was considered to be the primary causal organism throughout most of the world. Today, ''Podosphaera fuliginea'' is more commonly reported.

Signs and symptoms

Powdery mildew is manifest on the plant by white powdery fungal growth on the surface of the leaf, usually both sides of the leaf show fungal growth.McGrath, M.T., 1997. Powdery Mildew of Cucurbits. http://vegetablemdonline.ppath.cornell.edu/factsheets/Cucurbits_PM.htm The host tissue is frequently stunted, distorted, discolored, and scarred. The fruit of infected plants are usually smaller and the flavor is affected negatively, as fewer sugars and solids are stored in the fruit.

Disease cycle

''Podosphaera fuliginea'' uses haustoria to gain access to the leaf epidermal cells. The fungus is usually spread during the spring through mycelium from infected plant, or through ascocarps. Signs appear after 3–7 days of infection if conditions are favorable. The mycelium grows rapidly during the warm summer months with an optimum temperature of about 10-32°C (50-90 degrees F). The leaves are most susceptible 16–23 days after unfolding.Cheah, L.H., et al. 1996. Epidemiology of Powdery Mildew (Sphaerotheca fuliginea) of Squash. http://www.nzpps.org/journal/49/nzpp_491470.pdf High humidity favors the development of disease, but infection can occur at relative humidity as low a 50%. The conidia of the fungus are spread through the air and thus can travel over great distances.Webster, J., Weber, R.W.S., 2007. Introduction to Fungi 3rd Edition. Cambridge University Press. 401-413 The mycelium can also overwinter in the buds of infected plants.

Control

The most common way to control the spread of ''Podosphaera fuliginea'' is with the use of fungicides. Usually sulphur or demethylation inhibitor fungicides are applied. Fungicides are usually applied once a week. Plants should also be kept physically separated to control spread because older plants can be a source of conidia. Fungicide application is not sufficient if the plant's

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...

nutrition is insufficient, and added silicon may protect almost entirely without need for other methods.

References

{{Taxonbar, from=Q7576577 Fungal plant pathogens and diseases Vegetable diseases fuliginea Fungi described in 1832