Sphaerotheca fuliginea is a plant pathogen that causes powdery mildew

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 fungi in the order Erysiphales. It is one of the easier diseases to spot, as its symptoms are quite distinctive. Infected plants display white powdery spots on the...

 on cucurbits. Sphaerotheca fuliginea and Erysiphe cichoracearum

Erysiphe cichoracearum

Erysiphe cichoracearum is a 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 fuliginea causes a similar looking powdery mildew of cucurbits.-...

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, Sphaerotheca 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. 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

Sphaerotheca 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 50-90 degrees F . The leaves are most susceptible 16-23 days after unfolding . 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. The mycelium can also overwinter in the buds of infected plants.

Control

The most common way to control the spread of Sphaerotheca 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.

External links

• Index Fungorum
• USDA ARS Fungal Database