spinach diseases

Spinach is usually grown for retail in small acreages. Some production occurs in high tunnels or greenhouses. 

Cladosporium leaf spot

Cladosporium leaf spot-lesions are often round. Sporulation may be observed with a 10X hand lens. The outbreak in these photos was in a high tunnel. 
Figure 1. Cladosporium leaf spot of spinach. Figure 1. Cladosporium leaf spot of spinach.
Figure 2. Cladosporium leaf spot of spinach. Figure 2. Cladosporium leaf spot of spinach.
Figure 3. Cladosporium leaf spot of spinach. Figure 3. Cladosporium leaf spot of spinach.

Downy mildew

Downy mildew-not a common disease in Indiana. Look for irregular chlorosis on the top of leaves. Sporulation may be observed on the bottom of lesions under moist conditions. 
Figure 1. Downy mildew of spinach. Figure 1. Downy mildew of spinach.
Figure 2. Downy mildew of spinach. Note sporulation on leaf bottom. Figure 2. Downy mildew of spinach. Note sporulation on leaf bottom.