• Identifying and preventing diseases that cause black spot can keep the rest of your pea plants healthy.C Squared Studios/Photodisc/Getty Images
  
  Black spots on pea plants are never a good sign. The fungal and bacterial diseases that cause black spots almost always kill the plant, and the only solution is to pull it out before other plants are infected. There are, however, a few things you can do to identify the disease and prevent it or at least stop it from spreading to your healthy plants.
  
  

Causes

• Three common bacterial and fungal problems can cause black spots on pea plants. Bacterial blight, which causes spots on the stems, pods and leaves, is carried in infected seeds and cannot be cured. Fusarium wilt -- also known as true wilt -- and near wilt are diseases caused by fungi. Plants with fusarium wilt have black discoloration of the water-conducting tissue within their stems, according to the University of Illinois. Those with near wilt will often develop black spots, or cankers, at the base of the stems.
  
  

Bacterial Blight

• Plants with bacterial blight have dark, irregularly shaped spots on their leaves, watery yellow to brown spots on their pods and purple to black spots on the stems near the soil line. As the infection advances, the plants may drop blossoms or young pods, turn brown or die. Because this disease is spread through infected seeds and debris, it is extremely important to destroy problem plants and those surrounding them as soon as the symptoms are discovered. To prevent bacterial blight, use commercially grown disease-free seeds, rotate crops yearly and avoid working in the garden when it is wet.
  
  

Fusarium and Near Wilt

• Fusarium and and near wilt can also devastate a pea crop if not controlled. Plants may become infected with the fungi that cause these diseases at any stage in their growth cycle. Besides the black discoloration, symptoms include yellowing of lower leaves, stunted growth and thickened or brittle stems at the soil line. Both types of fungi are spread through spores in the soil, and once a field is infected it cannot be eradicated.
  
  

Wilt Prevention

• To prevent wilt fungus in your garden, plant only wilt-resistant varieties of peas. Plant as early in the year as possible so plants can get established before the soil reaches the optimum temperature for the fungi -- which starts at 74 degrees F. Also, establish a five-year or longer rotation and promptly remove all debris from your garden. Finally, If you live in a humid area, the University of Illinois discourages saving your seeds.