Brown Spots on the Stems of Basil Plants

Colletotrichum Leaf Spot

• Colletotrichum leaf spot of basil is a fungal disease that infects the foliage and stems. Symptoms of the disease first appear as dark spots on leaf surfaces, leaf tissue death that creates a shot-hole appearance and leaf drop. As the disease progresses, it moves from the leaves to the stem of the plant, causing dark stem lesions. Severe infections cause tip dieback and plant death. The fungus spreads by splashing water from diseased plants, and favors moisture on leaf surfaces and high levels of humidity. Avoid overhead irrigation and provide adequate spacing between plants for good air circulation to prevent infection. Remove diseased foliage and sterilize planting equipment to prevent the spread of infection.

Cornyespora cassiicola Leaf Spot

• Cornyespora leaf spot is a fungal infection that infects foliage and spreads to stem of the plant, causing spotting. Symptoms begin as small leaf spots that range from gray to black in color. Severe infections cause defoliation and reduced plant vigor. As the disease progresses, it creates browns spots on the stem of the plant. Remove infected foliage and avoid overhead irrigation to prevent and reduce the severity of infection.

Bacterial Leaf Spot

• Bacterial leaf spot is a serious disease that infects the leaves and stems. The disease causes dark spots on leaf surfaces that have a water soaked appearance, spots on stem surfaces and stem rot. The bacterium favors wet and humid weather conditions, moisture on leaf surfaces and splashing water for infection. The disease can also transmit through infected seeds. Avoid overhead irrigation and water buildup on leaf surfaces to avoid infections. Sterilize gardening equipment to avoid the spread of the disease to healthy plants. Remove infected leaves and plants to stop the spread of the disease.

Fusarium Wilt

• Fusarium wilt is a soilborne fungal disease of basil that can cause severe crop loss. Symptoms of Fusarium wilt consist of plant wilt, brown spots on stems, leaf drop and crooked stem growth. The disease can transmit through infected seeds, which can cause new and perennial infections. Plant Fusarium wilt resistant basil varieties to prevent infection. Once infection occurs, avoid planting susceptible basil in the same soil for 8 to 12 years until the disease is no longer present.