Septoria Leaf Spot Leaves with gray-brown areas surrounded by a
dark or yellowish margin are one of the early symptoms of this
fungal disease. These discolored areas lack the concentric rings
characteristic of early blight, but they may be filled with many
small, black spores. Symptoms generally appear on lower leaves
first. The fungus can infect a wide variety of plants. In a
severe outbreak, septoria leaf spot fungi may also attack
seedlings. The disease is most problematic in cool, wet weather.
The fungus overwinters on plant debris in the soil and on weeds
such as jimsonweed, horsenettle and nightshade.Prevention and
Control - Plant disease-free seed. - Rotate crops to avoid
growing susceptible plants in the same area year after year. -
Pick off and destroy any infected leaves. - Mulch around the
plants to reduce soil splashing, which can spread the disease. -
Use drip irrigation or soaker hoses rather than overhead
watering. - In the fall, remove any diseased plant material and
destroy it.