Immediately remove all affected leaves to get rid of as many spores as possible.
Prune any leafy parts of the plant to improve circulation through the plant
Avoid getting water on the leaves or laying on top of each other – you want to avoid moisture
Make sure to keep the ground under your plant clean. Rake away all leaves and vegetation. Adding mulch can also help prevent spores from spreading.
Keep plants healthy, sicks plants are much more susceptible to leaf septoria than healthy plants
One way to help prevent this fungus from attacking your plants is to rotate crop sites or move to a new location every year.
A copper based fungicide or Biofungicide may be effective at stopping the fungus from spreading though they are best used as a preventative.
Depending on exactly what’s causing your leaf spot, Neem Oil.
NOTE: These fungus spores may stay in the soil over the winter, and attack your plants in the summer. Spores are also easily spread by wind and rain.