Blight And Septoria Leaf Spot - Tomato
These are foliar diseases that attack tomatoes, and sometimes potatoes.
The fungal pathogen for both the diseases overwinter in infected
crop residues. Early blight is caused by the fungus, Alternaria
solani, and septoria leaf spot is caused by Septoria lycopersici.
They are very common during warm, and humid conditions. Early
blight appears mainly on older leaves at the base of the plant
as yellow spots which later turns into dark brown spots. It can
attack also petioles, stems, and fruits. The attack on the fruit
occurs mainly on the calyx end.
The septoria leaf spot symptoms on leaves first appear as water-soaked
lesions on the lower leaves eventually developing into leaf spots,
which are smaller, and numerous appearing on the upper leaf surfaces.
Commercial growers - rotate tomatoes with other vegetables every
three years. Commercial/home gardeners - plant certified disease-free
seeds or transplants, and plant disease-resistant tomato cultivars.
Improve the fertility of the soil to encourage growth of vigorous
plants. Use regular application of copper and other fungicides
if recommended in your state.