SEPTORIA LEAF SPOT OF TOMATO
Septoria leaf spot is caused by the fungus Septoria lycopersici. Septoria can affect many parts of tomato plants, commonly causing leaf spots and stem lesions. The fungus can survive winter on diseased plant debris or on perennial weeds such as nightshade. In the spring, the fungus produces spores that are windblown or rain-splashed to healthy tomato leaves, causing primary infections.
Symptoms usually begin to appear on the lower leaves after fruit set. Initially round, yellow spots develop. Later, these spots enlarge and turn brown to gray. Tiny black fruiting bodies (pycnidia) eventually form in the center of the leaf spots. These pycnidia produce spores which cause secondary infections, usually in an upward direction, throughout the plant. Heavily infected leaves turn yellow, then brown and fall from the plant. Exposed fruit, due to defoliation, may be damaged by overexposure to the sun (sunscald).
Fungicide applications may be necessary during rainy seasons. Read the label carefully and apply only as directed. Fungicides currently labeled for use are:
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