Irregular brown spots appear on lower leaves first. Lower leaves fall off, exposing tomatoes to sun, causing sunscald. On old plants, it sometimes causes black, sunken spots near the stem end of fruit.
Start spraying Bacillus subtilis or a copper soap fungicide every 7-10 days soon after setting out plants. Reapply after rain. Apply more frequently if disease is increasing rapidly. We recommend Plant Guardian Biofungicide Wettable Powder and Soap-Shield Flowable Liquid Copper Fungicide. Weed Barrier Mats (Heavy or Medium weight) prevent splashing from soil so blight spreads more slowly.