39+ Brown Tomato Plant Leaves. Stress from drought often appears first as browning, drying leaf margins before spreading farther into the plant's tissue. If brown leaves develop on the lower parts of young tomato plants, trim these away and destroy them, using shears that you wipe with rubbing alcohol between cuts to prevent spreading the disease.
It is often referred to as the tomato moth by gardeners as its caterpillars also feed on the fruit and leaves of tomato plants as well as many other herbaceous plants.
So, if you notice your leaves turning brown before they go yellow you should look for a solution as soon as possible. Brown spots on the leaves of your tomato plant can indicate several disease possibilities, generally caused by fungi. The lack of nutrition, particularly this compound, can indicate why the leaves are yellow or brown. Add baking soda to your tomato plants, just days later you won't believe what happens!