Tomatoes are every gardener favorite plant. Though it is not always easy to grow perfect tomatoes. Tomatoes have a high risk of diseases and they also attract unwanted pests. As, you mentioned that the older, lower leaves are wilting, generally tomatoes wilt due to over watering; leaves, stem, shoots and fruit die due to over watering. Tomato plants that remain in the water quickly wilt due to extra moisture. You can take help of some professional like
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as you mentioned it is spreading to other plants as well so in order to stop that, you can take the help of a pest control guy or you can do one thing that is; take out the plant from the soil, pour some water over the stem and roots. Then cut the plant at the lower end, this Court must be four inches in length. Now have a jar filled with water and put the stem section in water.