Just one tomato plant wilted
I have about 40 tomato plants, different varieties, some heirloom, some hybrid, all are planted through landscape fabric (not plastic) against a trellis. Almost all of the plants are doing well, but ONE plant, a variety called Earliana, is suddenly wilted. I noticed it 3 days ago and gave it extra water (just in case) but it's still wilted today. It is between a healthy basil plant and a healthy (other variety) tomato plant. As you can see from the pictures, it stands out in the row of otherwise normal plants. This is the one and only Earliana plant I have, and it is the only one affected. I got down and looked at the stem base and it seems to have a white fungus or other thing growing on the stem ( in the picture, it looks yellowish but in reality it's more white). Should I yank that plant out and throw it away? Is there any way to save it? It's strange that this is the only plant with curled, wilting leaves and drooping stems.
You should definitely remove it, along with the soil there, bag it up and throw it away.
The white portion at the bottom of the stem is a fungal mat of Southern Blight. It is soil borne and could possibly affect other plants.
See here: http://extension.umd.edu/hgic/southern-blight-vegetables
I already pulled it and bagged it in plastic since it had gotten way worse. How much soil must I remove?
Only an inch or two right around the plant. When you replant next season, be sure to add/amend soil with organic matter like compost or aged manure, etc..