My basil plants (leaves) turn black and die.
I have removed all of the affected leaves but when they grow back, they turn black again. I have used need oil and other sprays but nothing will stop it.
Certified GKH Gardening Expert
It sounds like you are going to have to remove the soil from the area, or container, if possible, and treat for a fungal infection.
During wet seasons, or if overwatered just a little too much, these plants can suffer infections quite easily. Make sure the soil is almost completely dry between watering, as these are quite drought hardy.
I would recommend treating the area, or fresh soil with dolomitic lime and wettable sulfur to help with spot treatment, and prevention for future infection. I give all of my plants these at least once per year for the same reason.
This collection of articles will help: https://www.gardeningknowhow.com/edible/herbs/basil