Hi,
I was surprise this year. I really have hard time to grow thai basil this year, I tried both germinate from seed (which works last 3-4 years) and move to small pot or even getting the small plant from bigbox store. They all pretty much looks like this in the photo. (leaf spot / gray out, wilt stem the fall down)
I start to suspect this is some kind of disease. Can you tell me what’s the problem and how to solve it?
I do not know what zone you are. But basil like hot weather. We have a cooler spring. It could be just cold damage. No systemic diseases. Haul the pot indoor at night and the plants will recover.
I have (and still do) use Actinovate spray on regular basil. It does a good job of eliminating those brown areas on the leaves. I would think it should work on Thai Basil too.