Yellowing then brown spots on basil leaves? (!)

last month
last modified: last month

I grew many basil plants of various types this season. During the horrible heat wave we had here in New York just before Ida I noticed the surface of the leaves of some of my basil plants yellowing. I thought the sun was scorching them and gave them more water. Later I thought the leaves never wilted so it could not be a lack of water. Soon they developed black or dark spots in the yellowing regions and started to wither and die. And this continued to get worse and worse even after the rain, when temperatures had dropped significantly.

I looked up some images and maybe the plants got downy mildew or fusarium wilt or both?

The articles mention that sweet basils are most vulnerable. Thai basils and spice basils such as lemon, cinnamon and then purple basil are more resistant. My sweet basil definitely got it first but my Thai basils and Siam Queen basil got it too. The purple basils did not get or have not yet been infected. I was kind of waiting for them to recover or thinking the stress from the heat is making them die sooner, just avoiding considering that their may be an infection. Because I did not want to throw out all those beautiful plants. Finally I took out all the plants that looked infected. Which is most of them.

Maybe you might comment what this is or could be? I have a few pictures from the earlier stages but not the later stage when the leaves were shriveling and dying:

on sweet genovese:

Thai basil:

Starting on Mrs Burns Lemon Basil:

Any idea what this is? What happens now? Will I be able to grow basil next year? I have been growing basil, mint and cilantro in the same area of my garden. Will the other herbs get infected too?

Also, do I have to throw out the soil in the pots where the basil were growing?

Thanks so much!

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