why is it on just one leaf? look on the bottom of the leaf and if the yellow spot is grayish purple then you have downy mildew. and you have to treat it with a fungicide. like daconill.

if you had alot rainy weather, it is a air borne virus and isnt in the soil.

I sprayed with garden neem last night. After work this afternoon I'll have to check on it. Is that bacteria deadly? It's on a bunch of the plants, hopefully they'll recover. What's everyone's experience with the garden neem on fungus and squash bugs?

I just turned over the leaves... I don't see anything on the undersides... what could it be?

bacterial leaf spot is the only thing i can think of. heres a spray you can use or you can use a fungicide like daconil.
�Mix 1 tbsp of baking soda and 1 tbsp of dormant oil or vegetable oil
�Add 4 liters of water
�Stir well
�Add � tbsp of dish washing liquid soap
�Stir it again