39+ Brown Spots On Basil Leaves. Infection usually occurs when water is splashed on the leaves during warm, humid weather or by unsanitary gardening practices, such using dirty gardening tools. I have looked up a lot of information and pictures the mint plants still have lots of healthy looking leaves, but the sweet basil plant has taken a real beating.
Even a short frost can cause the leaf edges and the more vulnerable top leaves to die.
My runoff ph is 5 using ffof soil. Symptoms of infection first show as round brown spots on basil leaves. As these brown spots grow, they become angular blotches. From brown spots to dropping leaves, there are a few common ailments of this plant that can sicken it, or worse, quickly lead to its demise.