I am new to gardening and juyst started 6 months back. I live in South Floria. I planted a Thai basil plant sometime back and it was growing fine until a 3 months back when I noticed light brown spots on the plant. Also the leaves at the top of the branches are shrinking and I noticed this black tiny insects on it. I tried spraying some organic pesticide on it once every few days, but it does not go away. Please help me save my basil plant.
My Thai Basil has brown spots on all the leaves
I'm not sure what caused the spots unless you sprayed them with something right before they showed up. Even if just plain ol' water gets on basil leaves, direct sunlight can cause burn spots like that. From the second picture it looks like you have foliar thrips. The bad thing about them is that they can fly/jump so when you spray they just leave the plant and return later. But if you can keep at them with the spray you're using you might at least put a dent in their populations.
I have not kept them in direct sunlight, so not sure why the brown spots still appear.
Try this thread and see if anything looks like what you have. http://www.extento.hawaii.edu/kbase/reports/Herbs/basil.htm