I always use the neem oil, because this stuff is 100% organic, cheap, easy to use and really effective agains almost all the bugs that are a threat for our beloved cannabis.
But I tought a link to a website that explains about every single option would be better.
When you want to use neem you need to use an emulsifier aswell. You can use just a little green soap for this. Just spray the leaves with a 3% neem oil and water solution for 5 days in a row and the bugs are gone (it really kills almost all the bugs, but is harmless for the plant!!!). And when you have bugs in the soil like gnats you just give this same 3% neem oil and water solution but then just with watering 3 times in a week and same result. Bugs death, plants and grower happy! š
Happy Growing! š