10 dollar bottle of coco wet, and a 10 dollar bottle of Einstein. Follow mixing instructions and bugs wont come back. Its purely organic, but not recommended to use close to harvest.
or you can buy a $40 dollar bottle of azatrol, or any other organic bug repellent that is made for plants.
You can also take 4 cigarettes and boil then in a liter of water. Use this to spray your plants. Nicotine is toxic to all living organisms, even humans, and even your plants. In order for you to kill a human you would need a crap load, but I have tried this and I got some on my fingers one time and I felt very woozy for about 20 minutes. (and I smoke cigarettes...) You would also need a very high dosage to kill your plants, but to kill bugs you need a very low dosage.
This is the cheapest way. (make sure you take off the filter) and boil the cigarettes for at least 10-20 minutes (the longer the more effective it will be). If this does not work the first time, try 5 cigarettes. (but 4 should work fine)