Many different home remedies have been touted to repel any number of pests on plants. Because ingredients in homemade remedies can vary greatly, it is difficult to know the phytotoxicity of a solution or guarantee plant safety. For this reason, I'll restrict my references to commercially available repellents. If I don't mention a favorite repellent, there is no reason to believe it's ineffective. If you have a good track record with something that is not harming your plant but is deterring pests, you have a useful repellent.
Diligence is key in applying repellents Most repellents are applied to plants as foliar sprays.
In addition to thorough coverage, the secret to getting repellents to work for you is in your application diligence. Most repellents will not persist on plants after rainfall or beyond five to seven days, so multiple applications over time are necessary for protection. The repellents' lack of persistence can also be a good thing because it means that any of their distasteful, bitter properties are also removed from your plants before you harvest them to eat. It is important to apply the compounds before the levels of pest damage are severe because most repellents have a limited ability to reduce high pest populations. Many pests, such as Japanese beetles, have been shown to make plants more attractive to further pest visits once the plant has been fed upon.