Another quite effective poison for rats that we can use is the poison based on castor oil. For this we only have to mix a tablespoon of castor oil and a tablespoon of cornstarch or cornmeal in 1 cup of water. We must dissolve these ingredients very well until we create a fairly liquid mixture. It is important that this oil is natural since depending on the quality of this oil, the effectiveness of this rat poison will be prompt. In fact, it is even convenient that this oil is old, but any castor oil is good. It is also advisable to add the juice of one lemon to this mixture . The lemon is a fruit of alkaline nature, the acid of these fruits can hinder the organism of the rats once they have ingested it, this in combination with the previous ingredients can be a lethal poison for these animals. We can put this in a spray and spray it where we think the rats are and this will prevent the rats from returning to that place. We can also add a little more cornstarch and reduce the water to create a paste. We will create several balls with this paste and place them where rats tend to be inside your home.