According to Ethical Investing:

If you choose to avoid investing in Monsanto, you probably would like to avoid purchasing their products as well. After all, purchases of their products directly funds the destruction of people's health around the world. Fortunately, there are alternatives to all of their harmful products.

Here's a list of Monsanto products to avoid and a list of alternatives.

If we want control of our food production then a big first step is to STOP supporting Monsanto.