|How can I make pesticides using the following substances: vinegar, sulfur, soap, and/or oil. The insect is a green caterpillar.|
|Insecticidal soap is probably the most effective ingredient against young catapillars in the list you mentioned. It is available from garden centers as a labeled pesticide. Some gardeners make their own using a liquid dish soap like Ivory Liquid at a 1 or 2 percent concentration in water. Avoid spraying soap in the heat of the day and remember that contact with the insect is important if the soap is to be effective. Once dry, soap sprays are no longer effective.
Be advised that to make a homemade concoction is to do so at your own risk (and your plant's). Commercial soap products are specifically formulated to be effective on insects with a minimum of damage to plants.
Another organic option is to purchase a natural pesticide containing B.t. from a local nursery.