Will Using Liquid Pesticide Detergent Change the Taste of Vegetables?

Identification

• Insecticidal soaps are detergents -- plant and animal fatty acids combined with a strong akali -- in a formula that is “just right” to kill bugs but not damage plants or other animals unless they get it in their eyes or drink it. Each brand of this liquid detergent-pesticide has its own proprietary formula, but all lack the perfumes and other additives found in dish soaps and laundry detergents. Insecticidal soap serves as a surfactant for several petrochemical-based and organic pesticides.

Function

• Pesticides perform in one of two ways: They can be systemic, meaning they are absorbed into the plant’s system, or they can be contact pesticides, which work only on bugs on the surfaces of plants. Insecticidal soap is a contact pesticide that not only works on the surface but must contact the target insect when wet. The liquid form disrupts the cellular walls of the membranes in soft-bodied insects and acts as a surfactant, dissolving protective waxes on the insect’s outer skin, which leads to dehydration. Bugs must get soaked for insecticidal soaps to work properly.

Effects

• Soaps are ineffective when dry, with a few exceptions such as tomatoes or cucumbers where dried soap may interfere with the plant’s ability to use sunlight in a condition called phytotoxicity. Repeated applications of insecticidal soap may also lead to marking of some fruits’ skins. Soap labels caution against combining insecticidal soap with applications of liquid nitrogen fertilizer on brassica leafy vegetables and recommend rinsing plants after soap has dried to avoid damage. Insecticidal soaps can be applied until harvest and, providing the vegetables are well washed, will not affect their taste.

Considerations

• Other than physical changes in vegetables caused by the decline of plant health resulting from phytotoxicity or heavy, frequent applications of insecticidal soap, taste should not change. Homemade liquid soap mixtures cannot equate to commercially available insecticidal soaps and are likely to either be ineffective or too harsh. Like insecticidal soaps, however, they function on contact. Though they may damage the plant or affect its yield, they will not change the taste of the vegetable unless the food is not washed before consumption.