Tomato – spraying with detergent

Q: My mother had an incredible vegetable garden, with huge tomato plants. However, she had whiteflies all over her plants. My sister-in-law told her of a remedy she had seen on a public television gardening show. She advised to spray the plants with 1 part dishwashing detergent mixed with 5 parts water. Now all the leaves are shrived up and brown. The tomato plants still have green tomatoes on them but the plants look like they are just about dead.

A: Soap has long been used as an insecticide but detergent is an entirely different chemical. Seeing your 1:5 proportion, I can easily see how the plants were burned. A typical insecticidal soap concentration is 1:50.

Even so, I do not recommend that you run out and mix liquid hand soap with water to make an insecticide. Soaps made for washing are different from soaps made for killing insects. My advice is to use only products specifically labeled for insect killing.

Hope your sister-in-law gets out of the doghouse soon!