Tobacco Juice Kills Bugs, But Beware....

Sarah Ford of Oxford shows off her bouganvillia. Earlier this spring, she accidentally damaged several of her flowering and vegetable plants by experimenting with a natural insecticide. Thankfully, most have recovered.

Backyard gardener Sarah Ford of Oxford recently boiled tobacco leaves, strained them and mixed the resulting liquid with Epsom Salt, dishwashing detergent, and water. She poured the brew into a bottle and sprayed it as a natural insecticide on her tomato and cucumber plants and flowers. The recipe, which she got from a television program, repelled insects just as it should, but it almost killed her plants.

“Thankfully the rains in early July washed most of it off,” she said. Her plants recovered about two weeks after being sprayed.

Mrs. Ford, like many backyard gardeners, normally uses the trial and error method of gardening, but even Dr. Mijitaba Hamissou, a Jacksonville State University biologist who specializes in stress on plants, sometimes struggles with his plants, too. Early this spring, when someone gave him four angel trumpet plants, he planted them in his lab up to a certain stage and then set them out. Insects sheared off two of them almost overnight.

“I used a commercial spray on the other two,” he said.

When using commercial sprays, he said, gardeners should follow directions on the label. Another common sense guide for gardeners who experiment with making their own natural insecticide is test it on one or two leaves of various plants. Even natural plants that are insecticides, such as tobacco, garlic, and chysanthemums, affect each plant they are used on differently.

Hamissou also said that insecticides are often overused because gardeners do not realize that plants provide their own repellent. To understand when to apply insecticides, one must understand the growth cycle of the plant. An immature plant might be susceptible to being eaten by insects at some phases of the cycle, but when it matures, it often produces a natural repellent. The best way to determine when to use insecticides is by frequent observation.

“Plants and insects have been living together for a long time,” said Hamissou. “Insects rely on plants for shelter, and plants rely on insects for pollination.”

Another tip Hamissou offered is to buy biologically engineered plants that repel insects. Scientists have isolated genes from plants that naturally repel insects and introduced them into the cell structure of other plants. Until recently, only corn, tomatoes, potatoes, and other food plants were engineered to resist insects, but a few companies are beginning to offer yard and house plants that resist insects.

Mrs. Ford is now enjoying her ripe grape tomatoes and cucumbers. “I’m not sure I followed the directions off the television exactly,” she said, “but in the future I’ll be more careful about spraying something untested over all my plants.”

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