Gardeners worried about the safety of synthetic pest-control products sometimes turn to botanically derived compounds instead. But many of those also contain toxic ingredients, such as rotenone and pyrethrins.
“Botanically derived pesticides are not always safe and some are more hazardous than synthetics,” said Linda Chalker-Scott, an extension horticulturist at Washington State University. “Any improperly used pesticide will contaminate nearby terrestrial and aquatic systems.”
And home remedies could be “illegal and possibly fatal to many good things in your garden,” she said.
Instead, consider the benign-neglect school of pest-control – a mix of prevention (such as maintaining healthy soil) and natural controls (such as insect-eating insects).
“I don’t add fertilizers. I don’t use pesticides. I use a wood chip mulch, which provides habitat for beneficial insects like ground beetles that may eat slugs and slug eggs,” Chalker-Scott said in an email.
Ninety-nine percent of the insects in our yards are benign or even beneficial, writes Jessica Walliser in “Attracting Beneficial Bugs to Your Garden: A Natural Approach to Pest Control” (Timber Press). She recommends introducing insects that eat other insects.
“A single ladybug – probably the most illustrious beneficial predatory insect – can consume up to 5,000 aphids during its lifetime,” Walliser said, adding that thousands of other insect species are capable of doing the same thing.
To keep these predatory insects around, however, you have to offer a diverse and pesticide-free garden with plenty of plant-based foods.
“Just like people, most species of beneficial insects need a balance of carbohydrates and protein in order to survive,” Walliser said.
Provide plants that produce flowers with exposed nectaries, she said. “Many beneficial insects are very small and don’t have specialized mouth parts for accessing nectar from tubular flowers. Members of the carrot family and the aster family are great places to start.”
Where to find beneficial insects? Aside from luring them into your yard with the necessary food, water and shelter, you can buy several hundred in containers at garden centers or online.
“Be sure you have everything they need to survive, then look at the types of pests you have in the garden,” Walliser said. “If whiteflies are problematic on your tomatoes, then larval lacewings may be your answer. If aphids are plaguing your lettuce crop, ladybugs may be a better choice.”