Extension

This week’s article is a continuation of alternatives to synthetic insecticides to control unwanted pests in the garden. The previous article focused on handpicking, exclusion devices, traps and attractants, water pressure sprays and insect vacuums. Here are a few more environmentally friendly options that can help keep pesky insects out of the garden but aren’t harmful to the beneficial insects who may call your garden their home.

 

1. Insecticidal soaps: Just as a bar of bath soap or bottle of shower gel helps keep our bodies clean, insecticidal soaps will help control insect pests by penetrating the insect’s outer coat cuticle or entering the respiratory system and causing cell damage or disruption. Several insecticidal soaps are available to control insects and mites and contain the active ingredient of potassium salt of fatty acids. These soaps sold for insect control will minimize plant injury. Certain brands of hand soaps and liquid dishwashing soaps can be effective alternatives but be cautious because there is an increased risk of plant injury. Don’t use dry dish soaps or clothing detergents as they are too harsh for plants. A drawback to using soap-detergent sprays is their potential to cause phytotoxicity. Certain plants are sensitive to these sprays and can be seriously injured. There is a higher risk of plant injury with homemade sprays using household soap or detergent.
2. Horticulture oils: These oils are petroleum-based products and contain certain fatty acids that form layers on plant parts to smother insects or provide a mechanical barrier to prevent plant damage. There are two types of oils, including growing season and dormant, and should be applied accordingly.
3. Diatomaceous earth: Diatomaceous earth is composed of finely ground skeletons of fossil diatoms (a common type of unicellular phytoplankton). Sharp edges of the ground diatoms scratch the waxy or oily outer layer of soft-bodied insects, which causes them to eventually die from dehydration. Diatomaceous earth is considered a pesticide but is non-toxic to birds and mammals. On the downside, it can kill beneficial insects such as lady bugs. Also, it is less effective against pests in humid weather. It’s important for gardeners to wear a dust mask when applying diatomaceous earth to plants. Keep in mind that the formulation of diatomaceous earth sold for swimming pool filters does not help control insects.
4. Biological control: Gardeners may want to introduce natural predators to the garden, including ladybugs, lacewings or predatory beetles to help control pest populations.

 

All the methods outlined in this column and the previous column have their own strengths and weaknesses. It’s essential for gardeners to choose the most appropriate method based on specific pest problems, environmental factors and the plants involved.