If you delight in gardening and have a few plants, veggies or fruits in your landscape, chances are you've probably noticed a leaf-eating, sap-sucking or fruit-boring pest once or twice. Homemade insecticides are generally safe and many times OK for organic gardens. Some will keep insects and bees away, others will kill the pests. Keep in mind, however, that most vegetables and fruits, and many ornamental plants rely on bees for pollination.
Several common ingredients are mentioned in old wives' tales and more recently tested recipes for homemade garden insect repellent. Many homemade repellents include a dishwashing soap or other type of household soap, and cooking oil. Garlic, basil, cayenne pepper, and other plants and common food items are sometimes used, as well. In some cases, the efficiency of the products have been lab-tested, and either proven effective or shown mixed results.
Application and Mixing
A tea or mixture is made from the ingredients, often requiring boiling or steeping to release oils and make a more usable spray. In most cases, homemade liquid repellents require frequent applications. Spraying on a day with calm winds and no chance of rain is ideal as the mixture will have a better chance of staying on the plants. When dish soap or cooking oil is used, pest insects are suffocated, but direct contact is required for efficacy. Garlic, onions and cayenne pepper are repellents, discouraging pests to move along.
Products containing oils or soaps control soft-bodied pests such as aphids, mites and mealybugs. These pests don't have thick cuticles covering their bodies, meaning the soap effectively blocks respiration. Garlic, cayenne pepper, onion and similar products have repellent tendencies, either taste, smell or by touch, that are repulsive to pests.
Soap- or oil-based products can damage many plants, particularly hairy plants or those with waxy-leaves. The soap and oil can quickly diminish the waxy coating. Cruciferous plants are among those damaged. Before applying any homemade insecticide, test a small section of your plant to make sure the plant's outer coating isn't damaged. Oils and soaps, while effective at suffocating many pests, can also damage certain beneficial insects as well. Some recipes you may come across may call for fuel oils or harsh cleaning chemicals; these products are often dangerous to plants, animals and humans, and should never be used.