Botanical Pesticides for Garden Pests

In recent years, due to pesticide legislation, several garden chemicals have been removed from sale and can no longer be used in the garden, house or greenhouse. All pesticides — including botanicals — should be used only as a last resort after thoroughly reading the label on the package.

Although derived from natural sources, botanicals are not necessarily safer or less toxic to non-pest insects, humans, and animals than synthetically derived pesticides. In fact, most botanicals are broad-spectrum insecticides, which kill both good and bad bugs indiscriminately. Some botanicals cause allergic reactions in people, others are highly toxic to fish and animals, and some may even cause cancer.

Most botanicals do not damage plants. Plus, most botanicals and insecticidal soaps are low to moderate in toxicity to mammals, but there are exceptions. For example, both inhalation and skin exposure to nicotine preparations can cause death. Also, rotenone is similar in toxicity to the common synthetic insecticides carbaryl and diazinon.

Common botanical insecticides include pyrethrum and pyrethrins—a dust or extract derived from the pyrethrum daisy. These products are registered for use on animals to control fleas, flies, and mosquitoes. They are also used as indoor household sprays, aerosols, and "bombs." Pyrethrins are sometimes combined with rotenone and ryania or copper for general use in gardens.

The pesticides in this section are listed from least to most toxic to humans.

• Hot pepper wax and powder: The chemical capsaicin causes the heat in hot peppers and it's the active ingredient in these useful botanical products. In low doses, such as found in ready-to-use sprays and dusts, hot pepper wax repels most common insect pests from vegetables and ornamental plants. It doesn't cause the fruit or vegetables to become spicy hot, but instead stays on the surface of the plant where it remains effective for up to three weeks. Stronger commercial formulations kill insects as well as repel them. Hot pepper wax is even reportedly effective in repelling rabbits and tree squirrels.

• Neem: This pesticide is made from the seeds of the tropical neem tree, Azadirachta indica, and it comes in two forms — azadirachtin solution and neem oil. Unlike the other botanical insecticides in this section, neem does not poison insects outright. Instead, when insects eat the active ingredient, it interrupts their ability to develop and grow to their next life stage or lay eggs. It also deters insects from feeding and is effective against aphids, thrips, fungus gnats, caterpillars, beetles, leafminers, and others. Amazingly, plants can absorb neem so that any insects that feed on them may be killed or deterred from feeding.

• Pyrethrins: These insecticidal compounds occur naturally in the flowers of some species of chrysanthemum plants. The toxins penetrate the insects' nervous system, quickly causing paralysis. In high enough doses or in combination with other pesticides, the insects die. Powerful synthetic compounds that imitate the natural chrysanthemum compounds are called pyrethroids. Pyrethroids are not approved for use in organic farms and gardens. Also avoid any pyrethrins that list "piperonyl butoxoid" on the label. This additive is not approved for organic use.

For more related information, check out our site here: