A pesticide is a chemical formulated to kill an unwanted plant, insect, fungus or animal. There are many names for pesticides including herbicide (kills plants), insecticide (kills insects) and fungicide (kills fungi). Baits are pesticides that kill vertebrate pests (animals).

Pesticides may be derived from either synthetic or organic ingredients, but don’t be fooled by the words “organic” or “natural.” Whether made from synthetic or organic ingredients, both types of pesticides are formulated to kill their intended subject. Some types of pesticides are toxic to humans and beneficial insects. If you want to garden without killing beneficial insects and pollinators, use horticultural oils or soaps which are carefully formulated to be gentler than most pesticides. Always read and follow directions on the label.

Horticultural Oils

Horticultural oils are sometimes referred to as dormant oils because they’re used to kill overwintering pests during plant dormancy (when plants lose their leaves). Pests killed include soft-bodied insects such as aphids and thrips, scale insects and spider mites. Horticultural oils are also used to prevent powdery mildew, a common fungus disease. The plus side of horticultural oils is they leave little residue behind and are virtually non-toxic to bees and most beneficial insects.

Horticultural oils are either plant-based or made from petroleum. Read the directions carefully before use as some plants do not tolerate horticultural oils. Make sure to apply the oil according to the instructions; applying oils during warm weather can harm plants. Read more about Horticultural Oils from Colorado State University.

Insecticidal Soaps

Insecticidal soaps are made from a combination of plant or animal fatty acids and potassium salts. The soaps target soft-bodied insects such as aphids, scale, mites, mealy bugs and thrips. This pesticide also washes away sticky honeydew and sooty mold left behind from the insects’ feeding.

The plus side of insecticidal soaps is they leave little residue behind and are virtually non-toxic to bees and most beneficial insects. If you want to know more about insecticidal soaps in depth, read Insecticidal Soaps for Garden Pest Control by Clemson Cooperative Extension.

Oils and Soaps-Should you make your own?

Horticulturalists recommend gardeners purchase horticultural oils and soaps since “recipes” posted online have not been tested. If you create your own formula you may unintentionally harm the plant you intend to protect, or harm bees and other beneficial insects while adding unneeded chemicals into your soil.

Pests and Beneficial Insects

In spring, many critters hatch all at once and can be a nuisance. Ruined produce or defoliated plants can make any gardener want to pull out a can of “kill them all!” This is a good time to take a deep breath and remember that in nature, there is a balance between pests and predators, and that in order for the beneficial insects to have food, pests must exist.

Weeds & Herbicides

Herbicides are a type of pesticide formulated to kill specific weeds. Not all herbicides kill all weeds, so it’s best to read the label before making a purchase. Also, remember that the words “organic” or “natural” do not necessarily mean they are safe to use around wildlife. Many of these herbicides are toxic to fish, beneficial insects and pollinators. On another note, many “weeds” are larval food plants for butterflies and other insects.

To learn more about pests in your garden read the following articles:

  • Insect Pests
  • Animal Pests
  • Diseases
  • Weeds

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