What to Know About Natural Pesticides

Medically Reviewed by Poonam Sachdev on June 28, 2022
Written by Sharlene Tan
4 min read

Many people are turning to natural pesticides as a less toxic, more environmentally friendly alternative to synthetic pesticides. 

Natural pesticides are pesticides that are made from things found in nature. They may be made from minerals, plants, minerals, or microorganisms.

Experts have found that these natural pesticides don’t remain in the environment as long as synthetic pesticides. They’re considered less toxic and more environmentally safe than many synthetic pesticides.

There are several different methods of natural pest control. 

Botanical pesticides. These pesticides use naturally occurring chemicals that are derived or extracted from plants or minerals.

One of these botanical pesticides is neem. This comes from the neem tree: Azadirachta indica. Experts say that neem extract is toxic to caterpillars, aphids, and termites. It has low toxicity to mammals, though, and is biodegradable.

Pyrethrins are a mixture of six plant chemicals used to control pests like fleas, flies, moths, and mosquitoes. It’s a compound found in some chrysanthemum flowers. It can be found in over 2,000 registered pesticide products. It’s fast-acting and is low in toxicity to mammals.

Biochemical pesticides. While conventional pesticides neutralize pests, biochemical pesticides have substances like plant hormones that may interfere with mating and other behaviors. Some may produce plant extracts that attract insects to traps.

Microbial pesticides. This type of natural pesticide has a microorganism as its active ingredient. Microorganisms include fungus, viruses, and bacteria. Microbial pesticides can control different types of pests.

The most common microbial pesticides are strains of Bacillus thuringiensis (Bt). The different strains kill a few specific species of larvae. For example, some Bt ingredients are meant to control larvae of mosquitoes and flies, while others target moth larvae.

You can make some natural pesticides at home. Be very careful when using these homemade pesticides, though, as their toxicity, environmental effects, and effectiveness at deterring pests haven’t been fully studied by researchers.

Here are some examples of homemade pesticides:

Soap spray. You can use liquid dish detergent or certain hand soaps to make soap solution. Don’t use dry dish soaps or laundry detergents, though. Use 2 tablespoons of grated soap in 1.5 liters of water. Apply directly on the insects. This may help kill aphids, caterpillars, white flies, and more. Soap spray may harm some plants, though, so test a small area on the plant and wait 24 hours to see if there are any effects. 

Mint repellent. You can use fresh mint leaves and orange or lemon peels to make a repellent against cabbage pests, flea beetles, and aphids. Place the mint leaves, peels, and water in a pan. Bring to a boil. Leave to soak overnight. Apply in the evening. 

Hot pepper repellent. This may be useful against different pests like beetles, ants, caterpillars, and cabbage worms. Finely chop 15 peppers and place them in 1 liter of water. Leave to steep for 24 hours. Strain before using. 

Garlic brew. You can use this garlic solution against insects like ants, caterpillars, and aphids. It may also work against nematodes. Chop ½ cup of garlic finely. Add it to ¾ liters of water and leave it for 24 hours. 

Grow some plants. Another way of repelling insects naturally is to plant certain species of plants in your garden. These include:

  • Rosemary. This repels many different insects, such as cabbage moths, mosquitoes, and flies.
  • Marigolds. Many garden pests like squash bugs, slugs, and tomato hornworms keep away from marigold plants.
  • Chrysanthemums. Many insects stay away from this flowering plant. These include ticks, spider mites, and Japanese beetles. 
  • Lavender. This strongly scented plant puts off mosquitoes, as well as deer and mice, though pollinators like bees love it.
  • Basil. This herb is often used on farms and gardens to keep pests away from more vulnerable crops and flowers. 

They may be less toxic than synthetic pesticides, but natural pesticides are not necessarily safe. Care must still be taken around natural pesticides, as they are meant to kill insects.

Check the labels of your pesticides, whether natural or synthetic. The labels should indicate the toxicity of the pesticide.

Many insects and diseases in your home garden can be resolved by removing the pests by hand or clipping the diseased plant parts. If this fails, pick the least toxic and most effective pesticide. Always read and follow the pesticide instructions.

Toxicity to animals. Some natural pesticides may be nontoxic or mildly toxic to people, but they may be very toxic to some animals. For example, the natural pesticide ryania, which comes from a plant, is toxic to fish.

May be harmful to bees. While many insects are harmful to plants, there are also plenty of useful insects. Bees, butterflies, and other insects pollinate plants. An estimated 80% of flowering plants depend on insects for pollination.

In a study of different natural insecticides, researchers found that many were toxic to honey bees. The natural insecticides tested include:

Some of these natural insecticides, such as neem oil and garlic extract, have been described as “safe” for honey bees. However, this scientific study found that even these “safe” pesticides reduced the number of larvae in bee colonies, and resulted in deformed larvae.

Researchers also found that natural pesticides may affect honey bees’ pollen foraging behavior. One study indicated that worker bees visited syrups that had natural pesticides less than syrups containing only sugar and water.

If possible, try not to spray natural pesticides on flowers directly. If you have to spray flowers, apply pesticides only in the evening, when bees are not foraging. Honey bees tend to forage when the temperatures are above 55 to 60 degrees Fahrenheit (13 to 15 degrees Celsius). When the sun sets, they return to their hives. When you spray pesticides in the evening, this reduces honey bee deaths.