Homemade remedies for pesky insects are a longstanding tradition among organic gardeners, who have had to be creative in finding ways to battle insects and diseases without the help of synthetic chemicals. In the case of fighting aphids, or plant lice, two homemade sprays have proven very effective: tomato leaf spray or garlic oil spray. While knowing how to make and use them is important, it's equally important to understand why they work.
Click Play to Learn How to Make a Homemade Spray for Aphids
Equipment / Tools
- Bowl or bucket
- Strainer or cheesecloth
- Spray bottle
- Glass or plastic jar with lid
- Measuring spoons
- Fresh tomato leaves
- Garlic cloves
- Mineral oil
- Dishwashing liquid
Tomato Leaf Spray
Tomato plants, members of the nightshade family, contain toxic compounds called alkaloids in their leaves. When the leaves of tomato plants are chopped, the alkaloids are released. By suspending the alkaloids in water, they make an easy-to-use spray that is toxic to aphids, but still safe around plants and humans.
Chop and Soak Leaves
To make tomato leaf spray, simply chop enough tomato leaves to make one or two cups and combine with two cups of water in a large bowl or bucket. Let the solution steep overnight.
Strain and Place in Spray Bottle
Strain out the leaves using cheesecloth or a fine strainer. Add an additional cup of water and pour into a spray bottle. Be sure to label the bottle.
To use the mixture, spray the stems and foliage of the infested plant and pay particular attention to the undersides of leaves since that is where aphids most commonly congregate.
Garlic Oil Spray
Organic gardeners have long relied on garlic as part of their pest-fighting arsenal. Garlic contains sulfur, which, besides being harmful to pests, is also an antibacterial and antifungal agent. The dish soap in this mixture also breaks down the bodies of soft-bodied pests like aphids.
Chop and Steep Garlic
To make garlic oil spray, finely chop three to four cloves of garlic. Place in a small bowl, and add two teaspoons of mineral oil. Let this mixture sit for 24 hours.
Strain and Place in Container
Pour two cups of water into a glass or plastic bottle. Use a strainer to remove the garlic pieces and add the remaining liquid to the water. Add one teaspoon of dishwashing liquid. Label the container.
This mixture can be stored and diluted as needed. Add to a spray bottle before using.
Before using this spray on the entire plant, test it by spraying an inconspicuous part of the plant. If there are no signs of yellowing or other leaf damage after a day or two, it is safe to use. If there is leaf damage, dilute the mixture with more water and try the test again. Once you have determined that it will not harm your plant, spray the entire plant, paying particular attention to the undersides of leaves.
Garlic oil can be harmful to beneficial insects such as ladybugs, which are natural predators of aphids. It is best to keep as many beneficial insects around as possible. This spray should only be used if you have not seen any beneficial bugs in your garden. Otherwise, you should use the tomato leaf recipe, which will not harm beneficial bugs.
Other Natural Methods
- Try to attract beneficial insects like ladybugs, lacewings, parasitic wasps, or damsel bugs to your garden with plant selections. They will attack the aphids. Plant mint, fennel, dill, yarrow, and dandelions to attract these beneficial predators to your garden.
- Avoid over-fertilizing in the garden. Too much nitrogen encourages lots of new, tender growth that aphids love.
- Cut an aluminum pie plate to fit around the base of the plant. The reflected ultraviolet rays from the sun's light cause the aphids to move away from the plant.
Integrated Pest Management for Aphids. Clemson University Extension Service.
Pomilio, Alicia B., et al. Toxic Chemical Compounds of the Solanaceae. Natural Product Communications, 2008, doi:10.1177/1934578X0800300420
“A Review of Bioinsecticidal Activity of Solanaceae Alkaloids.” Toxins 8, no. 3 (March 1, 2016): 60. https://doi.org/10.3390/toxins8030060.
Omar, SH., Al-Wabel, NA. Organosulfur Compounds and Possible Mechanism of Garlic in Cancer. Saudi Pharmaceutical Journal, 18,1,51-58, 2010, doi:10.1016/j.jsps.2009.12.007
Almanac, Old Farmer’s. “Aphids.” Accessed August 17, 2021. https://www.almanac.com/pest/aphids.
Encouraging Beneficial Insects in Your Garden. Oregon State University.
Reflective Mulches Foil Insects. University of California, Agriculture and Natural Resources.