Homemade remedies 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, two homemade sprays have proven very effective in controlling aphid infestations. Organic gardeners have been using tomato leaf spray or garlic oil spray to battle aphids for generations.
While knowing how to make and use them is important, it's equally important to understand why they work.
Tomato Leaf Spray
Tomato plants, as members of the nightshade family, contain toxic compounds called alkaloids in their leaves. When the leaves of tomato plants are chopped, they release their alkaloids. When the alkaloids are suspended and diluted with water, they make an easy to use spray that is toxic to aphids, but still safe around plants and humans.
How to Make Tomato Leaf Spray
Simply chop one or two cups of tomato leaves and soak them in two cups of water. Let it steep overnight. Strain out the leaves using cheesecloth or a fine strainer; then add another one to two cups of water to the liquid and add it to a spray bottle.
Applying Tomato Leaf Spray
Use the mixture by spraying the stems and foliage of the infested plant, paying particular attention to the undersides of leaves since that is where aphids most commonly congregate.
One word of caution, while this spray is very safe for humans, some people are allergic to members of the nightshade family. If you are one of them, use care in making and applying this spray.
Garlic Oil Spray
Organic gardeners have long relied on garlic as part of their pest-fighting arsenal. Garlic contains sulfur, which, besides being toxic to pests, is also an antibacterial and antifungal agent.
The dish soap in this mixture also breaks down the bodies of soft-bodied pests, such as aphids.
How to Make Garlic Oil Spray
To make garlic oil spray, mince or finely chop three to four cloves of garlic, and add them to two teaspoons of mineral oil. Let this mixture sit for 24 hours. Strain out the garlic pieces, and add the remaining liquid to one pint of water. Add one teaspoon of liquid dish soap. This mixture can be stored and diluted as needed.
Applying Garlic Oil Spray
Before using this spray 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 won't harm your plant, spray the entire plant, paying particular attention to the undersides of leaves.
A word of caution about this spray, garlic oil is a non-selective insecticide. It will kill beneficial insects (such as ladybugs, who are natural predators of aphids) just as easily as it kills the bad guys. It's best to keep as many beneficial insects around as possible. This spray should only be used if you haven't seen any beneficial bugs in your garden.
The tomato leaf recipe, above, won't harm beneficial bugs, so you should use that if you're lucky enough to have some in your garden.