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Aphids are tiny pest insects that most gardeners have had to address at one time or another. There are over 4,000 different aphid species and their color can range from green to white to black.
Aphids suck the sap from plants, namely, young growth. However, minor infestations usually don’t create a lot of damage. Aphids are capable of rapid asexual reproduction, though, that can turn minor infestations into major ones in a matter of days.
Heavy aphid infestations will cause plant leaves to yellow, wilt, and eventually effect overall plant health.
In addition to the damage they create by eating the sap from healthy plants, they excrete a sticky substance called honeydew. This honeydew attracts mold and ants, which do additional damage to the already-weakened plants.
The good news is, there are a number of natural, organic ways to prevent and treat aphid infestations.
1. Manual Removal
If your aphid problem is on the smaller side, you can simply go out to your garden once a day and manually remove any aphids you see, paying special attention to the underside of the leaves.
If an infestation has already gotten out of control, it may be easier to snip off the effected leaves, or cull the entire plant and dispose of it well away from your garden.
If your plants are more mature, you can spray them with the hose which will knock the aphids off and hopefully drown them.
2. Soap and Water
Dilute a few tablespoons of dish soap in a small bucket of lukewarm water. Using a sponge, or a spray bottle, apply diluted soap water to the plants effected by the aphids.
The soap dissolves the waxy protective coating from the aphids’ bodies, dehydrating them and eventually kill them.
NOTE: This will also kill off and repel beneficial insects, so use with caution.
3. Neem Oil
Neem oil works in the same way as the soap, however it is organic. Dilute a few tablespoons in a few cups of water and spray on the effected plants. Neem oil has the added advantage of repelling other garden pests such as mealy bugs, cabbage worms, ants and caterpillars. It also prevents the spread of many types of fungus on your plants.
4. Essential Oils
Blend together equal parts (4 or 5 drops) of thyme, peppermint, clove and rosemary essential oils. Dilute in a small spray bottle filled with water. This not only kills an active infestation is help repel future generations of aphids. It can also be used on yourself as an all-purpose bug repellent.
5. Attract Beneficial Insects
One of the most natural ways to deter aphid and other pest insect infestations is to introduce or attract beneficial insects to your garden. Ladybugs (lady beetles), lacewing eggs and praying mantises can be purchased online and released into your garden.
If you don’t want to purchase your beneficial insects, you can attract them to your garden with companion plants that they enjoy. See my post on companion plants for a list of the plants that attract beneficial insects.
6. Attract Predatory Birds
Smaller birds will often snack on aphids. Create a welcoming environment for wrens, chickadees and titmice by building houses for them, putting out a water bath and bird feed specific to wrens and chickadees.
7. Dust Plants With Diatomaceous Earth
If you know you’ll have a few days of sunshine, try dusting your plants, especially underneath the leaves, with food-grade Diatomaceous Earth.
There are two theories about why this works. One is that, microscopically, Diatomaceous Earth is very sharp and will physically scratch the protective exoskeleton of insects. The other theory is that, because it is so fine and dry, it sticks to them and dehydrates them. Others believe it’s a combination of both.
The good thing about using Diatomaceous Earth is that it’s completely natural. It’s made up of the fossilized remains of marine phytoplankton. It’s completely safe for humans and mammals (dogs, cats, etc) to eat and has no negative side effects.
Spray the plants first with water. This will knock some of the aphids off and will help the Diatomaceous Earth stick to the plant.
Make sure to sprinkle some around the base of your plants to repel future aphids and other pest insects.
8. Homemade Garlic Spray
Garlic is a potent antibacterial and antifungal agent, and is a natural pest repellent.
Combine three or four cloves of minced garlic and two teaspoons of grain alcohol. Let steep for at least 24 hours. Strain out the solids and pour the liquid into a spray bottle. Mix two tablespoons of garlic liquid to one pint of water.
Note: this garlic spray will also harm and repel beneficial insects.
9. Homemade Tomato Leaf Spray
This is used much in the same way as the garlic spray, however it won’t harm benficial insects. Tomatoes are part of the nightshade family, which means their leaves contain toxic compounds called alkaloids. These alkaloids are toxic to aphids, but safe to use around plants and other animals.
Chop up a cup or two of tomato leaves and add them to two cups of water. Let this mixture steep overnight. Strain the leaves from the liquid and add the liquid to a spray bottle.
Note: if you’re allergic to plants in the nightshade family, use this spray with caution.