8 Ways to Kill Aphids on Your Tomato Plants

Key takeaways:
Aphids can cause severe damage to tomato plants, so it’s important to quickly control their population. Pick them off by hand or use water to knock them off the leaves.

Encourage beneficial insects like ladybugs, green lacewings, and hoverflies to naturally control aphids. Plant flowering herbs and wildflowers to attract these insects.

Companion planting with plants like garlic, chives, and marigolds can deter aphids. Reflective aluminum mulches and DIY aluminum foil mulches can also help control aphids.

Have you noticed wilting, yellow leaves, or a sticky residue on your tomato plants? You may have aphids! These micro pests, barely ⅛ of an inch, can multiply quickly and potentially cause severe damage to your tomatoes. Aphids love young tomato plants — especially those with new offshoots. The dense foliage is a perfect home and food source for them.

While aphids are common in gardens, unchecked populations can cause significant damage, so quick and effective control measures are vital to keeping your tomatoes healthy. Discover eight ways to kill aphids on your tomato plants.

1. Pick or Water Them OffWater jet

With more minor infestations, you can gently pick aphids off with your hands. Use gloves or a damp cloth to avoid getting their honeydew (a sticky residue excreted by aphids) on your skin. Do this as often as you’d like — though it’s easiest on infestations you have caught early when they are smaller and more manageable. Afterward, wash your hands thoroughly or wipe off your gloves to prevent the aphids from spreading back onto other plants.

Another simple, non-toxic method to rid your tomato plants of mild infestations is to knock them off using water. With a standard garden hose set to moderate pressure, spray the affected parts of your tomato plants, concentrating on the undersides of the leaves where aphids typically cluster.

The force of the water should be enough to knock the aphids off the plant without harming your tomatoes, and you can repeat this process as much as you’d like (with caution so as not to drown the plant). This also rinses away the honeydew produced by aphids.

However, they may attempt to climb back onto the plants, so picking them off or using water should ideally be combined with other control measures (such as those below) for maximum effectiveness.

2. Encourage Beneficial Insectslady bug looking at aphids

Some insects can be great allies in the battle against aphids. For example, ladybugs, green lacewings, and hoverflies think aphids are delicious, so they play a key role in naturally controlling and reducing aphid populations, reducing the need for harmful chemical pesticides. Not only that, but many beneficial insects like bees and butterflies also aid in pollination, which is crucial for plant reproduction and biodiversity. Inviting them into your garden fosters a healthy ecosystem. Entice them into your garden with flowering herbs and wildflowers such as dill, yarrow, Queen Anne’s lace, marigold, and lavender.

3. Deter Aphids With Plants
Green aphids on a plant

Many plants that attract natural pest controllers also deter aphids — so it’s a 2-in-1 solution! Known as companion planting, this strategy involves growing certain plants alongside your tomatoes known to repel aphids, usually plants with strong odors like garlic, chives, and marigolds.

In addition to companion planting, consider using “trap crops”, like nasturtiums or okra, which are more appealing to aphids than tomatoes. This means you can handle the infestation in a localized area away from your tomatoes, by treating your trap crops using another one of the methods listed or by removing them altogether. This allows you to control aphids proactively and protect your tomato plants.

4. Use Reflective Aluminum Mulches
agriculture mulch sheet in black color

Reflective mulch, or metalized plastic mulch, is made from different materials that reflect sunlight. One typical example is silver metallic plastic mulch, which has a shiny surface that reflects light onto the plant. Although it may not be as durable or long-lasting as commercial products, another popular choice is DIY aluminum mulch.

Cut aluminum foil into 1 to 1½-inch strips or squares and place them around your plants, ensuring the shiny side is facing up. Lightly cover it with organic mulch (like wood chips or straw) to ensure the foil is secure and won’t easily blow away.

The frequency of mulch replacement largely depends on the type of mulch used and local climate conditions. Organic mulches like wood chips or straw break down over time and must be replenished yearly, usually in the spring. Reflective mulches are less prone to decomposition and can last for multiple growing seasons, but should be replaced if they become tarnished or damaged to maintain their effectiveness against pests.

While reflective mulches are a worthwhile aphid control strategy, it’s most effective when combined with other methods, such as companion planting. Reflective mulches also offer additional benefits to your tomato plants, such as enhancing growth by increasing light availability to your plants and helping to regulate the temperature of the soil.

5. Using Baking Soda
Hand holding a gardening shovel with baking soda

Create a spray by mixing ½ teaspoon of baking soda with 2 cups of water, ⅔ cup of olive oil, and four to five drops of mild dish soap to help the mixture adhere to the plant.

The alkalinity of the baking soda solution disrupts the aphids’ natural pH balance and releases carbon dioxide, making it hard for them to breathe. Spraying directly onto the aphids can kill or deter them from feeding on your plants. The solution also helps to combat the mold that often arises from the honeydew they excrete — along with some other benefits!

Monitor the infestation and repeat once weekly until the aphids are gone. Baking soda can also alter the soil’s pH level, which could harm your plants – even causing plant death, so it is crucial to use this method judiciously and monitor your plants closely for any signs of distress such as desiccation sun damage or burning.

6. Create an Oil Spray
spraying fungicide on tomatoes

Oil is an excellent organic compound that suffocates aphids, effectively killing them and preventing future infestations. You can use several kinds of oils, such as petroleum-based horticultural oils, vegetable oil, canola oil, and neem oil, which is antifungal and doesn’t disrupt beneficial insects. You could also use garlic oil since aphids hate the smell of it.

Generally, 1 teaspoon of oil, ¼ gallon of preferably lukewarm water, and ¼ teaspoon of gentle liquid soap should do the trick. Recipes may vary depending on the type of oil you’re using so that you don’t unintentionally harm your plant. Thoroughly spray all the nooks and crannies once a week during infestations. When the infestation is gone, reduce sprayings to once every two weeks as a prevention tactic.

7. Use Diatomaceous Earth
a jar and mini sieve with DE

Diatomaceous earth is a natural, powdery substance with microscopic, razor-sharp edges made from fossilized aquatic organisms known as diatoms. By sprinkling diatomaceous earth on the soil around your tomato plants, you create a protective barrier that can pierce the bodies of small insects like aphids, leading to dehydration and death.

Replenish the powder around your plants after heavy rain or heavy dew to uphold the protective barrier, and keep reapplying until you see a reduction in aphids. Use it cautiously, as it can harm beneficial insects and cause irritation when inhaled.

8. Apply Insecticidal Soaps
Pest Control spraying tomatoes

If the mild dish soap hasn’t worked, try insecticidal soap, which penetrates the aphids’ outer shell, causing them to lose essential body fluids. Remember to spray the underside of leaves and stems where aphids often congregate.

Soap-based sprays are effective in combating aphids only while they’re wet. Therefore, reapplication is necessary every four to seven days or until you observe a noticeable reduction in the aphid population. Rinse away any soap residue afterward.
Eco-Conscious Over Chemical for Aphid-Free Tomato Plants

While chemical pesticides may seem like a quick fix, they often harm pests and beneficial insects and potentially affect your tomatoes’ edibility. Consider the organic methods listed here — from employing beneficial insects to using household items like baking soda and oils — to protect your plants instead.

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