Aphids on Tomato Plants – How to Stop an Infestation

Coming across an unforeseen aphid infestation can be shocking and worrying. I deal with these sneaky pests every year, both on tomatoes and peppers. Each year, I seem to get a bit better at being one step ahead of aphids.

So, in this article, I’d like to share my best methods for dealing with aphids on tomato plants. They can be stealthy, but if you follow these techniques, your aphid problem should reduce dramatically.

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Aphid on tomato leaf underside
Aphid under tomato leaf.

Detect Them Early

The best way to deal with an aphid infestation is to detect it early. Aphids typically make an early appearance, just as the warm weather is arriving in spring.

There are thousands of aphid species, but the most commonly found on tomatoes are green, white, or black aphids. In early spring, winged forms fly to find a suitable plant for reproduction. There, they will give live-birth to many more aphids that will each reproduce very quickly.

Since aphids multiply so rapidly, the problem can get out of hand quickly. By looking over your plants early on to detect their presence, you can prevent an infestation by stopping them while there are few to deal with.

Tips for aphid detection:

  • Inspect closely under leaves
  • Look at young foliage
  • Use yellow sticky traps
  • Look for warped or misshapen leaves
  • Look along stems and on flower buds
Aphids underneath tomato leaf
Aphids underneath tomato leaf.

Once you find an aphid, it has to go! The quickest method I use for a small amount of aphids is to simply squash them with your fingers. It may seem gross, but these bugs don’t bite and are not fast enough to evade you. Wear gloves if you prefer.

Be careful not to damage any of the foliage while you squish the aphids. Also, aphids don’t typically have a very good grip on your plants, allowing them to drop off easily. If this happens, the fallen aphids will surely find their way back onto your plant via the main stem.

For this reason, I always move slowly and avoid tapping or shaking the leaves too vigorously. When aphids fall, they become difficult to find and can continue to inhabit your tomato plants.

The ‘squash it’ method only really works if you catch the aphids early and continually monitor your plants (once a day minimum). If you already have a large infestation, there are some highly effective techniques for getting rid of aphids on tomatoes.


Spray With Water

When the problem seems to be out of control, the first method you should try is to simply spray the aphids off of your plant with water. As I said before, aphids don’t have strong grips, allowing them to fall easily.

For small plants (~12″ or less), you can bring the plants under your kitchen sink. Use the spray nozzle to spray all of the leaves, top and bottom. Allow the water to flow into your drain so all of the dropping aphids can’t survive.

This method is incredibly effective, but only if you cover all of the leaves – it is very important to be thorough! Again, aphids can reproduce at an alarming rate, so leaving even just a few aphids will lead to a new infestation in just a few days.

For larger plants that can’t be brought indoors, you’ll need a hose or other spraying device. The water stream needs to be fairly strong, so a garden hose is ideal. They even make a special hose attachment for getting rid of bugs.

Tip: If your plants are in containers, bring them to another location before spraying. This way, the fallen bugs will be less likely to find their way back to your garden.

Aphid on tomato leaf
Aphid on underside of tomato plant.

Again, spray above and below all leaves, being as thorough as possible. I recommend spraying your plants during the early morning to avoid the intense sunlight on the plants. By mid-day, the plants should be fully dried off and (mostly) aphid free.

Spraying aphids off usually doesn’t kill the insects, just kicks them off of their host plant. As a result, aphids will sometimes find their way back to your plants. Keep on top of spraying, once or twice a week, and your aphid problem should be mostly controlled.

For even better results, I always take a few additional measures to help reduce the aphid population and keep them off of my vegetable plants.


Plant Beneficial Plants

Companion planting is a great way to increase the overall health of your garden. There are many naturally symbiotic plant relationships, and some of them can help prevent aphids from choosing your tomatoes as a host.

  • Marigolds are highly attractive to aphids. By planting some nearby your tomatoes, aphids will be more likely to attach to the marigolds, keeping them distracted from your veggies.
  • Yarrow is a great way to attract pollinators and other beneficial insects, including ladybugs. These can help reduce the aphid population by feeding on the insects.
  • Tansy is a natural insecticide and is toxic to arthropods. These include aphids, spider mites, and tomato hornworm. The flowers also attract beneficial insects and pollinators.
Common yarrow with beneficial bugs.

There are many other options, but the goal of companion planting tomatoes is to attract “good bugs” to your garden. They will do a lot better job than you can at finding and removing pesky insects like aphids!


Introduce Predatory Insects

If planting beneficial plants is not an option, there are other ways to get rid of aphids on tomatoes biologically. Ladybugs are the most prevalent and widely used insect for aphid control, and as a result, they are fairly easy to find.

Ladybugs

Live ladybugs can often be bought online, or at some local nurseries or garden centers. Some people question the humaneness of buying live insects, but they are typically kept well fed while in transit.

Tip: When releasing live ladybugs, always do so in late evening when the sun is not out and the weather is cooler. More ladybugs will stay in your garden this way.

As long as there are bugs to eat, some of the ladybugs should stick around and start feasting. Be sure you can also identify ladybug larvae, as they can be even more effective than the full-grown ladybugs at controlling aphids.

Praying Mantis

Another highly effective bug to release in your garden is the praying mantis. You can purchase praying mantis egg cases and attach them to your plants about 2-3 feet above the ground.

Mist the egg cases with water every day or two and the mantises will hatch and begin feeding on any garden pests they can find. Mantises are amazing to watch, as they are very fast and strange looking. They are so ravenous that they are known to eat each other!

The only drawback to praying mantis is that they are expensive to purchase, so if you see them naturally roaming your garden, be sure to protect them!


Spray With Neem Oil (Natural Insecticide)

If you are looking for a natural way to get rid of aphids on contact, neem oil will do the trick. This oil is an all-natural insecticide and fungicide that can be safely sprayed onto the foliage of your tomatoes.

Tip: Always buy organic cold pressed neem oil that contains azadirachtin. This natural compound is contained in neem seeds and is essential for an effective spray.

While neem oil is an effective method for reducing an aphid infestation, it should be a last resort after trying the other methods above. If spraying with water is not enough to stifle the aphid population, neem can add more protection.

Neem Oil Spray Recipe:

Mix these ingredients in a bucket or similar, and use a spray bottle to mist your tomato plant leaves, top and bottom. Do this in the evening after the sun has set to avoid any leaf burns.

Be as thorough as possible to cover all surfaces of the plant. The neem oil works by smothering aphids, so any that are not hit will not be affected. By the morning, the aphids that were hit with the neem solution should be dead.

Note: Some spray bottle may become clogged when spraying oils. If this happens, you can try using a sponge to apply the neem to your plants as an alternate method.


About Aphids

If you deal with aphids regularly, I feel that it is important to understand their life cycle. It helped improve my confidence when treating an infestation.

What Do Aphids Eat?

Aphids are sap-sucking insects that use special, sharp mouth parts to tap directly into your plant. They feed on the phloem tubes that transfer water and nutrients throughout your tomato plants.

Since they are feeding on what is essentially the circulatory system of your plant, they are the perfect vector for introducing viruses.

Aphids commonly carry and transmit plant viruses, including potentially detrimental mosaic and leaf roll viruses.

Note: Aphids excrete ‘honeydew,’ a sugary substance that is attractive to ants. If you see ants on your plants, it may be an indication that aphids are present.

What Eats Aphids?

Everything! Okay, maybe not everything. However, aphids are seen as a tasty snack by many beneficial insects. Some aphid predators include ladybugs, lacewings, praying mantis, and hover flies.

Aphids are an easy snack for predators because most of them cannot fly, jump or otherwise protect themselves in any way. So how do aphids survive if they are so easy to catch and eat? The answer lies in their ability to produce huge numbers.

How Do Aphids Reproduce?

In the early spring, aphid eggs hatch into winged or wingless females. Flying aphids can then find your tomato plants, where they can then begin populating. Aphids can give birth to live young (most of them female), some of which may already be pregnant.

Aphids on tomato leaf
Green aphids on tomato leaf.

Each aphid can then produce several more aphids, making for a very quick population boom. In the fall, aphids lay eggs that survive winter, and the cycle continues on from there.

Without any natural predators to keep populations in check, an aphid infestation can quickly turn into a gardener’s nightmare. Whether you are their primary predator with your squashing thumbs, or you deploy ladybugs, you’ll need something keeping on top of it.


Aphid on tomato plant
Two winged aphids on tomato stem.

I hope this article helps you in dealing with aphids on tomato plants. They can be pesky and annoying, but if you accept that they are natural and deal with the problem accordingly, aphids don’t have to ruin your gardening season. Happy growing!

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