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Aphids on Tomato Plants: How to Identify and Control Them

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Tiny pest. Big damage. Aphids on tomato plants can stunt your crop and cause leaves to curl. That’s one good reason they’re also called “plant lice.”

Of 4400 aphid species, 250 are harmful to plants, which is why you may see white aphids on tomato plants … black aphids on tomato plants … red aphids on tomato plants … non-flying aphids along with winged aphids on tomato plants.

And, these buggers just won’t quit. Aphids are very prolific. Females can give birth to up to 80 offspring a week. That’s a whole lot of aphid nymph mouths to feed, especially when you don’t want your tomato plant to be part of the aphid nursery. And all those nymph babies can turn into adults in just 7 or 8 days. 

The good news is that your tomato plants can recover from an aphid attack. If you discover aphids on tomato plants, you can take steps to escort them away. Plus, you can take measures to minimize aphids in your garden. But first …

What do aphids look like?

Aphids are small (2-4 mm), pear-shaped, soft-bodied insects. They can be green, gray, black, brown, yellow, or white – often mimicking the color of the plant they feast on.  They don’t limit themselves to tomatoes. You can find aphids on cucumbers, squash, melon, peppers, potato, and a host of other crops. 

They flourish in colonies. You won’t see one or two aphids. You’ll see a mass.

Where do you find aphids on tomato plants?

Check the undersides of tomato leaves, the crevices and sides of stems, and inside your tomato plant’s blossom. Aphids favor the newer parts of the tomato plant over older, established growth. Newer leaves and stems are more tender and easier for aphids to attack.

What do aphids do to tomato plants?

• Aphids use their mouthparts to eat sap. They suck out juices and nutrients from tomato leaves, stems, and fruits.  Their sap-sucking stunts plant growth, causes leaves to curl, and makes leaves turn to yellow. 
• Plus, as aphids use their snouts to penetrate your tomato plants, they often transmit viruses like the tomato yellow leaf curl virus, the cucumber mosaic virus, the potato virus, and the tomato etch virus.
• And aphids keep on giving.  They secrete a white stick substance called honeydew. Left unchecked, honeydew attracts other pests like ants and leads to sotty mold and powdery mildew on your tomato plants.

Clearly you want to avoid hosting these critters in your garden.

When do aphids do their work?

Aphids are most productive in the spring and fall. They back off during hot weather.

How to get rid of aphids on tomato plants

You’ve got several treatment options you can use to get rid of aphids on tomato plants naturally.

• Handpick aphids on tomato plants using tweezers. It’s tedious. But if you have a large colony, you can nab multiple aphids with each pluck and crush them.
• Spray affected areas with a strong stream of water from your garden hose to knock aphids off plants. Be sure to direct the spray to all parts of the plant, including leaves’ undersides. You may need to repeat this process daily for a week or two, but aphids will depart. Water also dissolves aphid honeydew. Why won’t they just crawl back? It’s just too hard for them. Most aphids take up residence in your garden by being transported by a breeze or because they are born there. 
• Spray plants with insecticidal soap, Neem oil, Castille soap, or other horticultural oils. These products contain fatty acids. Oils and soaps dissolve an aphid’s outer surface, which suffocates them. A solution of 1-2% of the product to 98-99% water will impact aphids.
• Prune tomato branches that are infected with aphids and destroy them.
• Drape tomato plants with row covers which allow plants access to sun, air movement, and water – but provide a barrier to pests.
• Spray tomato plants with organic insecticides like Bonide pyrethrin. Follow manufacturer’s directions.

A home remedy for aphids on tomato plants

Home improvement expert Bob Vila recommends making your own insecticidal spray by mixing 1 tablespoon regular dish soap with 1 quart of water. Apply the mixture with a garden sprayer to your plants every day or two until your aphid infestation disappears.

While this home remedy for aphids on tomato plants is certainly cost-effective, be aware of a couple of things.

First, most dish soaps do not contain fatty acids. Soap particles attach less effectively to aphids, meaning your attempt at suffocation by dish soap may take a couple of tries. And many dish soaps contain fragrance, hand softeners, degreasers, or antibacterial agents, which can slow effectiveness and in some instances even harm plants. Best soap to use: Castille soap, which is made from vegetable oils and will adhere to aphids.

Another option: create a solution of one part rubbing alcohol and nine parts water. Any stronger may injure plants. Apply your rubbing alcohol spray to a test leaf. Leave it for two days to make sure leaves don’t get damaged. When all looks good, then apply to the entire plant. You can repeat the application about once a week. Rubbing alcohol, like fatty acids, works to melt insects’ exoskeletons, which dehydrates them.

How can you prevent aphids on tomato plants?

• Check your plants every time you water them or pick fruit. In particular, look at the undersides of leaves – especially the new ones. That’s where aphids start their destruction. These tiny pests work quickly. That’s why you need to be vigilant.
• Grow good neighbor companion plants near tomatoes.  Nasturtiums, marigolds, basil, garlic, mint, onion, rosemary, chives, catnip, and sunflowers repel aphids.
• Introduce or encourage beneficial insects to your garden – those who like to munch on aphids, including ladybugs, hover flies, and lacewings.
• Set out yellow sticky boards or yellow sticky tape around your tomato plants to attract aphids. They will attach to the tape and die.
• Use reflective silver-colored mulch around the base of tomato plants. Reflective colored mulch is sold in rolls. You can also spray paint plastic a silver color. The shiny surface repels aphids.
  
  

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