Are Aphids Bad for Tomato Plants? Understanding This Common Garden Pest

Aphids are a common pest that can do serious damage to tomato plants. But are they really bad for your tomatoes? Let’s take a closer look at these tiny insects to find out.

What Are Aphids?

Aphids are small, soft-bodied insects that feed by sucking sap from plants. They come in many colors like green, yellow, brown, red or black. Aphids have pear-shaped bodies and long legs. They can be winged or wingless.

There are around 250 different species of aphids. Some species are specialists that only feed on one type of plant. Other generalist aphids feed on multiple plants. The most common aphid species that affects tomatoes is the green peach aphid.

How Do Aphids Damage Tomato Plants?

Aphids cause harm to tomatoes in a few different ways:

• Sucking sap – Aphids have piercing mouthparts that they use to pierce plant tissue and suck out the sap This can weaken and stunt the growth of the plant

• Spreading diseases – Aphids can transmit viral diseases from infected to healthy plants as they feed. These include tomato yellow leaf curl virus and potato virus Y

• Secreting honeydew – Aphids excrete a sticky sugary substance called honeydew. This can coat leaves and fruit encouraging mold growth. Ants love honeydew and will “farm” aphids.

• Deforming plants – Large aphid populations can cause leaves to curl, twist, yellow, wilt or drop. Flowers may not develop properly. Plants become stunted.

So in short – yes, aphids can definitely be bad for tomato plants! An uncontrolled aphid infestation can seriously impact your crop.

Aphid Life Cycle

To control aphids, it helps to understand their life cycle:

• Eggs – Female aphids reproduce without mating, giving birth to live young. But they also lay eggs in the fall that overwinter and hatch in spring.

• Nymphs – The young aphids (called nymphs) look like smaller wingless adults. They immediately start feeding and maturing.

• Adults – Adult aphids have wings that allow them to disperse to new plants. After landing, they shed their wings and begin reproducing rapidly.

• Rapid reproduction – Each female can produce up to 12 offspring per day, allowing populations to explode quickly. The nymphs mature in 7-10 days.

So aphid numbers can go from a few to thousands in just a few weeks. Controlling them early is key.

Signs of Aphids on Tomato Plants

Keep an eye out for these signs of aphid infestation:

• Clusters of small, pear-shaped bugs on the undersides of leaves or on stems. They may be green, yellow, brown, red, black or white.

• Leaves that are curled, wrinkled or deformed. Plants appear stunted.

• White shed aphid skins after molting. These look like flakes on the leaves.

• Honeydew – sticky substance on leaves that attracts ants. Leaves may be shiny or black from sooty mold.

• Yellow spots on leaves or twisted new growth. These can indicate virus transmission.

Inspect the undersides of leaves carefully to spot aphids early before populations explode. Focus on new growth.

How to Control Aphids in Tomato Plants

If you detect aphids on your tomatoes, taking action quickly can prevent major damage. Here are effective ways to control aphids:

Organic Control Methods

• Insecticidal soaps – Soap solutions disrupt the structure and permeability of the aphid’s cell membrane. Spray directly on the insects. May require multiple applications.

• Neem oil – Made from the neem tree, it coats insects in oil and blocks their breathing. Spray young nymphs before populations are high.

• Horticultural oils – These oil sprays smother aphids and larvae. They’re less toxic than chemical pesticides.

• Pyrethrins – Natural chemical compounds that attack the nervous system of insects. Often combined with piperonyl butoxide.

• Attract beneficial insects – Ladybugs, lacewings, hoverflies and other predators feed on aphids. Plant flowers to attract them.

• Strong water spray – Blast plants with water to knock off some aphids. Repeat every few days.

• Row covers – Cover plants with fabric row covers to form a physical barrier. Seal the edges with soil.

Chemical Pesticide Options

• Insecticidal soap – As organic soaps but in stronger concentrations. Requires direct contact.

• Malathion – Broad spectrum organophosphate insecticide. Kills aphids on contact. Toxic to bees.

• Imidacloprid – Systemic neonicotinoid pesticide. Absorbed by plants, kills sucking insects for weeks.

Only use pesticides as a last resort, following all safety directions. Many common products are highly toxic to bees and wildlife. Consider your whole garden ecosystem.

Natural Aphid Control with Companion Planting

Certain plants can help repel or control aphids when planted nearby thanks to the chemicals they emit. Try interplanting these companions:

• Marigolds
• Chives
• Garlic
• Petunias
• Radishes
• Coriander
• Dill
• Nasturtiums

You can also rotate tomato crops each year and remove weeds, which may harbor overwintering eggs. Controlling ants can reduce aphid farming. Use sticky barriers on plant stems.

When to Take Emergency Action on Aphids

Call in the big guns if you notice:

• Heavy infestations of 50+ aphids per leaf
• New colonies rapidly appearing
• Leaves severely curling or yellowing
• Flowers and fruit stunted or dropping
• Signs of virus transmission

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