How Do I Get Rid Of Aphids On My Tomato Plants?

Lots of people grow tomatoes because homegrown tomatoes taste better than store-bought ones. Tomatoes are easy to grow in pots or in the ground but do have some pest problems. This guide will tell you all about aphids and how to get rid of them. 

How Do I Get Rid Of Aphids On My Tomato Plants?

Most of the time, aphids are not enough of a problem to justify treatment. You can use cultural and biological controls to keep the aphids in check. Many times, you can use water to wash them off of your tomato plants. When they do need to be killed, neem oil, horticultural oil, insecticidal soap, and pyrethrins will kill them with the least environmental impact. 

What Is An Aphid?

Aphids are small insects that measure between 1/16-1/8 inches long. They are pear-shaped and have soft bodies. Some aphids are winged, and some do not have wings. Aphids come in different colors, including green, black, red, yellow, brown, or gray.  

Aphid Lifecycle

Aphids reproduce rapidly. The females give birth to live young all summer without mating. In the fall, they mate and lay eggs that will live through the winter. In warmer climates, aphids may produce live young all year. When the plant aphids are on gets crowded, winged aphids are produced. They are poor flyers but can float on the wind for miles before colonizing another plant. 

Aphids on Tomato Plants

Potato aphids

Potato aphids are common on tomato plants. They are 1/8 inch long and may be solid pink, green and pink mottled, or light green with a dark stripe. 

Green peach aphids

Green peach aphids are also common. They are about the same size as potato aphids but are pale yellow to dark green. 

Signs of Aphids on Tomatoes

Aphids use piercing mouthparts to pierce the plant surface and suck the sap out of the leaves and stems. They are typically more of a nuisance than anything, but they can cause a problem if the infestation is severe.

  • Severe infestations cause
  • Sticky leaves
  • Stunted or curled leaves
  • Yellowed leaves
  • Leaves with dead spots in them
  • Stunted or dead shoots
  • poor growth
  • Sooty mold may grow on the honeydew aphids excreted, covering the plant leaf and blocking photosynthesis.
  • Ants are attracted to the honeydew and may protect the aphids against predators.
  • Aphids can transmit viruses to tomato plants.
  • Aphids cause more problems in seedlings than mature plants because seedlings do not have much foliage to spare. 
ants tending aphids
Ants tending aphids

How Do I Get Rid Of Aphids?

The methods to get rid of aphids can be grouped into cultural controls, biological controls, and chemical controls. 

Cultural Controls

Cultural controls are things you do to change the environment to keep aphids down.  

  • Silver or aluminum-colored mulch repels aphids. You lay it down as a sheet, then make two-to-three-inch holes in the mulch and plant a tomato plant in each hole. The mulch isn’t effective when more than 60 percent of it is covered with foliage, but it can give tomato seedlings a crucial start that is relatively aphid free. 
  • You should monitor your tomato plants at least twice a week for aphids. When you start to see them, a blast of water will wash most of them off your tomato plants. Be careful not to damage the tomato plant with the water. 
  • Keep weeds removed from your garden area. Mustard and related plants are especially bad about serving as places for aphids to grow before they attack your tomatoes. 
  • Plant a selection of flowering plants that bloom all through the season to serve as a place for predators that will eat your aphids to feed and reproduce. 
  • Be careful with your fertilizers. Aphids tend to be more common on plants fed lots of nitrogen fertilizer because the succulent new growth is tasty 
  • Yellow sticky aphid traps can be put out when the seedlings are planted to catch windborne winged aphids before they reach your plants. 
Lady beetle eating aphids

Biological Controls

Lady beetles, lacewings, praying mantises, syrphid fly larvae, and parasitic wasps all eat aphids. As mentioned above, planting flowering plants near your tomato plants will attract these natural enemies. 

You can purchase natural aphid predators, such as lacewings, praying mantises, and lady beetles, at online garden supply firms, but unless they have aphids to eat along with flowers to rest and reproduce in, they will soon fly away.   

Chemical Controls

Chemical controls include both organic and synthetic controls.

Naturally occurring pesticides such as neem oil and pyrethrins are permitted in organic gardens. Be careful using neem oil in hot temperatures as it can cause burns on the leaves. Some insecticidal soaps and horticultural oils are also allowed in organic gardens. They can also burn your plant when it is hot. 

Synthetic pesticides for aphids include bifenthrin, cypermethrin, cyhalothrin, permethrin, and esfenvalerate. Do not use permethrin on tomatoes with fruit that is less than one inch in diameter. Sevin dust used to kill aphids, but many of them have developed resistance to it, so Sevin dust is no longer recommended. 

Keep in mind that pesticides, whether they are organic or not, can kill bees and aphid predators. If you must use pesticides, spray them in the evening after bees have stopped foraging. Make sure you get the spray on both the top and underside of each leaf and stem. 

Homemade Aphid Spray

While commercial sprays are easier to use, you can make an effective aphid spray. Here is a recipe given by the University of Hawaii Extension. 

Mix one tablespoon of mild dishwashing liquid (Ivory, for example) with one cup of food oil (peanut, corn oil, sunflower oil, or canola oil). Do not use Dawn ultra or any ultra dishwashing liquid. Shake the solution well to mix the detergent with the oil. 

Take one to two teaspoons of the oil and mix it with one cup of water. Shake well and spray on the tomato plant. Repeat once a week for three to four weeks.  

Will vinegar kill aphids on tomatoes?

Yes, but it will also kill your tomato plants. Do not apply vinegar to any part of your tomato plants. 

How To Prevent Aphids on Tomatoes?

Preventing aphids is difficult because they are so widespread and travel on the wind. Prevention consists of implementing the cultural controls recommended above: weed control, silver or aluminum colored mulch, planting flowering plants in with the tomatoes, using yellow sticky traps, and being careful with your fertilizer. 

In conclusion, aphids rarely reach levels that damage tomato plants, unless they attack seedlings. Using cultural and biological controls is the easiest way to deal with them. Chemical controls should only be used when the tomato plant shows signs of severe infestation. Using neem oil, insecticidal soap, or horticultural oils will kill the aphids with the least environmental damage.  

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Stephanie Suesan Smith

Stephanie Suesan Smith has a Ph.D. in psychology that she mainly uses to train her dog. She has been a freelance writer since 1991. She has been writing for the web since 2010. Dr. Smith has been a master gardener since 2001 and writes extensively on gardening. She has advanced training in vegetables and entomology but learned to garden from her father. You can see her writing samples at https://gardencopywriter.com/garden-writing, and her vegetable blog at https://stephaniesuesansmith.com/.

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