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How to Identify and Get Rid of Aphids on Plants

green aphids crawling on a plant

Aphids are pesky green bugs that can wreak havoc on your garden.

Image Credit:
Pixabay
Written By: Catherine Boeckmann Executive Digital Editor and Master Gardener

What are those little green bugs on your plants? They’re probably aphids! Here are our best tips for identifying and getting rid of aphids in your garden.

What Are Aphids?

Aphids seem to find their way into every garden. They are small, soft-bodied insects that feed by sucking the nutrient-rich liquids out of plants. In large numbers, they can weaken plants significantly, harming flowers and fruit. Aphids multiply quickly, so getting them under control before reproduction starts is important. Many generations can multiply in one season.

Lee Townsend, an Extension Entomologist at the University of Kentucky College of Agriculture, explains, “Infestations generally result from small numbers of winged aphids that fly to the plant and find it to be a suitable host. They deposit several wingless young on the most tender tissue before moving on to find a new plant. The immature aphids or nymphs that are left behind feed on plant sap and increase gradually in size. They mature in 7 to 10 days and then are ready to produce live young. Usually, all of them are females, and each is capable of producing 40 to 60 offspring. The process is repeated several times, resulting in a tremendous population explosions. Less than a dozen aphid “colonizers” can produce hundreds to thousands of aphids on a plant in a few weeks. Aphid numbers can build until conditions are so crowded, or the plant is so stressed, that winged forms are produced. These winged forms fly off in search of new hosts, and the process is repeated.”

The good news is that aphids tend to move rather slowly and, with diligent care, can be controlled.

Identification

Identifying Aphids

Aphids are tiny (adults are under 1/4 inch), and often nearly invisible to the naked eye. Various species can appear white, black, brown, gray, yellow, light green, or even pink. Some may have a waxy or woolly coating. They have pear-shaped bodies with long antennae; the nymphs (young aphids) look similar to the adults. Most species have two short tubes (called cornicles) projecting from their hind end.

Rose Aphid on a plant
A close-up view of a rose aphid.

Adults are usually wingless, but most species can develop a winged form when populations become crowded, so that when food quality suffers, the insects can travel to other plants, reproduce, and start a new colony. Aphids usually feed in large groups, although you might occasionally see them singly or in small numbers.

While aphids in general feed on a wide variety of plants, some species of aphids can be specific to certain plants—for example: bean aphids, cabbage aphids, potato aphids, green peach aphids, melon aphids, and woolly apple aphids.

dark brown aphids on a leaf with a hand holding it
Some aphids are darker colors, like brown. The potato aphid is a common brown aphid. 
Photo credit: GrowVeg.com.

What Does Aphid Damage Look Like?

Nymphs and adults feed on plant juices, attacking leaves, stems, buds, flowers, fruit, and/or roots, depending on the species. Most aphids especially like succulent new growth. Some, such as the green peach aphid, feed on a variety of plants, while others, such as the rosy apple aphid, focus on one or just a few plant hosts.

  • Look for misshapen, curling, stunted, or yellowing leaves. Be sure to check the undersides of leaves; aphids love to hide there.
  • If the leaves or stems are covered with a sticky substance, that is a sign that aphids may have been sipping sap. This “honeydew,” a sugary liquid produced by the insects as waste, can attract other insects, such as ants, which gather the substance for food. When feeding on trees, aphids’ honeydew can drop onto cars, outdoor furniture, driveways, and so on.
  • The honeydew can sometimes encourage a fungal growth called sooty mold, causing branches and leaves to appear black.
  • Flowers or fruit can become distorted or deformed due to feeding aphids.
  • Some aphid species cause galls to form on roots or leaves.
  • Aphids may transmit viruses between plants.
  • Aphids also attract other insects that prey on them, such as ladybugs.
yellow aphids on a plant leaf
Aphids can be various colors, including yellow, and produce a sticky honeydew substance. 
Photo Credit: John Obermeyer/Purdue University.

Still not sure? Use our Plant Problem ID tool to easily diagnose pests and diseases.

Control and Prevention

How to Get Rid of Aphids: Killing Aphids

  • Try spraying infested plants with a strong stream of water; sometimes, all aphids need is a blast to dislodge them. Typically, they are unable to find their way back to the same plant.
  • Neem oil, insecticidal soaps, and horticultural oils are effective against aphids, but these substances need to come into contact with the aphids in order to work. Be sure to follow the application instructions provided on the packaging.
  • You can often control aphids by wiping or spraying the leaves of the plant with a mild solution of water and a few drops of dish soap. Soapy water should be reapplied every 2-3 days for 2 weeks.
    • One variation of this soap-water mix includes cayenne pepper: Stir together 1 quart water, 1 tsp liquid dish soap, and a pinch of cayenne pepper. Do not dilute before spraying on plants.
  • Diatomaceous earth (DE) is a nontoxic, organic material that will dehydrate aphids.
    Warning: Do not apply DE when plants are in bloom, as it will kill pollinators such as bees and butterflies if they come into contact with it.
thumb over the end of a garden hose spraying water
Hosing down your plants is one way to control the aphid population in your garden.

How to Prevent Aphids

  • For fruit or shade trees, spray dormant horticultural oil to kill overwintering aphid eggs.
  • Beneficial insects, such as ladybugs, lacewings, and parasitic wasps, will feed on aphids. Attract these insects to your garden by providing an environment that features a range of flowers and foliage plants, as well as access to water. Supplemental populations of these insects can be ordered online and should help control the aphid populations from the start.
  • Companion planting can help keep aphids away from your plants in the first place, or can draw aphids away from the plants you want to grow. For example:
    • Aphids are repelled by catnip.
    • Aphids are especially attracted to mustard and nasturtium. Plant these near more valuable plants as traps for the aphids. The aphids will likely go for these plants before your prized tomatoes. (Check your trap plants regularly to keep aphid populations from jumping to your valued plants.)
    • Nasturtiums spoil the taste of fruit tree sap for aphids and will help keep aphids off of broccoli.
    • Garlic and chives repel aphids when planted near lettuce, peas, and rose bushes.
Ladybug larva
Ladybug larvae look scary, but they are one of the top aphid predators. If you see them on your plants, leave them be! 

Using Alcohol to Control Aphids

Isopropyl alcohol (also called isopropanol or rubbing alcohol) works fine and is easy to find, but be sure it doesn’t have additives. Ethanol (grain alcohol) seems to work best. Alcohol usually comes in 70 percent strength in stores (or 95 percent strength purchased commercially). To make an insecticidal alcohol solution, mix equal parts 70 percent alcohol and water (or, if using 95 percent alcohol, mix 1 part alcohol to 1 ½ parts water). 

You can also add alcohol to a soapy emulsion to make it more effective. For example, in a spray bottle, combine 5 cups water, 2 cups isopropyl alcohol, and 1 tablespoon liquid dish soap. 

These types of solutions should NOT be sprayed over the entire plant at once. Spray or wipe down only the infested areas. It will only kill the aphids it comes into contact with, so repeated applications may be necessary.

CAUTION: When applying an alcohol or soap spray, or a combination, always test on a small area of the plant first, and apply in the morning or evening, when the Sun is not as intense. Watch the plant for a few days for any adverse reactions before applying more. Plants can be sensitive to alcohol and dish soap. Also, some soaps have additives that can damage plants—select the purest form.

Check out this video to learn more about how to get rid of aphids:

Do you have more tips for controlling aphids? Let us know in the comments below!

Garden Pests

About The Author

Catherine Boeckmann

Catherine Boeckmann

Executive Digital Editor and Master Gardener

Catherine Boeckmann is the Executive Digital Editor of Almanac.com, the digital home of The Old Farmer’s Almanac. She leads digital editorial strategy and publishing across a wide range of Almanac sub...

Read more from Catherine Boeckmann

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Comments

<a title="View user profile." href="/author/editors">The Editors</a> Tue, 04/29/2014 - 07:15

Aphids do tend to be troublesome in cool, dry weather. You need to catch them early and spray foliage with soapy water, then rinse with clear water or use insecticidal soaps. You could also fill yellow pans with water to trap the aphids.
On a bigger scale, you'd need to investigate two or three insecticide treatments at five-day intervals may be needed to clean up plants.
Be sure to clean up plants immediately after any harvesting. We hope this works out!

 <span>Catherine Lloyd</span> Sat, 04/19/2014 - 04:33
For the first time last summer our laburnum tree was infested with aphids. Is this likely to happen again this summer?
<a title="View user profile." href="/author/editors">The Editors</a> Tue, 04/22/2014 - 06:17

This tree is relatively pest-free but it is indeed susceptible to aphids. We would visit your local nursury for an organic spray.

 <span>Skylar</span> Sat, 03/22/2014 - 13:40
Hi, iv just started a garden and im growing sunflowers. Iv noticed the plants leaves were getting eaten and my plants are starting to die.iv tried spraying water on it with the hose and it helped some but only a little. I want to start growing herbs but I dont want the same thing to happen. Iv found two small caterpillars. Is there a spray I can get that kills bugs but is plant-safe? Preferably at home depot.
<a title="View user profile." href="/author/editors">The Editors</a> Mon, 03/24/2014 - 17:38

If you see aphids, try a soap spray every 4 to 5 days. You can even make your own: water and 2-3% washing up detergent.

However, it sounds as if you have caterpillar damage. Pick them off twice a day with gloves and drop them in a bucket of soapy water. If this doesn't work, ask Home Depot for a BT spray (Bacillus thuringiensis) which is considered a low danger to honeybees and beneficial insects.

 <span>Mark Fulop</span> Sun, 02/02/2014 - 16:28
Aphid and Mite problem! I just purchased about 1500 lady bugs. Maybe they helped a little but there are only a few left after a week or two. They were in a green house where did they go? There is also a mite problem on my strawberries. My set up is a hydro ponic ebb and flow system in my green house in NJ. We are growing about 50 strawberries, dozen tomatoes, A few Brussels sprouts, cantaloupe, watermelon, cucumber, and basil. What works is looking through each plant and cleaning each leaf with my hands and squeezing the aphids or breaking off the leaves that infest. I am constantly killing them but they are still there. The mites make a web across the leaves of the strawberries. I clean the web off with a spray bottle and my hands. There still are leaves that have turned brown but they have not killed my plants. I was thinking about calling the lady bug people back and telling them the bugs died too quickly and to send more. My fear is that they eat the new flowers for strawberries and tomatoes. Therefore, the plants will never bear fruit because they are working against me. Its a hobby but I also wanted to see something out of my efforts. The entire system that I build cost about 3500 dollars. Overall my light bill for two 600 watt grow lights costs about 170 per month. My next step is to look into insecticidal soap. What is your opinion?
<span>Heathers</span> Wed, 08/13/2014 - 15:49
Sounds like the mites you have are spider mites. The only organic method I've found that works to kill them is Neem oil. Or squishing them & the web, but that can get tedious & doesn't really help with a bad infestation. For aphids, I either squish them and/or use a home made insecticidal soap made from castile soap diluted with water. Castile soap (or any type of soap) basically causes the insect's cell membranes to 'break' so the insects die of dehydration. I usually use peppermint castile soap, as the peppermint oil in the soap seems to intensify the effect of the soap. I usually use 1-2 Tbsp per quart of water. Also, I've read in a number of places that insects are territorial & generally define their territory by where they 'hatched'. Did the ladybugs come fully grown or were they nymphs or eggs? If they were fully grown, that might be why they didn't stick around for long. :(
<a title="View user profile." href="/author/editors">The Editors</a> Thu, 02/06/2014 - 16:54

Hi Mark,

We suggest that you call the lady bug people back and tell them what happend to see if they have any suggestions.

Insecticidal soap, if used according to directions, will cut back on your pest problems. Also read some of the comments on this page to find out what other readers have tried.

Good luck!

 

 <span>Samantha Pedroza</span> Wed, 11/20/2013 - 18:13
Hi yes I'm curious, I have an above ground garden in my apartments the floor is cement then I used bricks and wood pallets to make it. I've finally started to yield my chiles and after my first harvest another round of buds came out...and that's when the infestation started. First ants then black tiny little bugs I'm assuming are the aphids. I've done everything but nothing seems to be working I tried an insecticide I tried cold water showers I tried the alcohol water soap solution and nada and it's making my plants growth stunt. Helllppppp
<a title="View user profile." href="/author/editors">The Editors</a> Fri, 11/22/2013 - 15:51

Aphids are common pepper pests though they usually look like tiny whitish specks, not black. See the picture on this page. Spray a mild solution of soapy water on all sides of the leaves, especially the undersides.  If the infestation is severe, spray with pyrethrum.
Tiny black specks are probably flea beetles. You can dust with wood ashes or spray with a garlic or hot pepper solution. Spraying with pyrethrum will also control flea beetles.