Aphids are pesky green bugs that can wreak havoc on your garden.
Preventing Aphid Infestations in Your Garden
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.
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.
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.
Photo Credit: John Obermeyer/Purdue University.
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.
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.
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!
Catherine Boeckmann
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That’s the crazy coolest thing I’ve heard all season! Take a movie next time you catch them in the act?
If the buys have tiny light green bodies and little black eyes, those are indeed aphids. Follow the advice on this page.
We have a ton of aphids nesting in the buds of our Shasta daisies. A bunch of ladybugs have taken up residency as well to eat the aphids, but there are so many that I fear our ladybugs aren’t going to be the full solution. Are any of these mixes (dish soap/water/cayenne) going to harm the ladybugs as well? I don’t want to hurt them if I can help it.
Are green white striped catapillers harmful to Basil plants
The agents you name could harm the ladybugs. Alternatively, you could put out some borax ant bait traps. Read other comments below to acquire more knowledge about what works.
Acticle states use catnip to repel aphids, but my problem my catnip patch is what has been invaded badly.....
It has been suggested that pyrethrum (made from chyrsanthemums) could be effective on catnip.
I have been struggling with aphids in my kitchen primarily for a long time. Brought in on some flowers they seem to be around my windows. I have no house plants so they seem to be living independent from that. I've tried the soap and water thing but to no avail. They are many in number and are now moving to other windows in my home. Help!
If you think you have aphids hiding out in your house somewhere, try dusting what you think to be the affected areas with diatomaceous earth (which is totally pet-safe and should make a border the aphids can't cross without dying) or spraying the affected areas every few days with a neem oil solution if you can get it and don't mind the smell.
Hi I have a very large tree in my back garden and it is full of aphids , never hard this before you can't sit outside without them crawling all over you how can I get rid of them please help me they are driving me mad , they are all over the paving and my outdoor setting they are everywhere help
