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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Tina.... We NEED your spray recipe, please!!!!
Sincerely,
Brussel Sprouts
What is your spray recipe? We have pollinator gardens and do not use anything to harm pollinators, so I am very interested in what you are using.
Thank you!
yes! Please add your spray ingredients! Thank you.
How do you make your special solution to kill aphids and not kill monarch butterfly eggs or caterpillars?
I have aphids on milkweed which was panted to promote healthy monarch population... I don't want to use anything to harm the butterfly population but need to be rid of the aphids.....
My garden is currently being swarmed by flying whitely. It is so bad that I can no longer sit out to enjoy the sun and garden. A couple of my plants have been attacked but I am treating these and my other healthy plants. It is the number that are flying around that is my problem. Does anyone have any suggestions? I think the May be coming from my neighbors plum tree which is in the opposite side of my fence.
I read that it's the azadirachtin in neem oil (only in cold pressed, not processed) that really works, but you have to treat early with a soil drench so the plant can take it up into the leaves and mess with the aphids' hormone receptors. The pure neem oil that I have solidifies at cold temperatures (basically below like 80, I think), and I'm wondering if it is possible to crumble up the solidified oil into pellets and add that to the soil in the spring before planting?
I would like to know where the scientific studies are that demonstrate catnip, mint, or other Lamiaceae repel aphids. I read this some years ago and I have tested it thoroughly in my own garden and it does not appear to work. Against control plants, I tested a)growing tomatoes in a bed with mint; b)hanging mint from the tomato plants; c) spraying the plants with mint oil. In no case were the number of aphids statistically different from the controls.
Yes, there is scientific evidence that mint repels aphids. Refer to Common Sense Pest Control by William and Helga Olkowski and Shiela Daar, Rodales Encyclopedia of Organic Gardening, Cornell University. It is rather a long read. For catnip, I do know there’s good evidence it does repel potato beetles. Here’s one of many edu articles about catnip deterring aphids: https://aggie-horticulture.tamu.edu/galveston/weekly_Q&A/p&dc_5.htm
Wanted to share my experiences with these awful (kinda cute) insects. My strawberry tree was almost killed by aphids last year as I had noticed too late. When I did notice, the tree’s leaves were black and shiny, many fell off, new leaves were stunted, curled and infested. Then I started to spray with a neem mixture until I saw ladybug larvae all over the tree. They procreated and soon I had about a dozen or more ladybugs working on the tree. So ladybugs do come but in my case, too late. This year, since aphids mostly come in the spring, I was on alert. When the strawberry tree started to grow new leaves, I went to work right away. The key is that you MUST start early. Once they multiply to the point where your plant is shiny with their sticky sweet stuff, and is visibly suffering, it’s too late. You can do what you can but you have to wash your plant (with a bit of dawn in the water to remove sticky aphid stuff), get rid of the ants that will come to farm, and solve your secondary problem of fungus and mold from the sugars. So what I am doing this year is every other day (you must be on it!) I take a gallon sprayer, fill it with water, add a bit of dish soap and a bit of fungicide (to be exact, Zerotol HC) I spray ALL the new leaf areas. Even if I do not see aphids. I check the older leaves as well. So far the plant is growing very good and new leaves are coming in strong. When the leaves are mature, I will slow down the application but for now, I’m out there EVERY OTHER DAY— not more than two days. I’m doing this with all my roses and redbud tree, beans and Swiss chard. Also- Garlic Barrier works ok for aphids but it smells SO strong and the smell will stay in your gallon sprayer. You also must apply frequently. It ruins edible plant taste so don’t spray garlic on Swiss chard for example. Recommending the water, soap, fungicide route.
Hope this helps some. Aphids may be easy to kill, but their strength is in numbers and rate of procreation!!
Good luck in your war!
