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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For the past 4 years I have been battling aphids on my apple tree. There are black aphids and wooly apple aphids I have been using neem oil and spot treating with rubbing alcohol. I have not been successful controlling them. The tree is covered with moss and ferns (the look is beautiful) while talking to my gardener about this he told me that I need to remove the moss, as the bugs are probably hiding in it. So my question is — should I remove the moss? What is the best method? These bugs are effecting my fruit crop and I would like to get more apples Any suggestions are welcome
yes, of course remove the moss. It's hurting the tree.
I first noticed these little black pests that are about two millimeters long when my rose leaves began turning yellow and falling of. I treated my rose for fungus at first but that only got rid of the yellow leaves for a week or two. Now, my plant is experiencing stunted growth and some leaves are turning brown at the tips despite a regular watering regimen. I also noticed that these little black aphids are more prevalent. Should I try diatomaceous earth since there are no new blooms?? Are should I stick to the soapy water method??
Aphids are polyphagus, majorly destructive to most of the kingdom Plantae in the tropical and mid equatoral zone in East Africa.
I was unexpectedly away several weeks this summer, and upon return my kale and broccoli and even rutabaga (planted near the kale) have massive globs of gray aphids at base of leaf stems and lots of gray things on the leaves. I thought it was eggs of the cabbage worm, but have seen only a few worms and worm droppings. Now I believe it is aphids. I have pulled out all plants - should I burn them? Or just put out in woods far from my garden? Also I see tons of them in the soil around where the plants were. Will they overwinter? If so, what can I do now? Dust with diatomaceous earth?
For small plantings, you can try hosing the aphids off plants ever so often. Insecticidal soap can also help. Diatomaceous earth (food-grade, not pool grade) also is an option: for more information about this method, check this page: /blog/gardening/garden-journal/what-diatomaceous-earth You can also encourage beneficial insects by planting nectar-rich plants nearby, such as alyssum. As to how to dispose of aphid-infested plant debris, you can toss it in the trash, or bury it deep in a compost pile. Aphids overwinter as eggs, often laid on trees or shrubs.
They are everywhere these trees are huge, how do we get rid of them.
It's going to be challenging to get rid of them in your case. Make sure you have aphids first. Once you verify they're aphids, try getting a hose attachment that you can add a treatment to, such as 2 tsp dawn soap + 1 cup isopropyl alcohol + 3 cups water (increase amounts in those proportions.) If you're in drought or water shortage, you can also try running misting tubes (usually meant for watering at ground level) up the trees and, again, use that mixture -- you might be better able to cover a larger area that will stick to the trees by misting them. Anything you can do to coat the trees and make them uninhabitable to aphids will help. Fortunately, we live in a creative time of ingenuity. You might even be able to find some sort of misting contraption (like they have for mosquitoes) that emits something that aphids don't like, and hang that in your trees. You'd be surprised what you can find if only you look around. After that, see if you can get some ladybugs - release them at sundown in your trees, right on top of the aphids if you can. Ladybugs are safe and good bugs, but don't put them on your trees before spraying or dusting them.
I need help getting rid of a pest on my miniature rose house plant. I'm not sure if they are aphids. They look like miniature flies. They are more brown/black and fly around like crazy. I don't really see any bugs on the leaves. Are these still aphids and how should I get rid of them?
It sounds like you could be dealing with fungus gnats! Check out our pest page for tips on getting rid of them: www.almanac.com/pest/fungus-gnats
