How to control Aphids? Flawlessly, every year, from April to June this question dominates my work, encompassing the concerns of professional growers, landscapers and home gardeners. Aphids are so common, and there are so many species affecting so many plants. Home gardeners often make the mistake of not associating their winged stage with the typical non-winged stage, and not recognizing that aphids can be different sizes, colours and shapes and some are specific to only one or two kinds of plants. Aphids are complicated; they are sticky and damaging, unsightly and overwhelming; and here is how to control them:
Seriously. Take a stream of water from a hose and with a little pressure, wash them from the leaves. This sounds too simple, and you’ll be asking “won’t they survive and climb right back up?” Trust me: If you are looking up how to control aphids because you have an aphid problem at the moment, stop reading and go spray them off with water. I list this first because it’s something you can do now that will help and not prevent other control methods from working. Do it now. Then read further.
Watch: Scouting for Aphids
Spraying them off with water does several things: First, aphids continually feed by sucking plant phloem (sap) through straw-like mouth pieces. They seldom mate or lay eggs, but just produce live birth clones. When the feeding is good, they reproduce rapidly. Spraying them off with water interrupts their feeding and slows their reproduction. Second, many of their mouth-pieces will break off in the leaf tissue, so while they may climb back up, they will still starve. Third, as this water may also injure or disrupt aphid predators, you are not applying a soap or any chemical and home remedy that will kill off predators or stress your plants. Furthermore, when you find aphids, I can guarantee you aren’t the first to notice them. Many will already be parasitized, predators will be present or their eggs and larva will be, so knocking the aphids off the plant does not prevent the parasitoids from emerging, or prevent the predators from feeding on them and establishing in your yard. Essentially, spraying with water is buying you and your plant time. Your plant will not suffer damage as quickly and the natural predators (who will eat all the aphids eventually….even if you do nothing) will still come and do their job.
Release Predatory Midges
Aphidoletes aphidimyza is the top biological control for aphids. Not ladybugs! (Never buy ladybugs) In almost all commercial greenhouses, nurseries, public and private gardens Aphidoletes has been the primary aphid control for several decades. They are inexpensive, easy to use, and they do all the work for you.
Aphidoletes arrive as pupae. Within a day the adults (which look like mosquitos) emerge and mate within the container. You simply open up the container in your yard or greenhouse (best to do so at dusk). You don’t even need to release them close to the aphids. The adults find aphids by the smell of the honeydew. So, as long has you haven’t sprayed the plant with a soap or smelly compound which masks their smell, the Aphidoletes will find the honeydew, feed on it and lay hundreds of eggs in the aphid colony. Each egg hatches into an aphid-destroying larva capable of killing hundreds of aphids in their short 7 day larval stage. At that point they drop to the ground to pupate in the soil and they start the process over again.
If you like the idea of releasing beneficial insects to control aphids, then Aphidoletes is best.
There are other beneficial insect options too:
Release Brown Lacewing Adults.
The Brown Lacewing adult is an aphid predator. It finds and eats aphids. It also lays eggs and its larva are incredible aphid predators. Similar to Aphidoletes, you just open a container and they fly-out, find aphids and go to work. This is a little less satisfying than Aphidoletes since they are hard to find after release and control takes longer. They are also the only cold-weather bio-control for aphids. They are excellent for cold-weather fox-glove aphid.
Release the American Hoverfly
Eupeodes americanus is an unmatched aphid predator. Each worm-like larva can eat as many as 2200 aphids in their 7 day larval stage. However, like Aphidoletes, these are packaged as pupa. The adults you get are not aphid predators, but fantastic pollinators. They need pollen and nectar for 3-5 days before they lay the eggs that will result in aphid control. Best applications are still being researched, but these are great if you have lots of flowers or kids that like bugs! Otherwise, shop for Hoverfly Eggs to apply directly to aphid colonies.
Release Aphidius (or wait for them)
Some Aphidius species are available commercially. They are tiny parasitoid wasp that parasitize aphids. You have likely seen them, since they often show up naturally. They are the little bronze/brown, rounded aphid bodies that you see in aphid colonies or where they were. In the right conditions they can spread easily as each adult can parasitize many aphids. The only draw back is they are specific to specific types of aphids, and their mummies remain on the plants after the aphids are gone. This is not ideal for ornamentals or edibles, but might work for you. However, a gut bacteria found in aphids, known commonly as Hamiltonella, prevents aphids from being parasitized. And while this was found in only a few specific areas, it has since been discovered in aphid colonies all over the world.
Use a bio-pesticide
These are becoming highly popular. Essentially you spray the leaves with a parasitic fungi. When aphids (and other soft bodied invertebrates) come in contact with it…and conditions are right…the fungi infects and kills the aphids. The draw backs to this is they don’t specifically target aphids, and you’ll be killing many other insects you might want around. It can also be expensive, and the more these are used the more resistance is created. Some common names are Beauvaria or Metarhizium.
I know, right!? Aphids serve one purpose: to feed other animals. Birds love them, bugs love them, you’ll even find other small animals feeding on them or their honeydew. Although unsightly, aphids almost never kill a plant (except young seedlings). A bit of tolerance for aphids usually results in you finding aphids, seeing their population grow and then seeing them disappear slowly or overnight as predators eliminated them naturally. Aphids also come earlier in the year than predators so that their populations can increase in order to feed everything – this is the natural cycle of aphids. Whenever you can leave them, do. For example, the native ladybugs (not the ones you buy) have several life cycles during the growing season. They eventually have large enough numbers to cause massive reductions in aphid populations. But early in the season, there are few ladybugs, and lots of aphids. This is normal.
Aphids also are sometimes specific to plants. For example, the hop aphid can only infect hops. The lupin aphid only affects lupins. The oat aphid affects only grains. So, my master-growing-tip: Plant these. Put them places where you won’t care how damaged they get and watch them attract predators. My hop gets the hop aphid, and then ladybug eggs show up, then their larva, then the adults, then more eggs and suddenly my yard is inundated with thousands of free aphid predators that will move to aphids that ARE a concern on other plants, like the green peach aphid, pea aphid, or that black aphid that seems to affect all plants in your garden. And don’t necessarily pull that one Brussel Sprout covered in cabbage aphid. If the other plants are clean be confident that the aphids are attracting predators. That Brussel becomes your one sacrificial one. (If you don’t have a sacrificial one, just plant a couple extra next year.)
Aphids feed on the phloem in plant tissue (the sap). The more nutrients that plant is taking up, the more it is feeding aphids. In a garden growing in natural, lean soil, aphid (and other sucking insects, like spider mites and whitefly) do poorly. But in rich soil amendments, like manure, or liquid, quick fertilizers, you are feeding insects as well as your plants. One of the first steps in aphid management in a greenhouse is to reduce the nitrogen component of the fertilizer: the speed that aphids reproduce is reduced immediately. In a yard, consider this next year: grow plants lean. They might be smaller, but they won’t be less attractive. When you use a quick fertilizer then stop providing it is when leaves turn yellow. That is not the case when they grow lean from the beginning. See more on this and all the goods on fertilizer here.
Talking about Aphids is part of my job. I do it endlessly, and while everyone’s concerns about aphids are high and their individual situations complicated, aphid control is always so simple. I assess a situation and suggest either spraying dense populations off the plant with water and doing nothing else, or releasing Aphidoletes, the predatory midge. In a protected structure like a greenhouse you must use Aphidoletes because other predators will have a hard time finding their way inside. Outside I usually suggest doing nothing, but when people have a high value plant (commercially or aesthetically) or a specific need, like hosting a patio dinner under a tree dripping honeydew from aphids, or a yard with a history of high aphid pressure, then I use Aphidoletes outdoors. Fortunately in most of Europe and North America, one, single release of Aphidoletes (maybe costing you $30) can be all you need until that population disperses 5 years later.
But this only sounds simple, because true problems with aphids are from situations made complicated by our own interventions. A few seconds of internet searching and you’ll find a “home remedy” for aphids. It’ll be a combination of household ingredients turned into a spray. Yes, this will kill aphids (usually) but it is no different than using a harsh chemical: the aphid fix will be temporary, but the affect to your plant and natural predators will be long-lived. The “active ingredient” in a chemical aphid spray is usually effective for the first few years after it is created and then there is aphid resistance. However, the chemicals work longer because of the other ingredients – primarily water and a spreader (used to produce fine droplets) and sticker (used to help those droplets stick to plant material long-enough to work). But spreaders and stickers are generally just soaps, detergents, acids and bases. They all kill soft-bodied insects and damage your plants. When you grab a bit of dish soap, blend an onion or a hot pepper and spray your plants you are causing your plant to react permanently to a chemical attack. It washes off the natural waxes on the leaves protecting the plant from UV or …get this….insects. Once it washes off, the plant is more easily attacked by aphids and the smell of both what you sprayed and the plants natural chemical reaction to the spray will ward-off natural predators. So you better make a big batch of that home remedy because it’ll be the only thing that works for you for the rest of the season, and your plant will suffer.
So keep it simple: Look at the aphids closely. You’ll probably never see an aphid egg, so anything that looks like an egg mass or a little grain or rice is an egg from something else. Chances are any other thing you see near the aphids is a predator. If that’s the case (you see aphids and anything else), leave them be. The predators eventually win. If you can’t wait, spray them off with simple water. If you have a protected area or a low threshold for aphids, buy and apply Aphidoletes from the closest supplier that doesn’t store them cold or for long periods. Your plants will thank you.
For a more in-depth or comprehensive look at aphids, read this: Everything you need to know about Aphids
Read more: Why I put aphids in my garden.
Read more: Grow Hard
Read more: Hardening off and leaning out.
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Great article , had no idea that the soap I was using was harming the plant . Also , no buying of ladybugs .
I will continue to wash off the aphids . Thank you for the information .
How can I get rid of the aphids on my indoor kale and swiss chard plants?
I have Virginia creepers and I believe I have a white fly infestation versus aphids. What’s the best thing to use for them.? One year I did use ladybugs that I swear it helped a lot
Ladybugs would help with the aphids, but don’t do much against whitefly. Your best bet, Preventatively would be Encarsia Formosa. It is a tiny wasp that only parasitizes whitefly. It that’s only for some species. Another option is a type of ladybug (but all black) that only eats whitefly and many species of whitefly: Delphastus catalinae.
Washing off aphids is a temporary “solution” although they will just climb back onto the plant the next day as if nothing ever happened. Tried it with my pepper plants, and leaving aphids alone is a surefire way to decimate your plants if predatory insects aren’t present. You see them on your plants simply because predators aren’t there to eat them.
Thanks for the info. I need Aphid killers. Pecan trees are flooded with Aphids. Trees, cars, buildings, ground, fences all sticky. Even dogs must be washed each time they are out. It has never been like this. No Ladybugs or Lacewings have shown up this year. These are 100 ft trees. Must do something.
Aphidoletes aphidimyza are the bio control used in pecans. You can get the best ones (North American) from evergreengrowerssupply.com
Im hoping you can advise as I’ve been told so have a problem with aphids although I have never seen them as illustrated in your article.. I have a beautiful old massive tulip tree on my property that during the months of May – July gets sappy. It’s a big issue and we can’t park near the tree nor can we enjoy our garden and my potted plants on our deck are affected by the sap. Any suggestions welcomed! Thank you!! 😀
I’m sorry. I replied to this earlier, but it didn’t go through. I’ll try again…
On Tulip trees and similarly on Linden trees this is an ongoing problem around the globe. The particular aphids in question naturally have an explosion in population at the same time each year. They honeydew is always produced, and during dry spells can be particularly disruptive. Municipalities and homeowners do the same thing to help control it: Rinse the honeydew with water (it’s water soluble) and try to prevent it.
Prevention is done with a single release of Aphidoletes aphidimyza near the tree about the time the aphids show up each year. (You have to look because their population is there long before most people notice the honeydew). Or you can release a few preventative releases in the weeks leading up to it. In most places in the Northern Hemisphere, these releases should be no earlier than the last week of April. (A little later if late frosts are a possibility.) The aphidoletes will lay eggs amongst the aphids and their larvae will feed on them. A larva lasts one week and then drops to the ground to pupate. Pupation can last two weeks and then the process starts over again. So a preventative release early saves you money. And if there are no pesticides used below the tree then you can get a cycling occur.
Single trees are tough because the predators have trouble catching up (with is the intention of nature..these big booms in aphids are meant to feed the ladybugs which are impactful later in the season.) Ideally, you have a diverse area with many aphid species and the aphidoletes can grow to great numbers ahead of the Tulip tree infestation. The timing requires some practice.
I hope that helps. I also have an article about releasing Aphidoletes in hanging baskets around the City of Victoria. This is also to establish Aphidoletes around the city ahead of the boulevard trees becoming infested.
This information is most helpful. I’m hoping for some advice. I have a hydroponic lettuce garden in my basement. It’s been very successful and I haven’t needed to buy greens in years. This past fall I made the mistake of bringing some peppers in to over-winter the plants. Green and winged aphids found the hydroponic plants and now I’m really struggling to control them. Given they’re indoors I can’t really hose the NFT system down. Also, I’m not sure releasing another (predatory) insect in my house will make me popular with my partner.
You noted a larvae and a fungal solution. Are either of these methods practical and safe to do in one’s house? If so where does one find them?
Thanks for reading and asking this question. You are up against it with hydroponic lettuce – it’s a great endeavor, but pests are most problematic. While I prefer all natural methods, I would not limit myself to them in your immediate situation. But indeed, I’d try the biocontrols first. Biocontrols are almost always perfectly safe, but what you can use depends on what’s available in your country. Many times these can not cross borders.
In what country do you live? In most developed countries you should be able to get Aphidoletes (a midge) and Aphidius (a parasitoid wasp). You may also be able to get various lacewing larvae. Most fungal options have commercial names, but generally they are species of Beauvaria.
As I mentioned, in your case I’d even explore things like neem oil or other “natural pesticides.” Only because irradiation will have to be your goal. In other gardens, small aphid populations can remain in check, but with indoor lettuce, you’ll have no help from the outside predators.
I hope this helps. Good luck!
Greetings from Missouri! I grow milkweed to attract monarch butterflies and collect their eggs to protect them from parasitic wasps. Then I raise & release them. Every year the aphids are getting worse, decimating the milkweed. Do you know if lacewing will eat or parasitize the monarch eggs I’m trying to protect? Thanks!
Hi. It is very likely that most predators will feed on the eggs. I wouldn’t risk it.
Aphids are difficult on milkweed because pests that feed on milkweed become toxic (if they survive). So aphids on milkweed (like monarchs) are protected from some predators.
The good news is aphid populations exploding are used to feed predators. So, there is bound to be native predators or parasitoids showing up.
My neighbour has tall poplar trees that have aphids every year. They rain down crap all over my car and every other surface, that I have to park on the street if I want to avoid the daily shower. Is there anything I can do since I can reach the trees as they are too high? Just thought I would ask.
Absolutely! It’s a well-known problem. Many municipalities have to control the same aphid-honeydew-rain on boulevard trees every year. They release the midge “Aphidoletes aphidimyza” every year. You (or your neighbour can do the same.
To make it cost effective, we typically wait until aphids are present then release 250 or 1000 per tree (big or small). In three weeks those populations increase 20 times, on average.
Or if you have aphids elsewhere, release the smallest amount now and they’ll migrate to the poplars.
The only thing to keep in mind: the midge’s larvae eat aphids then drop to the ground to pupate before repeating the life cycle. No pesticides can be used on the ground below the poplars.
This is the first year I noticed hundreds, if not thousands, of aphids on my rose of Sharon. What’s me best defense?
If it is an unusual occurrence it is best to blast off as many as you can with plain water, right away.
If you are keen, it’s worth looking to see if any are parasitized or if there are little white eggs or any predator larvae near by.
If there are, you can get away with rinsing some off and leaving it.
Additionally, you should release one small container of Aphidoletes aphidimyza. It’s a predatory midge of aphids and will quickly spread out adding to the aphid predation.