Gardeners have been battling aphids since the dawn of farming. These soft-bodied plant lice are one of the most prolific, damaging, and annoying pests to inhabit a garden. You treat them, knock them off, eradicate them from your plants, but somehow they return – so why do aphids keep coming back?
Aphids only live for about a month but during that time, they are constantly reproducing. For every one aphid, you can expect up to 100 more to take it’s place. The primary reasons aphids keep coming back is because of their constant reproduction, ability to hide, and ability to move to new plants.
Controlling pests, especially aphids, is not a once-and-done deal. Keep reading to find out the 7 reasons why they keep coming back, as well as some ways you can try to repel them!
1. Aphids Constantly Reproduce
As you stand out and admire the beautiful plants growing in your garden you see crimson tomatoes ripe for the picking, your potato plants are tall and strong, beans and peas tease you with plump pods of deliciousness, and your cucumbers are shriveled and covered with tiny green dots.
(Record scratch) Wait, what…?
Those darn aphids you treated a few weeks ago are back with a vengeance and wreaking mayhem on your precious vegetables once again. Gritting your teeth you set about treating them yet again, and you wonder why aphids keep coming back, and how can you prevent them from ever coming back again.
Aphids are so prolific that if they were to reproduce unchecked, under perfect conditions, they could create billions of aphids in a single garden season. When you are working to get rid of these pests, you will most likely have to treat them again and again.
The thing about aphids is you have to take care of them before a full-blown infestation happens. Once aphids have several generations and have spread from plant to plant, it will be much harder to get them under control.
Aphids have been around much longer than humans and they have developed some sneaky ways to survive whatever we throw at them. Here are several reasons why aphids return after you treat them.
Average Aphid Lifespan
The average lifespan of an aphid is between two to five weeks, much longer than the average mayfly which only lives about 24 hours, but during that time, aphids can create several new generations.
Chances are, the aphids you see on your plants without a magnifying glass are the adults that may not have long to live anyway. So when you’re treating them, you could be missing the nymphs or eggs. Most natural treatments, like neem oil and soap solutions, only work while they are wet.
This leaves the babies and eggs holding the reproduction torch. They can quickly reestablish a hearty colony of aphids, leaving you frustrated and having to spray them yet again to keep your plants alive.
2. Aphids Are Born Pregnant
That sounds like something from a scary science fiction book, but it’s true. These plant lice can reproduce without both sexes. Females can birth more females who are in turn already pregnant when they are born.
This asexual reproduction creates clones of the mother and is one of the reasons aphid infestations seem to happen overnight. Aphids can give birth to new, live, clones of themselves every couple of hours.
These bugs also don’t have to wait for eggs to hatch because these female clones are born alive, and ready to eat, which damages your plants. A single female can birth about 100 more, live, aphid nymphs during its lifetime.
Then in as little as seven days, those are ready to give live birth to another 100 offspring. As you can see, they are reproducing machines that can quickly overwhelm otherwise healthy plants in a very short period.
Aphids can give birth to new, live, clones of themselves every couple of hours!
You could do the math pretty quickly and see that one generation of aphids can create…let’s see, carry the one, and you get… a whole ton of new aphids ready to devour your garden!
3. Aphids Eggs Are Still In Your Garden From The Previous Season
The lifespan of an aphid is pretty complicated. Females can quickly start their infestation by giving birth to live clones of themselves. This way they can create an exponential population explosion, but they can also lay eggs.
When a female aphid lays eggs, they can contain both males and females. It’s all very complicated as well as convoluted, but as you can see, that’s why they can be so prolific, and difficult to completely get rid of them.
As the season warms up, some of the eggs start creating male aphids. Though females can reproduce by themselves, they need the males to keep the species going after winter.
When males and females mate, they create eggs that can overwinter which gives rise to a new population of aphids in the spring. And the cycle continues.
These females, plump with winter eggs, try to lay them on perennial plants that will come back after winter so that like Lazarus, the aphids rise from the “dead”. That’s just another way they continue to come back after fighting them.
4. Aphids Have A Higher Chance Of reproducing In Early Spring
Not only do aphids have the creepy ability to give live birth to already pregnant clones, but they can create eggs that can morph into males. If you thought that was the extent of their reproduction arsenal, get ready for another crazy evolution.
According to the Missouri Department of Conservation, aphid eggs that hatch after winter are all females that can reproduce asexually. These live-born offspring are exact clones of the mother aphid. Later in the season aphids are born with wings in male and female form which then lay eggs that can overwinter until next spring.
During the mid to later time of the growing season, when a plant is becoming too crowded to sustain the huge colony of aphids, its hormones start to create winged female aphids. These mighty morphing aphids then fly to new plants to start the cycle all over again.
So there are now flying females that are hopping from plant to plant, dropping new clones of themselves who can then start even more clones, but as autumn approaches, the winged females then start to produce more males; these also have wings.
When the boy aphid and the girl aphid get together, as we have seen, they create super eggs that can stand up to the harsh, cold winter. These are some truly busy, astonishing, hard-to-control pests!
5. Other Insects Are Bringing Aphids In
Some scientists have observed a behavior in aphids that help them survive better while moving from one plant to another. When an adult aphid falls off a plant and gets blown off by the wind, water, or other reasons, the smaller, weaker, slower aphids can jump onto the back of the adult as it scurries to a new plant.
Whenever adult aphids detach from a plant, the babies that have fallen off will try to climb onto the bigger bugs. Aphids are already quite small, but the nymphs are almost impossible to see with the naked eye. If they fall off their shelter, they may not make it back onto a plant before they expire.
A small pebble is like a mountain to the baby aphids, and the next plant could look like it’s in the next state. Nymphs are slower and weaker, and they could even starve before they make it to their next meal.
To solve this problem, they will try to hitch a ride on the bigger, faster adults. As we have seen, it only takes one aphid on a plant to create an infestation that can completely ruin it.
6. Aphids Survive By Moving To New Plants
It doesn’t take long for aphids to overrun a plant and shrivel it up into a papery shell. When the original host plant can no longer sustain a massive population of aphids, some move on to new plants.
They can do this by sprouting wings and flying away, or they can simply drop off and climb to another plant that will sustain a new colony. Since they are so small and can hide in tiny places, you may notice the infested plant, treat it, and think you’ve done the job.
Fast forward another week or two and suddenly a new plant in your garden is looking awful and you see the dreaded specks moving slowly on the stem and under the leaves. Now you have to treat these pests yet again because they moved away before you were able to get rid of the original colony!
7. Aphids Are Using Your Garden As A Hideout
We are learning more and more about aphids, which hopefully will give us more tools to deal with this garden menace!
Another evolutionary trait we have recently discovered is that some aphids may be able to sense when predators are approaching. They can then go into hiding to protect themselves.
Aphids don’t only have to worry about ladybugs, lacewing larvae, hoverflies, and other insect predators, but sometimes they get consumed by accident. Grazing animals like deer, cattle, goats, and sheep can accidentally eat aphids while they eat the plants that aphids are inhabiting.
It seems that some aphids have developed the ability to detect warm-blooded mammals. It may be a trait similar to mosquitoes and ticks which can detect carbon dioxide in the air which is a byproduct of mammal respiration.
This means that aphids may be able to detect when we are coming to remove them from our precious veggies and ornamental plants. Surely all of them can’t hide in the same place, and maybe they can’t move as fast as some so when we treat the visual aphids, we could be lulled into a false sense of completion.
We have sprayed the visual aphids and feel good, only to find them back again in a few days because some were able to detect the danger coming and hid away. Once the coast was clear, they came out of their hiding holes and began their accelerated feeding and reproduction schedule again.
Aphids can also hide in tiny cracks, crevices, and nooks of plants. The tiny nymphs can get into even smaller places.
Some plants offer almost unlimited hiding places such as broccoli, cabbage, lettuce, and other leafy vegetables. One way to combat hiding aphids is to continually inspect your plants. Look closely at your plants on the undersides of leaves, around new growth, or in the small crevices where insects can hide out.
Doing this every couple of days will help to notice anything out of the ordinary, and maybe be able to stop aphids before they can create a population explosion. A few aphids are easier to treat than millions.
How To Keep Aphids From Coming Back To Your Garden
Now you know why aphids continue to come back after you take care of them. The next question to answer is, “What, if anything, can be done to prevent aphids in the first place?”
When it comes to insect pests, there are very few, if any steps to take to completely, 100% prevent destructive bugs. But we have some ways that will drastically reduce the probability of an aphid infestation.
Maybe you can’t get rid of them completely or prevent them from coming along at all, but with the right steps, you will be able to keep them from becoming a problem.
Keep Your Plants Healthy
The presence of aphids can be an indicator of poor plant health. Much like mammalian predators who seek out the weak and injured in the wild, pest insects are often attracted to plants that aren’t doing their best. Healthy vigorous plants are also able to fight off moderate infestations of insects like aphids, so do your best to keep them strong and healthy.
Plants that are suffering from a drought, are over-fertilized, or otherwise already starting to fail will often attract aphids looking for an easy meal. Plants that are wilted from lack of water have a more attractive, concentrated sap that aphids will flock to. The concentrated sap will be sweeter and have more nutrients than aphids want.
Be sure to regularly water your plants in times of need. While you are watering them, if you see aphids, you can use the hose to spray them off. This will have to be done several times to make sure you have gotten them all, but it’s one way to prevent them from overwhelming your garden.
We all know fertilizer is great for plants, unfortunately over-fertilizing your plants—especially with a high nitrogen content—can attract pests like aphids. You can still add food for your plants, especially if they need it, just look for all-natural types and slow-release plant foods.
Mulching your plants and even your garden plants helps in so many ways. It helps to retain valuable moisture so you don’t have to water as much, it helps to prevent weeds (another way aphids can reach your vegetation) and it creates another barrier that crawling aphids have to cross to get to your plants.
Planting To Repel Aphids
Most garden pests start around the perimeter of your garden or flower beds and work their way into the middle. There are a lot of plants that work to repel pests, so go ahead and put up a natural perimeter barrier of repellant plants around your garden.
Many plants have scents that aphids and other insects hate, while other plants may attract aphid predators. Planting these around the outside edge of your garden will help to keep infestations from happening if it’s done before aphids are a problem.
Here is a list of plants that repel aphids:
- Onions and others from this family (chives, leeks, scallions, etc.)
- Fragrant herbs such as (dill, fennel, basil, parsley, cilantro, oregano, rosemary, mint, coriander, thyme, marjoram,
Planting some of these plants around your garden will help to prevent aphids from getting to prized plants. Some can even be added to the garden as companion plants.
Take basil, for example, it pairs well with tomatoes and peppers to both repel pests, invite predatory insects, and improve the taste of both vegetables.
Onions work well with plants from the cabbage family such as kale, (which can offer plenty of places for aphids to hide) cabbage, brussels sprouts, and broccoli.
To ramp up the aphid deterring abilities of these plants, plant a perimeter around your garden of something aphids don’t like, then companion plant garlic, herbs, and onions to show the bugs they aren’t invited.
You read our full list of scents that aphids hate here to learn more about using them!
Grow Some Aphid Trap Plants
Though some of the most famous trap plants might be the venus flytrap and pitcher plant, these are tropical plants that need a lot of water and humidity. The trap plants we are talking about are plants you let aphids munch on so that they don’t get into your vegetables or ornamental garden.
The United States EPA informs us that aphids like to eat trap crops like calendula and nasturtiums more than your vegetables so you can use those plants to keep aphids away. Also, plant flowers attract beneficial bugs that eat aphids.
These plants are like candy to aphids. Just like someone who would rather eat sweets instead of nutritious vegetables, aphids will hit these trap plants first!
These plants are usually easy to grow, cheap, and grow fast so it won’t be so painful to cut them down or uproot them when getting rid of the aphids.
Here is a list of trap plants you can set up in your garden to attract aphids, then get rid of those nasty buggers:
- Nicotiana-or flowering tobacco plants
What you do is allow the aphids to establish themselves on these trap plants, then cut down, or pull them up and dispose of them, aphids and all. You could compost these plants but you will have to make sure the temperature in the compost is hot enough to “cook” the bugs.
This fascinating paper published in PLoS Biology by several brilliant researchers found that a specific aphid species, tuscan aphids, has a specific gene that can be affected by high heat.
Specifically, they found that these exposing these aphids to 95 degree Fahrenheit temperature for a minimum of 4-hours resulted in “sterilizing” the aphids, meaning they couldn’t reproduce.
While the high heat didn’t eliminate them, it may be a wonderful solution for your garden aphids regardless of species!
So, your process could look like this: Trap plant –> compost –> bask in the sunlight.
The compost pile should be far enough away from the garden so the aphids can run back, regardless if they can reproduce.
An easier way is to seal the aphids and infected plants in plastic bags and dispose of them in the trash. You could also drop the entire plant in a bucket of soapy water. The soap will break down the outer covering of the aphids and keep them from floating to the top and scurrying away.
Be sure when you are removing the plants that aphids don’t drop off and run away. As we know, one single aphid can create generations of clones in a short time.
Essential Oils Are Effective Aphids Deterrents
If you don’t want to go to all the trouble of planting more vegetation in and around your property, you can use essential oils to prevent aphids.
Just like the strong-smelling herbs that keep aphids away, the same principle works with essential oils. All you have to do is add a few drops of concentrated essential oils into a spray bottle of water and either spray the aphids directly or spray the plants you want to keep pests away from.
These essential oils have the scents that aphids detest:
For a super aphid repelling and eliminating essential oil potion add two to three drops of clove, rosemary, mint, and thyme oil each to your spray bottle. Shake vigorously, then spray the aphids directly or where you don’t want them to go.
You’ll have to spray the plants periodically because the strong smell will fade away after a few days or after a soaking rain. The essential oil mixture won’t harm your greenery so long as you don’t use the concentrate directly onto the plants or create a solution that is too strong.
Diatomaceous Earth Can Get Rid Of Aphids
Another natural, safe for humans and food preventative and eliminator is using diatomaceous earth. This powder is fossilized microscopic sea creatures that work by creating tiny cuts on insects that walk through it.
The tiny cuts cause the insects to fatally dehydrate. It works on aphids and many other common garden pests. You can dust the insects you see, or leave a barrier around plants you don’t want to be infested with these pests.
Diatomaceous earth is safe for humans and animals, but you may want to use a dust mask, or particle filter mask (N-95) when spreading it because some brands may contain small traces of silica which can irritate the lungs. If you are spreading it around fruits and vegetables you should look for food-grade diatomaceous earth such as HARRIS Diatomaceous Earth Food Grade brand.
As with essential oils, you will have to reapply diatomaceous earth after rain or after several days as it will lose its effectiveness the damper it becomes.
Invite Some Ladybugs Into The Garden
As well as hoverflies, lacewings, predatory wasps, spiders, birds, etc. The best way to deal with aphids is with their natural predators. All the aforementioned creatures will feast on aphids so you don’t have to do much to treat them.
To invite these aphid predators into your yard you need to make your area inviting to them. Certain plants will attract the adult forms of hoverflies, ladybugs—or lady beetles—and lacewings, whose larvae will keep aphids populations from getting large enough to damage your crops
Plants that attract these predatory insects are queen Anne’s lace, dill, yarrow, alliums, verbena, lavender, asters, sedum, coreopsis, and marigolds. Plant these in and around your yard to bring in nature’s aphid regulators.
Or, heck, you can just buy NaturesGoodGuys – Live Ladybugs and introduce them to your garden! You should still put ladybug friendly plants in your garden to keep them around.
One thing to think about when inviting beneficial insects into your garden, once you let them patrol your vegetation, you’ll have to be extra diligent not to use any pesticides or products that will destroy them. Bring in the good bugs and let them do their jobs.
So now you know why aphids keep coming back to your gardens. They are extremely prolific, they can hide away and morph from one type of aphid to another, the eggs can withstand the winter and they can move from plant to plant.
By employing one or more of the mentioned prevention methods such as trapping plants, diatomaceous earth, essential oils, or attracting beneficial predators you can keep aphids at bay. Or at the very least, you can keep their numbers in check enough that they don’t permanently damage your plants.
Li, Jinjin, et al. “Defense of pyrethrum flowers: repelling herbivores and recruiting carnivores by producing aphid alarm pheromone.” New Phytologist 223.3 (2019): 1607-1620.
Goggin, Fiona L. “Plant–aphid interactions: molecular and ecological perspectives.” Current opinion in plant biology 10.4 (2007): 399-408.
Pickett, J. A., et al. “Plant stress signaling: understanding and exploiting plant–plant interactions.” Biochemical Society Transactions 31.1 (2003): 123-127.
Nottingham, Stephen F., and J. I. M. Hardie. “Flight behaviour of the black bean aphid, Aphis fabae, and the cabbage aphid, Brevicoryne brassicae, in host and non‐host plant odour.” Physiological Entomology 18.4 (1993): 389-394.Dunbar, H. E., Wilson, A. C. C.,
Ferguson, N. R., & Moran, N. A. (2007). Aphid thermal tolerance is governed by a point mutation in bacterial symbionts. PLoS biology, 5(5), e96.