Aphids are small but can be mighty pests in gardens. You may notice these little specks with legs on your garden vegetables and fruits and wonder ‘why are you here?!’ Besides the obvious answer of food, there are several other reasons why aphids are in your garden.
Some of the most common reasons why you have aphids in your garden include:
- Looking for food
- Protected by ants
- Time of the year
- High nitrogen content
- Pesticide & insecticide use – eliminates natural predators
- Region – most diverse in temperate zones
Below we’ll go over the 6 reasons why aphids are strolling through your garden and how you can remove these annoying pests as in-depth as we can. Then, we’ll get into the nitty gritty of solving these issues. Let’s get to it!
Aphids Are Looking For Food In Your Garden
Aphids are just like any other living creature – they look for food, water, and shelter to survive. Unfortunately, your garden provides them with all three of these necessities in one place!
According to the University of Wisconsin-Madison, there are over 5,000 species of aphids worldwide. With such diversity in the species comes diversity in food preferences as well.
Certain garden plants are more likely to attract aphids than others. Some aphids are attracted to very specific plants while others are not so picky with their food and will eat from just about any garden plant.
Some of the garden plants that are particularly attractive to aphids include:
- Legumes – beans, peas, lentils
- Mustard plants – broccoli, cabbage, cauliflower, turnip, kale, arugula
- Solanaceae family – tomatoes, potatoes, peppers, eggplant
- Cucurbits – watermelon, cucumber
- Spinach and lettuce
- Stone fruits – plums, cherries
Unfortunately, this list includes many of the staple plants found in your average garden. The good news is that aphids cause minimal damage to plants in most instances. You can view our full list of vegetables aphids or fruits that ahpids are most likely to snack on if you’d like to learn more of the specifics!
Severe damage only comes from a major infestation. These types of infestations only happen under specific situations. A perfect storm, if you will.
If you’re worried about aphids, you can plant certain things in your garden that repels aphids. According to the University of Arizona, the four plants that aphids usually leave alone include:
Pretty much any plant that has a particularly strong odor will be less attractive to aphids. If you want to know what flowers aphids are attracted to so you don’t plant those by accident, you can read our full list of the 9 flowers that aphids love!
Ants Are Protecting Aphids In Your Garden
Aphids are prey to a variety of predators that dwell in your garden. They’re an easy target as they are soft-bodied and have almost no defense against predators.
However, some aphids have ant protectors watching out for them that will harass predators away or even eliminate the predators.
If you notice a large population of ants in your garden, it’s a good indicator that you also have a large aphid population.
So, why are ants so protective of aphids?
It all has to do with a sweet, sugar-filled substance that aphids excrete called honeydew. This sugary, sticky substance is eaten by ants. Since aphids provide ants with a food source, ants provide aphids with some muscle in the garden.
Some of the natural enemies of aphids like parasitoid wasps and lady beetles can be driven off by ants, giving aphids free reign over the plants in your garden.
One of the ways you can combat this is by managing the ants in your garden. Once the ants are taken care of, the natural predators of aphids will be able to do their thing and keep the aphid population in check.
Terro’s liquid ant killer bait stations can be set out around your garden to help eliminate ant populations. This product comes with 12 bait stations so you can be sure to cover all areas around your garden.
Aphid Populations Are Higher At Certain Times Of The Year
Have you ever noticed that certain bugs and animals are more prevalent at certain times of the year? We might notice spiders in the house more often in winter than summer, or see yellowjackets more in the fall than in spring.
Aphids have a schedule too, and knowing when their numbers are highest can give you a good idea of when to look for these pesky garden invaders.
Spring and fall are when aphid populations will be the highest in your garden. The main reason for this has to do with their lifecycle and migration patterns.
According to the University of Minnesota, female aphids will lay eggs in the fall that live through winter on plants and trees. In the spring, these eggs hatch and, once they mature, the females can reproduce without mating and give birth to live young.
In other words, spring is when aphids are just being born and colonies are rapidly expanding. An aphid can reach reproductive maturity in just over a week! Then those aphids begin producing live young and the cycle continues.
Aphid populations can explode in late spring when this cycle is reaching its peak.
Once peak populations are reached, some aphids will migrate off their host plant and find a different plant to chow down on.
For example, the Mealy plum aphid is a big fan of plums and prunes, but they vacate these plants in the summer and infest cattails and reeds instead. According to the University of California, rosy apple aphids and leaf curl, plum aphids perform similar migrations in the summer.
So, while aphids are off on their summer vacation on different plants, your garden plants have the opportunity to flourish. But keep in mind that not all aphids disperse in the summer.
After they are done vacationing on cattails and other plants, aphids will migrate back to their original host plant to begin the egg-laying process in the fall.
For gardeners, this isn’t a huge cause for alarm because most gardeners till their garden and destroy the leftover plants before winter hits. This will help destroy the eggs and lessen the aphid population in the spring.
If you don’t already do this, it might be a good time to start to help reduce future aphid colonies!
Aphids Are Attracted To Fertilizers Rich In Nitrogen
Well, aphids aren’t necessarily attracted to the fertilizer itself. But they are attracted to plants that are fertilized with high nitrogen contents.
Nitrogen is an essential element in many everyday fertilizers used for potting soil. There is typically some kind of balance between nitrogen, phosphorus, and potassium known as the N-P-K ratio.
You may see on the labels of fertilizers 10-10-10 or 10-5-10. This is calling out the ratio of nitrogen, phosphorus, and potassium.
According to Texas A&M University, most garden fertilizers will be a ratio of 10-20-10 or 12-24-12. In other words, double the phosphorus content compared to nitrogen and potassium.
The reason the nitrogen content is so important is that nitrogen is what aphids are looking for when they eat the sap of your garden plants. They need some sugar and other amino acids too, but nitrogen is what’s important in the diet of an aphid.
Aphids can tell when a plant has a higher nitrogen content just by taking a small sample of the sap.
An article in the Journal of Plant-Animal interactions found that aphids will feed for longer on plants that are rich in a nitrogen source such as fertilizer. Additionally, aphids settled more frequently on plants fertilized with high nitrogen content.
So, if you use a fertilizer with high nitrogen content, you are far more likely to attract and retain aphids in your garden than if you used a low-nitrogen fertilizer.
A fertilizer like Ultimate Fertilizer 10 lb Veg Garden Fertilizer would be a good choice. It is a 10-20-10 ratio and will cover up to 2,000 square feet.
Pesticides & Insecticides Eliminate Natural Aphid Predators
Nobody wants a bunch of pest insects destroying their garden plants before you even get a chance to harvest.
For this reason, some gardeners rely on pesticides and insecticides to keep their vegetables in good condition and to keep garden pests off their plants.
Unfortunately, for aphid damage, this can do more harm than good.
According to the University of California, most plants will survive light to medium aphid levels without taking too much damage. Large aphid populations might do some damage but they will quickly be controlled by a rising predator population.
However, when pesticides and insecticides are used, these chemicals also eliminate the natural predators of aphids like lady beetles, parasitic wasps, and spiders.
A field study published in Pest Management Science was done over three years to test the effects of an insecticide on aphids and aphid predators. What they found was that it varied depending on the specific chemical compound in the insecticide.
Some of them, such as the chemicals Fluvalinate and esfenvalerate highly affected ladybugs, while pirimicarb had little effect on ladybugs.
All in all, unless you know what chemicals affect specific species, you can’t know for sure what predators are affected by certain insecticides. Additionally, because aphids reproduce so quickly, they can become resistant to certain sprays within a short time.
It can be difficult to reach aphids with insecticides and pesticides once the population has established and gulls or leaf curl has already taken place.
This offers the aphids protection from sprays unless you turn over every leaf in your garden and apply the insecticides.
A better solution is to use your hose to spray the aphids off. This may not eliminate all of them, but it will help keep predator populations thriving so they can take care of your aphid problem naturally.
Aphids Are More Present In Temperate Zones
Another reason why you have aphids in your garden has to do with where you live! These pesky insects can be found all over the US, but they are more prevalent in certain areas.
Aphids are more common in areas that experience distinct changes in the seasons, known as temperate zones.
If you live in some of the more tropical states like Florida, California, and southern Texas, you probably will not have to deal with aphids as much as someone who lives in New York or Ohio.
Not only are aphid populations denser in temperate regions, but there’s also a larger diversity of species. This correlates to a couple of negative attributes for temperate zone gardeners:
- More diversity means more plants are affected: Because there is more variation in aphid species in temperate zones, a more diverse group of plants is going to be affected. There are melon aphids, woolly apple aphids, bean aphids, cabbage aphids, etc. in temperate zones. In other climates, you may only have melon aphids, for example, which affect citrus fruit.
- Diverse aphid populations mean diverse resistance: The more varied the species in a single area, the more varied their resistance is to certain insecticides and pesticides.
- More diversity means more predators are needed: Some predators like spiders are generalists and will eat whatever comes around. Others are specific to certain pests on certain plants. With more diversity comes the need for a more diverse group of predators.
Unfortunately, there’s nothing that can be done about the weather! BUT, knowing that aphids use winter to lay eggs comes with its advantages.
Gardeners can ensure a smaller aphid population in the spring by taking care of a few things in the fall:
- Destroy plants after harvest – this destroys the eggs if any are present
- If you have susceptible trees in your yard, spray these in the fall or early spring to eliminate aphid eggs.
Something like Natria Neem Oil Spray for Plants Pest Organic Disease Control works great for aphid eggs and is safe to apply to most plants (always read the directions on the label before applying).
- Provide habitat for overwintering predators – rocks, leaf piles, trees, etc.
How To Keep Aphids Out Of Your Garden
If you have an active aphid problem or you are worried about them infesting your garden, you may be wondering how to keep these pesky insects out of your garden?
There are a few different things you can do to keep aphids out of your garden.
The best practice is to implement more than one strategy to keep your aphid population in check and keep your garden plants happy and healthy.
If you’ve had aphids before and still do, take a look at our guide on the most common reasons why aphids keep coming back.
Inspect Plants Often and Early
Aphid eggs will start hatching in mid-to-late spring and populations will quickly swell from there. One of the best things you can do for your garden is to inspect your plants early and often.
You don’t want to wait until you are seeing signs of leaf curling or yellowing leaves. You want to catch the aphids before this happens and when populations are relatively low.
It’s recommended to inspect your plants at least twice a week. Be sure to flip leaves over and inspect the underside, as this is where aphids will often hide.
Once you start seeing aphids, you can use your garden hose to spray them off the leaves.
You can also use a solution of water with a few drops of dish soap to eliminate the aphids. Another option is to use a paper towel and physically wipe them off the leaves, but this can be tedious.
Use Distasteful Scents and Smells
Believe it or not, aphids have a sense of smell! They use this mainly to find food, but also to detect predators and identify their family members.
Using scents and smells that aphids dislike can discourage them from coming near certain vulnerable plants.
Some of the smells that aphids dislike include:
- Capsaicin (hot sauce)
- Neem oil
You can find a more in-depth look at the scents that aphids hate here. Using scents has its advantages and disadvantages. You must apply the scent often so that it remains strong and continues to repel the aphids.
The positive aspect is that it is a natural remedy that doesn’t use harsh chemicals with a bunch of words you can’t pronounce.
Manage Ants To Keep Aphids Out Of Your Garden
We touched on this a little bit earlier in the article but it’s worth repeating. Controlling the ant population in your garden can help lower the aphid population.
You can also use the ant population in your garden to gauge the aphid population. If you’re seeing a ton of ants climbing up and down your plants, you likely have a large aphid population that is being protected by the ants.
Using bait traps is a great way to control ants. Another option is to use scents and smells that both ants AND aphids dislike. Some of the overlapping scents include:
- Capsaicin (cayenne pepper)
Mighty Mint’s Plant Protection Peppermint Spray is an excellent choice to control both ants and aphids as the main ingredient is peppermint oil.
You can learn more in our full list of scents that ants hate here!
Encourage Natural Aphid Predators
Another way to keep aphids from sucking all the sap from your garden plants is to encourage predators to stick around.
Planting perennial flowers around your garden will encourage predators like wasps, bees, and certain spiders.
You can also hang up a ladybug house like Lulu Home Wooden Insect House. This can attract ladybugs, bees, butterflies, and a host of other beneficial insects that will help reduce your garden aphid population.
That’s All For Now!
Aphids may be small but they sure can be BIG pests in the garden. They can curl the leaves of your garden plants and turn them yellow. If their population is big enough they can do some serious damage to garden plants.
Most of the time, aphid populations are moderately sized and your plants will bounce back from their feeding.
You can keep aphids out of your garden by encouraging natural predators, using scents and smells they dislike and controlling the ant population in your garden.
However, the best way to keep aphids out of your garden is by inspecting your plants often and early in the season. Spray them off with a garden hose to remove them from your plants. Don’t forget to spray the underside of the leaves!
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Bilde, T., & Toft, S. (2008, July 07). The value of three cereal aphid species as food for a generalist predator. Physiological Entomology, 26(1), 58-68.
Nowak, H., Komor, E. How aphids decide what is good for them: experiments to test aphid feeding behavior on Tanacetum vulgare (L.) using different nitrogen regimes. Oecologia 163, 973–984 (2010).
Ragsdale, D. W., Landis, D. A., Brodeur, J., Heimpel, G. E., & Desneux, N. (2011, January). Ecology and Management of the Soybean Aphid in North America. Annual Review of Entomology, 56, 375-399.
Rutledge, C. E., O’Neil, R. J., Fox, T. B., & Landis, D. A. (2004, March 01). Soybean Aphid Predators and Their Use in Integrated Pest Management. Annals of the Entomological Society of America, 97(2), 240-248.