Aphids on your milkweed plants can be a cause of concern, but more so if you have monarch butterflies on them. But do aphids eat monarch eggs or harm them in any way? Well, not directly, but indirectly they do cause harm.
Growing milkweed plants in your butterfly garden is a great way to attract beautiful monarch butterflies to your home.
However, these endangered butterflies aren’t the only insects you’ll be attracting. Milkweed also attracts oleander aphids.
They are so brightly colored that you can easily spot a large infestation of these tiny yellow bugs on your milkweed plants. While the aphids won’t destroy or eat monarch butterflies’ eggs, they can harm the larvae indirectly. Let’s understand how.
What Are Oleander Aphids?
Let’s begin with learning more about this species of aphids. These bright yellow insects easily stand out from the other aphid species due to their color.
In fact, their bright color is an indicator to potential pests that they contain toxins – a defense mechanism common in many bugs.
This bug isn’t native to the US – it originated in the Mediterranean region, just like its primary host – the oleander plant.
It later ended up in North America through these very oleander plants and eventually grew to become common here as well.
Milkweed is pretty much as attractive to them as oleander, which is why they are also called “milkweed aphids.”
If you have milkweed plants in your garden, there’s a high chance that you may have to deal with an aphid infestation at some point.
Do They Harm Monarchs?
Moving on to why you’re here, let’s see how these tiny little milkweed bugs can harm monarchs.
First of all, aphids hog milkweed plants. Aphids infest in large numbers because of their unique asexual reproduction, covering entire areas of the plant with their bright yellow bodies.
Well, you might say that still doesn’t answer how aphids can harm monarchs. The answer is that they do nothing direct – they don’t bite, and they don’t feed on butterfly eggs.
They are completely herbivorous and only feed on plant sap.
However, this sap-sucking is what harms monarchs. These pests drain nutrients from the sole host of the monarchs, i.e., the milkweed plant.
A heavy aphid infestation can completely defoliate the plant, leaving the poor monarch butterfly nowhere to go. Neither do their caterpillars get nutrition from feeding on the plant’s leaves.
The presence of an aphid army also draws natural aphid predators like ladybugs and lacewings near the plant.
While these predators are otherwise beneficial, they also eat up monarch eggs. Hence, while the aphids won’t eat monarch eggs, they can attract predators who will.
Why Are They So Hard To Get Rid Of?
Dealing with an aphid infestation on your milkweeds is frustrating due to their sheer numbers and because you can’t use the normal methods of aphid control with monarchs in the picture.
Using pesticides or insecticidal soap to kill the aphids might destroy the monarch eggs and larvae.
Beneficial insects like lacewings and syrphid flies kept for controlling aphids can feed on monarch eggs, causing more harm than good.
Even if monarch butterflies haven’t laid eggs yet, most aphid predators don’t touch oleander aphids. These guys extract cardenolide toxins from milkweed, which turns them toxic and protects them from predators.
How To Control Their Population?
While its getting rid of aphids on your milkweed plants is hard, it’s not impossible. You can remove them by hand, drown them in water, apply soap water, vacuum them off, and there are many other things to do. Let’s talk about them.
Manually Remove Them
Although this might sound a bit messy, squishing the aphids with your fingers is the most effective way to eliminate them.
You can then wash away the crushed pests with a stream of water. However, ensure you don’t mistake monarch eggs for aphids or aphid eggs.
While aphid and monarch eggs are both ovoid, monarch eggs are white or off-white. Female aphids, on the other hand, mostly lay yellow, orange, or black eggs.
Drown Them in a Stream of Water
Another way to kill aphids easily is to hose them down with a stream of water. The water would wash them off your plant, and the pests would also die from drowning.
Alternatively, you may take water in a bowl and carefully turn different parts of the plant to submerge them in the water and kill them.
Use rubbing alcohol
Isopropyl alcohol, also known as rubbing alcohol, can kill aphids on contact.
However, you will have to be extra careful when spraying it, as rubbing alcohol can also kill monarch caterpillars and destroy their eggs.
If you have dealt with pests in your garden or your houseplants, you probably know that soapy water is an excellent insecticide against many pests.
Spray the aphids with a solution of water and dishwashing liquid to kill them.
As with rubbing alcohol, you’ll have to avoid harming the monarch larvae, ladybug larvae, lacewing larvae, or syrphid fly larvae.
Use a Brush or Vacuum
Don’t want to use chemicals? You may use a vacuum cleaner to remove the pests. Just make sure the suction power isn’t too high, as it can cause the leaves to tear apart or get sucked in.
It’s best to use a small handheld vacuum cleaner, a keyboard vacuum cleaner, or a vacuum cleaner with a micro attachment.
You may also brush the pests off your plant using a detailed brush. It will help you remove aphids from areas that might otherwise be hard to reach.
Plant Aphid Repellent Plants
This natural remedy will help you control the populations of aphids while increasing diversity in your garden.
Certain plants, such as marigold and onion, repel aphids naturally. You can introduce some of these repellant plants into your butterfly garden and plant them next to the milkweed plants.
Frequently asked questions
What eats monarch butterfly eggs?
Various predators, like spiders, wasps, ants, ladybugs, etc., feed on monarch butterfly eggs. Most of them target these butterflies at the larval stage too.
You should try to keep these predator insects away from any milkweed plant on which the monarchs have laid eggs.
Will monarchs lay eggs on milkweed with aphids?
Yes, the monarchs will still lay eggs on a milkweed plant infested with aphids. The infestation won’t deter them in any way.
While this is a good thing, you need to get rid of the aphids immediately, as they can indirectly harm the monarchs by damaging the milkweed.
Do aphids eat baby monarch caterpillars?
No, aphids only feed on plant matter, mostly the sap from the leaves. They do not eat baby monarch caterpillars. However, other predators like spiders, ants, and birds who eat monarch caterpillars might get attracted by the presence of aphids and end up feeding on the caterpillars.
Do aphids harm monarch chrysalis?
Aphids don’t harm monarch chrysalis directly. However, they can deprive them of nutrients by draining the sap of the host plant or even killing it.
Hence, although aphids don’t attack monarch butterflies in any life stage, you should still keep your milkweed plants free of those pests.
Aphids are extremely common pests, and there’s a good chance that they might show up in your pollinator garden.
Take the necessary steps to eliminate them and protect your milkweed plants. Remember not to use pesticides or other solutions.
They might result in collateral damage, such as destroying monarch eggs or killing other beneficial insects. Thank you for reading!
Over the years, our readers have sent us several emails on this topic. Please go through them below.
Letter 1 – Maple Aphid we presume
Subject: Unknown Bug on maple leaves
Location: Springfield, NJ
March 3, 2017 9:18 pm
A large number of these pinhead sized bugs hatched on my bonsai maple buds and leaves on a warm February week.
This is great information and very interesting.
Letter 2 – Mexican Aphids
hi I am from mexico and I have faund many insects in my garden that I cant identify so if you can help me I will be thankfull.
Did you attach photos? They did not arrive. Where in Mexico?
well first i¨am fome mexico city the capital y will send you the fotos now.
Hi again Daniel,
This image is of a species of Aphid, from the family Aphididae. They are pests that infest many types of plants. When numerous, they can be very injurious, especially to young tender shoots. They suck the juices from the plants and are also capable of tranmitting viruses to your plants.
Letter 3 – Milkweed Aphid
Subject: Yellow Bug
Location: Detroit, MI
October 30, 2013 4:05 pm
Found these on my back porch today and I have no idea what they are. I tend to have a lot of lady bugs in the backyard but this doesn’t look like a lady bug. This was taken in Detroit, MI. Today (October 30th). And there was a bunch of them in various sizes. Some super tiny like the tip of a pen and others about 2-3 times that size…so bigger than the babies but still small.
This is an Aphid. If you have plenty of Lady Beetles, they must have a ready food supply, and they prey upon Aphids. We believe your Aphid is a Milkweed Aphid.
Letter 4 – Milkweed Aphids
Bug on my Gay Butterflies
Location: Central Texas
June 1, 2011 7:22 pm
I went out to water our flowers this evening and noticed these bugs on my Gay Butterflies. As you can see from the attached photo, there are plenty of them. I have not been able to identify them from my searches and would like to identify if they are harmful to our flowers or if they will be okay to leave alone. The bugs have 6 legs, 2 antlers/feelers, and what looks like two feelers or antlers on their back behind their back legs. We have a lot of lowers in the flower bed (26 to be exact) and the gay butterflies are the only thing that seems to attract these critters.
You definitely have Aphids, and we have never heard of a plant called a Gay Butterfly, but it appears to be a milkweed, which would be strong evidence that your Aphids are Milkweed Aphids, Aphis asclepiadis. They do match the images posted to BugGuide. Using pesticides may compromise the butterflies you are hoping will be attracted by the plant. We would suggest a strong spray of water from the hose to remove the Milkweed Aphids.