Yellow aphids can appear in large colonies and are often a terrifying sight as they devour milkweed plants. They are a non-native insect and they can multiply very quickly. However, they are not a direct threat to monarch caterpillars because they feed on the milkweed plant only. They can indirectly affect caterpillar health by depleting nutrients in their only host plant. Using systemic insecticides to get rid of aphids can actually be much more harmful to the monarch caterpillars than the aphids themselves.
What are oleander aphids?
The oleander aphid (Aphis nerii), sometimes called the milkweed aphid, is a common pest of milkweed plants. It is a non-native bug, most likely originating in the Mediterranean region where it's principal host plant, oleander, grows.
The Oleander aphid is a bright yellow insect with black legs, and stalks known as cornicles on the back of the abdomen.
Method One: Manual Removal
Although, time-consuming, the safest way to remove aphids is manually by squishing them between your fingers (use gloves to avoid staining your fingers) and then using a hose to dislodge them from the plant. Always check for monarch eggs and caterpillars before spraying because you could damage or dislodge them in the process as well.
It is best to catch the aphids before they become an aphid army, so even if there are just a few on the plant, remove immediately.
Method Two: "Contact Only"
This is a method recommended by Monarch Watch and was shared by Vic Jost @ Jost Greenhouses through Elliott Duemler at Taylor Creek Nursery. A mild solution of dish soap and water will also work.
• 1 part (e.g. 1 oz) Blue Dawn
• 1 part Isopropyl Alcohol
• 1 part white vinegar
• 128 parts (e.g. 1 gal) water
"Contact only" means that the insects have to have the mixture applied directly to their body for it to work.
*Use caution with this method because it will also kill monarch larvae if they come in contact with the solution. Rinse the plant when finished so you do not injure monarch larvae and other beneficial insects.
Method Three: Beneficial Insects
Beneficial insects are great for controlling numbers because they rarely harm monarch eggs, caterpillars, or adults and once introduced, they take no effort on your part! Once their food source is gone, they will generally leave your garden in search of food.
There are many species of beneficial insects. It is important to be able to identify these insects so you know which ones are on your side. Ladybugs, hover flies, lacewings, Aphidius wasps, and a few more types of beneficial insects devour aphids.
Monarch Joint Venture
Natural History of Orange County and nearby places.
8/1/2019 08:28:12 pm
A simpler method is a quick direct spray with a solution of Castile soap and water.
Lou Sipolt, Jr
7/22/2020 05:40:59 pm
What is Castile Soap?
7/29/2020 06:16:57 pm
Maybe Kirks Castile soap? But that’s a bar. I bet they make it in a liquid too. I just found milkweed aphids on all my milkweed and I went out there and handpick them but I don’t think they are all gone. I’m going to look into the Castile soap as my next move
8/8/2020 10:34:46 am
You can find Castile soap in a large bottle on the bottom shelf at Wal-Mart or Costco (probably elsewhere, but it is where I saw) I have some and will try this on my multitudes of aphids! We plucked about 12 monarch caterpillars from the plants and put them on non infested milkweed. Now I can safely spray with whatever will work.
9/6/2020 09:15:03 am
The best liquid Castile soap is Dr. Bronners. Once you are finished killing the aphids, you can use the soap in many ways...laundry, dishes, body...
Susan J Ahrens
2/21/2021 10:46:38 am
Castile soap is olive oil based soap.
10/28/2021 04:11:18 pm
its a natural soap. you can buy it in liquid. it works great in foaming soap pumps with 10% of this and 90% water. look for dr bronners
8/14/2020 01:04:51 pm
In a 1 gal spray jug of water Use 5 Tbls of Liquid castle soap & 1 tbls of baking soda, I just bought swamp milkweed plants. I haven’t even planted them in the ground yet & they already have the tiny orange bugs. This mixture does kill the bugs, but they came back so I did it again
11/7/2019 11:32:39 am
My milkweed have been completely taken over by the aphids. First I tried removing them with my hands, then ladybugs, now half of the plants are almost dead. I found so many caterpillars and plucked them up and have them safely separated and enclosed with plenty of food but don’t know if I should spray and leave a few plants that are doing well. The aphids are all the way down to the dirt on some plants.
11/10/2019 11:12:19 pm
Put maybe 2 tablespoons of dawn dish soap, more or less, into a normal sized spray bottle maybe 2/3 fullnof water and mix. Mist the plant and get aphids wet. Most will be dead in 36 hours. Repeat on the ones you missed. You can erraticate them for a severl months. Spot spray after that. Do this early next time and just spot spray next year.
1/4/2020 09:07:14 am
Does using the method of 2 tbsp of Dawn Dishwashing liquid mixed with spray bottle with water 2/3 full harm the butterfly in any stage if it’s development?
8/20/2020 07:43:49 pm
Hi, I was wondering if it had to be Dawn dish soap, or would any kind work?
8/28/2020 07:46:25 am
Dawn is safely bio-degradable in soil (not if it directly gets into a stream or other water body). It is famous as one of the few big name brands of dish soap that can claim to be bio degradable in soil.
9/17/2021 09:54:54 am
Does this apply to all varieties of Dawn, or just the original? They have so many varieties on the shelf, it's hard to know what is safe.
8/29/2020 10:31:20 am
I've battled aphids for years while raising monarchs & the most effective method that I use after having tried a variety of recommendations is simply blasting them off the plant with water. Remove all caterpillars & use your hose on high pressure to spray them directly. Works like a charm!
8/29/2020 01:24:18 pm
I have relatively small plants that are aphid infested after just a day or so, so I don't think they will survive super-strong spray. I do have Castile, however...
9/17/2021 05:05:09 pm
I've found it much easier, not to blast them off with the hose but to use a combination of squishing with fingertips while applying a slow stream of water from the hose. Works better really, and they don't really stain the fingers.....skin washes great with soap!
11/11/2020 12:48:58 pm
Agree with this method. I use high water pressure to remove the aphids after making sure there are no caterpillars on the plants. It can be tedious to do this but it works. Must be high water pressure as aphids are pretty resistant to anything less.
3/30/2021 12:23:23 pm
The 1st method is to remove them early, delicately using your fingers. The infestations will not be quite is unmanageable if you get on it early. As opposed to waiting for a full blown infestation before you act. Then you almost have to spray the entire plant with a soap based solution. I've also used water to blast them off the plant which seems to work as well but by then the damage is already done in the stunted new green tips that grow. The youngest caterpillars once coming just from the larval stage seem to prefer the softer tips and don't do so well on the harder sunbaked leaves.
3/31/2021 09:08:34 am
Thank you Kenneth. I have been smushing with fingers now and
9/17/2020 10:34:14 pm
Thank you so much! This is just what I need. I planted milkweed specifically for monarch butterflies and as soon as it sprouted, there were aphids all over and it was driving me CRAZY! I really do appreciate this! SAVE THE MONARCHS!
10/23/2020 05:54:26 pm
I have been using 50% iso propyl alcohol with great results,it does not leave a residue.I also rotate Castile soap,saving monarchs is hard work.
11/13/2020 08:32:52 am
Two years ago in hot humid South Georgia the aphid infestation was horrible. My OCD kicked in and I read and read and read. My solution for this year was to plant society garlic which is in the allium family AND French marigolds in and around the butterfly weed. I have 8 areas of milkweed and two had a very minor infestation (no marigolds in this area) during the summer. Starting in late September my issues with aphids were higher but managed by clipping bad plant tips, mashing the bugs, and moving caterpillars to less infected plants. Hope this helps someone else.
Evelyn M Giacchino
1/23/2021 08:14:33 am
Hi- Judy-What does the society garlic and French marigolds do? Is there a smell that these aphids do not like? I keep on spraying with the dawn and water but OMG there seem to be hundreds.
9/23/2022 08:22:40 am
Thanks, I'll try this next year!
2/16/2021 05:25:30 am
I’m battling oleander aphids on my swan plant, which I brought indoors for the winter. I’ve been removing them by hand, which is tedious but effective for a week, or so. Now switching to the dish soap method. Early on I noticed that the soil is also infested with the wee buggers, as well. I took the plant outside on a not-too-frigid day and sprayed the soil with ant spray, which kept them at bay for a couple of weeks. Of the several varieties of milkweed that we have, the monarchs greatly prefer the swan plants. I plant new ones every spring and by late fall they’ve been skeletonized by the monarchs. Perfect!
9/23/2022 08:23:50 am
AGH! wouldn't the ant spray be a poison?????????
2/23/2021 04:58:54 pm
Did no one read the article that recommended against almost everything that y’all are talking about really read the article lease this course
4/19/2021 07:24:01 pm
I have tried everything including what this article suggests to get rid of aphids. The soap is also dangerous to the eggs laid on the underside of the leaves by the monarch butterfly. So you wind up killing the caterpillars before they grow unintended. The only effective method is to inspect the plants every day in spring and physically remove the aphids. I found this year that little bit of effort has really paid off into young healthy plants that are aphid free. You just have to be willing to put in a little time on each plant to inspect and kill manually using your fingers.
8/21/2021 06:14:21 pm
What about when u didn't get aphids until now? It's mid August and i have them on 2 different types of milkweed.
9/17/2021 05:10:51 pm
Kenneth you are absolutely correct! This kind of attention really pays off! Later on in the summer, if some aphids start up again, I just use my fingertips and a slow gentle stream from the hose to dislodge them (having first inspected for eggs on underside of leaves, and tiny new caterpillars). It is mid-September and I still have five big cats ready to pupate; hope they make it OK.
7/27/2022 06:17:56 am
Kenneth I totally agree with your comments. It is the only sure way with no danger to Monarch eggs or larvae. It doesn't take that long to inspect every day or even every other day, to keep the little monsters really down in numbers, and this effort pays off many times over during the summer. I have two large healthy swamp milkweed plants and now the end of July there are no aphids even though I keep inspecting every few days.
6/8/2021 09:46:06 am
what article are you referencing?
3/21/2021 08:44:12 am
I vacuumed them off a couple of times (those orange aphids)
8/23/2021 06:45:47 am
How did you vacuum the aphids?
4/11/2021 06:29:59 am
I took a McDonald's cup filled with soapy water and knocked the aphids off into the cup. After a bit I poured out a big pile of dead aphids. Better than squishing them with my fingers.
4/19/2021 09:31:39 am
For the past couple of years, aphids have annihilated my milkweed seedlings that I carefully grew from seed. On my adult milkweed plants they destroy the plant's attempt to flower and produce seed. The only method I have tried that works is squishing them between my fingers, but one must be diligent, because the aphids can quickly repopulate a plant where you have removed them. This year I am going to try compressed air to (the kind used to clean computer keyboards) dislodge them. Also will try a Giottos Air blaster (search for this on Amazon) to dislodge them. The Giotto device is normally used to blast dust off of camera lenses.
9/17/2021 05:12:31 pm
Matt, how did this method work this summer???? Sounds interesting.
4/24/2021 10:13:42 am
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5/23/2022 10:48:40 am
Seriously with that article here? SMH.
5/4/2021 12:11:40 pm
I used an old tooth brush to brush them off. Seems to work well.
5/25/2021 03:55:10 pm
Ladybugs eat monarch eggs and caterpillars. So will lacewings and wasps.
6/11/2021 09:51:13 am
I'm new to this. I have an extra butterfly net. I'm keeping my milkweed plants in there. I have others outside the net for the butterflys but i need to preserve most of my plants for cattepillers food.
6/11/2021 12:47:02 pm
I tried the dish soap method. After using it, it did kill the aphids however since I’ve used it my milkweed is starting to wilt and get spots. It looks sick. I don’t know if this is because of the soap solution or something else. It could just be wilting because the hot Texas weather I’m experiencing. Any tips?
7/7/2021 06:19:20 pm
I use a mixture of 1 oz alcohol
7/8/2021 10:50:53 am
Newbie at this. If I hand pick all the babies and eggs off and then spray the solution on the whole plant and let it dry, can I put the caterpillars back on to eat?
8/20/2021 01:28:52 am
Same question! Can I put the cats back after treating the milkweed with this solution?
6/15/2021 08:53:08 pm
I'm having a hard time discerning what to do with this aphid infestation!
7/13/2021 10:25:08 am
This is the first time I have a few milkweed infested with the aphids. I’m going to look for white eggs of monarchs and remove them to unaffected plants and try the solution mentioned in the article and then rinse the affected plants. The aphids after hatching have tiny wings so those I’ll drop into soapy water. I have them in both stages. Yuck.
7/30/2021 08:02:09 pm
Saveourmonarchs.org might want to change the picture of the ladybug larvae on this web page. I could be mistaken, but that looks a larva of an Asian Ladybug. The Asian Ladybug is an invasive species in the United States.
8/19/2021 05:56:25 pm
On my asclepias, and swamp milkweed plants there are one-inch orange/rust colored caterpillars with short black fuzz all over them. Should I pick these off? What are they, a moth caterpillar?
10/7/2021 06:51:37 am
I took one to the Master Gardeners office as I could not find this highly invasive caterpillar online. They found it; cycnia collaris, a plain medium sized silver moth. These will strip you milkweed plants, I check three times a day, even now in October, and always find more, no idea how they can hatch and grow that quickly! I pick them off by hand and toss them over the fence; don't think they will survive on Bermuda grass. I still have three Monarch cats on that swamp milkweed bush....hope they make it. I'm in NE Oklahoma.
8/21/2021 08:02:23 am
In addition to the yellow aphids, my first swamp milkweed has dusty white powder on it too. Does neem oil work?
8/30/2021 11:52:02 am
If you just knock the aphids off the plant (via water or otherwise), can they not just climb back on? I don't understand the logic behind this option, but I have seen it called out all over the interwebs for dealing with aphids.
8/30/2021 03:19:18 pm
Aphids and ants have a symbiotic relationship - they need each other. Use ant killer to get rid of ants. Aphids will disappear too without harming the milkweed or any monarch larvae..
Actually, not all aphid species have symbiotic relationships with ants. Unfortunately, A. nerii (the bright yellow milkweed aphid species) is one of those that is not tended an protected by ants, so eradication of ants from your milkweed garden will have no effect on them.
10/6/2021 03:33:25 pm
I use a small, firm pain brush that is small enough to get it between the flower stems and just brush them off. Works great and can work around the caterpillars without bothering them.
10/7/2021 06:55:19 am
I found out someone else uses a small paint brush but brushes the aphids into a bowl of water she holds underneath the affected leaves with her other hand.....that way they are gone for sure and cannot re-infect leaves if they fall on them while brushing. I may just stick to the finger-squash method, but I will try this.
2/17/2022 03:24:48 pm
I asked the nursery where I bought the plants how they control aphids. Terse answer: "We cut them off, burn the cuttings." They have about 5 acres of potted plants.
7/30/2022 08:11:20 am
Actually that is exactly what I did this morning. The eggs were all on one long branch so I cut that branch off. It’s a large plant with so many branches it wouldn’t miss that branch. Looked all over and didn’t see any others. Next time I think I’ll use the small brush idea I saw in comments.
2/19/2022 09:03:59 am
I planted many milkweed plants and was overwhelmed with aphids.I heard rubbing alcohol and water works in a spray bottle and it did fine.Now I use rubbing alcohol and 25% water.It doesn't harm the plants or larve.
4/17/2022 07:22:54 am
If you spray the aphids with soap you will also kill the beneficials and the aphids will rebound much quicker than the beneficials will leaving you in a constant battle. wipe them off and look for Ladybug and lacewing larvae and don't squish them.
5/8/2022 09:24:44 am
I take a tall bowl filled with water and a little dawn, then carefully bend the top of the plants into the bowl and gently wipe them off in the water mixture. This way they drown and you are not harming anything. Make sure there are not any monarch eggs etc. My brother and I both live in Florida and have been raising Monarchs for several years. Together we have raised over 100!
5/8/2022 11:59:29 am
I bought a cheap cordless electric toothbrush via Amazon—at 37,000 vibrations per minute it sounds a little like a dentist’s drill. With a very light touch, the toothbrush mows through Aphis nerii colonies on my milkweed like a hot knife through butter.
6/22/2022 11:56:34 am
Please do not use insecticides even if you moved the caterpillars which isn't really a good idea because there are different milkweed plants and the caterpillar that was on that plant may only be able to eat that kind of milkweed And besides the next generation may come in of monarchs and lay eggs on those same milkweeds and most insecticides leave residue that still will kill them and other beneficial insects So please do not use insecticides they are dangerous to the environment ‼️❣️🤗
7/26/2022 03:26:32 pm
Where do yellow aphids come from? How do they land or get on the Millkweed? What transports them onto the Milkweed plant?
7/27/2022 09:29:03 am
Fatima, the aphids that colonize milkweed are A. nerii—sometimes called “oleander aphids”. They are particular to milkweed and oleander because they have evolved to use the natural toxins in those plants for protection against predators, in much the same way that Monarchs have evolved to use milkweed toxins.
7/30/2022 08:03:12 pm
My milkweed grew incredibly this year and are all over my garden. They are all also infected with aphids. It would be almost impossible to remove the thousands and thousands of aphids by hand. Can I simply kill all the aphids, remove all the milkweed, throw it away and start over with new plants. I didn't know about the problem until it was pointed out to me.
7/30/2022 10:30:29 pm
Monarch caterpillars must have milkweed to survive. While there are many varieties of milkweed, Monarch caterpillars cannot live on plants outside of the milkweed family.
9/22/2022 04:40:18 pm
Still trying to get my first cats. Will get ready for the Spring
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