Jennifer is an environmentalist from Ohio. She is passionate about advocating for the planet and wildlife through gardening and education.
Why are Aphids a Problem?
The most common aphid species you are likely to find infesting your milkweed plants is the tiny orange Aphis nerii, also known by the common names oleander aphid or milkweed aphid. These aphids suck the sap out of milkweed plants and can reduce flower and seed pod fertility of the plants. As an invasive species, beneficial native insects are less effective at controlling them than they are in controlling native aphid species. In extreme cases of infestation, aphids may completely kill your milkweed plants, destroying the monarch butterfly habitat you worked so hard to create.
Signs of Aphid Infestation on Milkweeds
The most obvious sign of an aphid infestation is obviously seeing the small orange insects crawling all over your milkweed plants. In addition to seeing the bugs themselves, you may notice misshapen or yellowed leaves or sticky residue on the plant’s stem. The plant may have a deformed appearance or be failing to grow.
If you notice only a few aphids on your milkweed plants, you can simply manually remove them by carefully picking them off the plant by hand. If you choose this method, be sure to wear gloves while handling these pests. You can also use a small brush to manually dislodge and remove aphids if you don’t want to handle them directly.
You can also use a steady stream of water to displace these pests in the early stages of infestation. Simply hold onto the plant with one hand to prevent stem breakage and use your garden hose or a spray bottle to spray the aphids off the plant with water.
If plain water or other manual removal methods aren’t enough for your infestation, consider rinsing the plant in a solution of soapy water to kill off the aphid invaders. Add 2 tablespoons of fragrance-free eco-friendly dish soap to one gallon of water. Use a spray bottle to spray the aphids, then rinse the plants with clean water. You may have to repeat several times to get rid of all the aphids.
Another common household item that can be used for killing aphids is rubbing alcohol (isopropyl alcohol). If other methods aren’t working or if you have a very heavy infestation, isopropyl alcohol may do the trick.
Isopropyl alcohol can harm monarch butterflies, their caterpillars, and their eggs, so use extreme caution when trying this method. Consider applying near dusk when pollinators are less likely to come in contact with the plants.
Some gardeners use beneficial insects that naturally prey on aphids as pest control. Release natural aphid predators such as lady bugs to get rid of your aphid infestation.
For a more long-term solution, plant plants that attract ladybugs and other aphid predators to encourage these beneficial bugs to stick around. Plants that ladybugs can’t resist include:
Be careful if you choose to use ladybugs, as these insects have been known to also prey on monarch eggs and caterpillars.
Neem oil is a natural oil that comes from the Indian neem tree and can be useful in repelling and destroying harmful insects, including aphids. You can find it at many garden centers and big-box home improvement stores in a spray bottle. Simply spray the neem oil on the infected plant. It is best to do this near dusk so that the leaves won’t be burned in the hot mid-day sun, and to prevent beneficial pollinator insects from coming into contact with the oil. Though some sources claim neem oil is safe for beneficial insects, it is best to avoid the risk of harming our pollinators.
It may take several applications of neem oil to stop the aphid infestation.
Diatomaceous Earth (or DE) is another natural way to kill aphids on your milkweed plants. DE is a powder made from fossilized algae sediments and is non-toxic to plants and mammals. It is often used to kill harmful insects and is thought to work by drying their bodies out. It can be purchased at hardware stores, garden centers, etc.
To use DE to treat an aphid infestation, simply dust the infected plant with a thin, it visible layer of the powder. Wait a few days to check its effectiveness before adding additional layers.
Prevent Aphids from Coming Back
There are several things you can do to prevent aphids from returning once you get rid of the infestation (or prevent them from invading your garden to begin with).
Stressed plants are more susceptible to aphid infestation. Be sure the plant each type of milkweed in the correct environment. For example, swamp milkweed needs moist soil, while butterfly weed needs better drainage.
Also, avoid over fertilizing your milkweed plants. As native plants, they don’t need as much fussing as more exotic ornamentals to thrive. Aphids tend to be more attracted to plants with higher nitrogen content, so giving your plants too much fertilizer can increase their appeal to aphids.
One other easy way to help keep pests at bay is to sprinkle used coffee grounds around the base of your plants. The smell of coffee may deter aphids from infesting the plant. The downside is that the coffee grounds need reapplied often as they are washed away to maintain effectiveness.
Another solution is to plant plants that aphids dislike around your milkweeds. Some such plants that may be helpful in repelling aphids are:
In addition to planting things that repel aphids around your milkweed plants, you may also want to avoid planting things that attract aphids. Some plants that aphids are especially attracted to include:
- green beans
- Brussel sprouts
Avoid planting these plants near your milkweed plants if you are worried about aphids infesting your milkweed.
What Not to Do
You’ll notice that I did not mention any chemical pesticides. You should not use any harsh chemicals on your garden plants for pest control or otherwise. These chemicals harm beneficial wildlife and the ecosystem. They may also pose health risks to humans and pets. There are many other safer, more natural solutions.
Aphid Prevention and Removal
To most effectively protect your milkweed plants from aphid infestation, try to employ a number of tactics to prevent the pests from invading your garden in the first place. If you find that one or more of your milkweeds has become host to these unfriendly invaders, you may need to try a combination of the different methods I have outlined to kill them once and for all.
- Orange Aphids on Milkweed | University of Maryland Extension
Oleander aphids, (Aphis nerii) are little orange insects that commonly infest milkweed plants.
- 10+ Clever Ways to Kill Aphids on Milkweed
Discover how to get rid of aphids on milkweed using a simple spray, pungent plants, or beneficial bugs, so that monarch larvae can flourish in your garden.
- How to Get Rid of Aphids on Milkweed - Save Our Monarchs
- How To Control Aphids On Milkweed Plants- Monarch Butterfly
Aphid control is essential if you're growing milkweed plants for monarch butterflies. Here are10 ways to control aphids and save more milkweed for monarchs.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2021 Jennifer Wilber
Miebakagh Fiberesima from Port Harcourt, Rivers State, NIGERIA. on August 16, 2021:
Very useful information. Thanks.