Oleander Aphids, (Aphis nerii Boyer de Fonscolombe), sometimes called the milkweed aphid, are tiny, bright yellow or orange insects with black legs, cornicles, antennae, and abdomen.
Adults can be wingless (apterous) or winged (alate).
Its common names include:
- oleander aphid
- milkweed aphid
- sweet pepper aphid
They most frequently attack Oleander, but they’re found on the common milkweed or butterfly weed plant, Nerium oleander, and citrus trees.
Usually reappearing in late summer and autumn when plants are producing new growth.
They take over anything in the Asclepias and Apocynaceae families.
Gardeners who often grow milkweed plants to attract the monarch butterfly are all too familiar with this pest.
Most Oleander Aphids are wingless, but when colonies become overpopulated, some of the insects will grow wings so they can fly to a new location.
Oleander Aphids are most likely to be found in very warm climates such as:
They are especially abundant in these warm locations because they originally came from the Mediterranean areas along with their favorite host plant, the Oleander.
The Oleander plant is full of highly toxic sap which these aphids love and ingest from the phloem of its host plant.
When you are handling Oleander plants in your attempts to get rid of the aphids, be very careful.
Every part of the Oleander is extremely poisonous (i.e., flowers, seeds, and clippings).
Be sure to wear gloves, long sleeves, and eye protection when handling Oleander.
Once you’re done, toss your clothing straight into the wash and take a shower (not a bath).
What Do Oleander Aphids Do?
Like other aphids, Oleander Aphids use their piercing mouthparts to suck the sap from the host plant.
They also produce sweet, sticky excrement known as honeydew, which attracts ants.
As with all sorts of aphids, ants are a harbinger which lets you know the Oleander Aphids are present.
Ants collect the honeydew and carry it back to their burrows to be used as a food source.
They’ve also been known to farm aphids by moving them about from place to place and even milking (squeezing) them to increase the production of honeydew.
In addition to the damage done by the aphids, the honeydew itself is detrimental to your plants.
If it accumulates, it provides the perfect environment for the development of black sooty mold.
This thin layer of mold can cover the surfaces of the leaves of your plant and block the sun, thus hampering photosynthesis.
The aphids attract large colonies of natural enemies like hoverfly larvae, lady beetle larvae, and lacewing larvae during spring/summer.
The life cycle of these pests is quite unique as they’re parthenogenetic, meaning the adult females clone themselves and do not require mates to reproduce.
What Can You Do About Oleander Aphids?
Just as with other aphids, control of Oleander Aphids is fairly simple and easy.
Good care habits will prevent them from taking hold in the first place.
For example, if you overwater, you will be more likely to attract aphids.
They like moist places.
You should also keep your plants properly thinned and planted at the correct distance from one another to provide good air circulation.
Breezy, dry surfaces are less conducive to aphid infestation than dense, closely packed, slightly damp foliage.
It’s also a good idea to encourage natural garden predators such as:
- Ladybugs (more on What do ladybugs eat?)
- Syrphid fly
- Parasitic wasps (Lysiphlebus testaceipes)
… which make short work of aphids of all sorts.
What If It’s Too Late For Prevention?
If aphids are present on your Oleander or other plants, you may be able to get rid of them by simply blasting them with the garden hose.
When you wash them off the surface of the plants, they are unlikely to be able to find their way back.
Spraying with a Neem oil pesticide solution can kill them off and also prevent their return for a brief period.
Use commercial insecticidal soaps which are available at your local garden center, or mix up your concoction of tap water and plain dish soap.
Just a tablespoon or so of dish soap mixed into a quart of water and put into a spray bottle makes an effective weapon against Oleander Aphids.
You should spray a heavy stream of water on every surface of the plant completely and let the soapy water stand for about an hour.
Follow up with a good strong, thorough spraying with your garden hose.
Check daily to see if the aphids have returned, and if they have, repeat your efforts.
Even though insecticidal soaps and Neem oil solutions are less damaging to natural predators than insecticides and pesticides, go with the simple water solution first to avoid doing any damage to beneficial insects.