Those are aphids in different stages. You can't use pesticides of course because it would kill your Monarch caterpillars as well. I use those cheap disposable latex gloves and squish them. If you get most of them, your milkweed will be fine. A heavy infestation is hard on it and might kill it. Watch out for eggs and caterpillars on the underneath side of the leaves.

Lots going on there! The yellow oleander aphids at various stages of development plus the larger, swollen bodies of oleander aphids, indicating that the aphids have successfully been killed by parasitoid wasps. The big carcasses are called ”aphid mummies” and are a cause for celebration! The tiny wasp lays her egg under the skin of the aphid, leaving it to develop fully inside the hapless aphid. The tiny wasp larva feeds on the aphid from the inside until the victim dies, swollen and ”mummified”. It ((wasp) then chews its way out, fully adult by then and ready to find its own aphid to parasitize.

I see several aphid mummies in your picture; they are brown or blackish. You might also see little white flakes strewn around like discarded laundry. Those are the cast off exoskeletons contributed by the growing aphids. Aphids typically lay eggs only in the fall, in order that they may overwinter under bark, in nooks and crannies. Most people have never seen an aphid egg. What you are seeing is a community of sisters, each of whom will bear a few dozen live clones within a matter of days of being born themselves. All without the usual input from any male aphids whatsoever. Until the fall when the days become shorter, that is.

You should know what aphids look like. They come in a wide assortment of colors, depending upon the species……yellow aphids are oleander aphids, found on oleanders, milkweeds, and other plants in the oleander family.

So what are the orange round things? Those are the oleander aphids? Not sure why I should be celebrating in that large infestations of aphids can weaken the plant, and this plant has a large infestation. Should I be seeing larger swollen bodies? I see large orange balls and small black balls.

All of the round things are oleander aphids. Big, small, black, brown, and yellow. Those that have been parasitized become immobile, swollen, and change color as the tiny wasp embryo develops inside of them. The black bodies are aphids that have been fully devoured on the inside by the wasps, which will soon emerge.

We like to see those aphid mummies because it’s an indication that perfect organic control is at work in front of your very eyes. The parasitoids will never completely halt the army of aphids, but they can truly help manage the population. When the wasps finish their development cycle inside the host insect, they chew a hole and emerge as a fullly mature, winged adult, ready to fly away to lay eggs on more aphids. Understand?

Click here for images

OK, but the fact that I see a large pile of oleander aphids that have NOT been parasitized means that there is still an infestation that can damage my milkweed, though it's nice to see that some measure of organic control is taking place.

Take your garden hose and spray your plants! Use one hand to hold the hose and the other to quickly squish the aphids on the stem and under the leaves. Teach those aphids a lesson (🤬) but don’t harm the plants by a too strong spray.

Aphids reproduce at a crazy rate, probably unmatched by any other insect. You will need to keep up with them by spraying/squishing regularly. It is, by far, the most efficient method of control and takes only seconds per plant.

It’s worth mentioning that the traditional method of organic control, ladybugs, are not very helpful in controlling oleander aphids. The ultra-sticky sap is not tolerated well by the ladybugs…and those plump aphids are full to the brim of the gloppy stuff.

I'll probably just use horticultural soap solution.

Oh, I thought you were growing the milkweeds for the Monarchs and other nectar feeders. Bees love to forage on milkweed, too. My mistake for making that assumption. Squeamish about the squishing?

Perhaps you can look up to see what the butterfly eggs and hatchling caterpillars look like and avoid spraying if you see any. Also avoid spraying the actual flower heads, especially during the daylight hours, in order to prevent harm to those important pollinators