i have a fair amount of common milkweed growing at my place. i'm a fan. it's one of my favorite wild vegetables (at a couple stages!), the flowers are beautiful, and they're the host plant for a few different insects i like to see around, like the red milkweed beetle (one of the longhorn beetles), and of course the monarch butterfly. there were couple years where you would hardly see monarchs flying here, but there have been more over the last few. Last week, give a take a few days, i saw and then forgot about a butterfly laying eggs on some of the milkweed plants that were beginning to fade in the patch next to the barn, where they rarely get direct sunlight and succumb early to one of the fungal diseases (it should be noted that i live in a fairly damp gully in an area of western north carolina that most years is a temperate rainforest. this summer we've gotten predictable afternoon thunderstorms many more days than we haven't). they also get heavy infestations of these fat orange aphids that i don't see on other milkweeds here.
a couple days ago i was walking past that patch and noticed that the plants were very nearly dead and there were a number of monarch caterpillars of various sizes on them. i got a jar and picked off all the caterpillars i could find and moved them to other, much happier milkweed plants in other places, mostly in the big milkweed patch at one end of my home orchard. today i thought that i'd like to document it a bit and went to the dying patch to take a picture. the plants are now standing blackstemmed and dead, but i found a few more caterpillars, wandering apparently confusedly up and down the stems. so i moved them too.
there is now fairly large area where nearly every milkweed plant contains a growing caterpillar. it's nice to go visit the monarch nursery.
New spring shoots, young leaves, flowerbuds, and young seedpods are all edible and tasty, lightly boiled - at which point you can do nearly anything with them. I made a weirdo version of three bean salad earlier this summer with kidney beans, sweet corn, and milkweed flowerbuds that was really good.
Older leaves and seedpods get fibrous and bitter. To me the softer younger material is like a slightly nutty asparagus.
The yellow-orange aphids are Aphis nerii (oleander aphids), a cosmopolitan species.
I grow a lot of milkweeds specifically for monarchs and can tell you they will kill plants, make them unsuitable for larvae, and drastically affect flowering and seed production.
We have lots of ladybird beetles, syrphid larvae, and lacewings but they can't keep up.
You can gently squish them. You can also lightly spray a fine mist of 70% alcohol. You can blast them off with the shower setting on a hose nozzle. If ants find living ones they will carry them back up. But I actually use all of the methods above. Also, if you look at areas under these aphids, they excrete so much honeydew you get thick sticky leaf deposits that usually get colonized by a group of molds commonly referred to as black sooty mold. They are rendered unsuitable for larval feeding and are severely affected by a reduction in photosynthesis.
I save A LOT of seeds each year to further milkweed growing efforts. If I let them progress, pollinators would be affected by lack of flowering and plants dying as would monarch larvae, and seed production.
Even the small Lysiphlebus testaceipes, a parasitoid wasp, can't keep up the their rapid generation rate. However, if you look closely at the aphid colonies, the parasitized ones are the ones that look slightly swollen, dull brown and smooth.
I don't use soap spray on the flowers or plants for the same reasons of protecting monarch larval leaf palatability as well as not putting off the pollinators. The milkweeds are very important food sources for a wide array of pollinators and are always being foraged.
When I use the water blasting, I hold each leaf or inflorescence from behind and hit them with the water shower spray in the front. You need to sort of get used to how much pressure you can blast without negatively affecting plant tissue. You'll also have some fall and regroup on a lower leaf. They can be hit the following day. Ants may bring survivors up as well. The key is to treat it like a game of Whack-A-Mole. It gets easier.
"Si hortum in bibliotheca habes, nihil deerit." [If you have a garden and a library, you have everything you need] Marcus Tullius Cicero in Ad Familiares IX, 4, to Varro.
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