What In The Milkweed?!

I’ve discovered some weird and wondrous things searching for monarchs in our milkweed patch, but I’ve never come across anything resembling this U.M.O in our Minnesota garden.

Mystery in the Milkweed Patch. Have you seen these before?
Clay Pots for Smurfs?

These twin globes are securely attached to the bottom of this common milkweed leaf and look/feel like an accidental splattering of dried mud. However, their identical shapes and suction cup appendages suggest otherwise.

What lurks beneath the common milkweed? You tell me...
Here’s lookin’ at you

I honestly have no idea what these little brown globes could be, so I’ve assembled a short list. It needs a little work:

  • mini-wasp nests
  • clay pots for smurfs
  • googly eyes
  • insect eggs
  • insect chrysalides
Update: Thanks to everyone in the community who shared their experience to help me identify the foreign object on my milkweed.¬†The mystery has been solved…

Many of you guessed that it was some sort of mud dauber or potter wasp. This is bad news for monarchs since the larva inside these domes feed on monarch caterpillars conveniently brought back to them by parents scouring milkweed leaves for monarch caterpillars.

Potter wasps are beneficial pollinators, but they're also monarch predators, taking monarch caterpillars from milkweed leaves and feeding them to their little wasp larvae. One of the many predators that keeps the monarch survival rate outdoors to under 5%.
On The Hunt | Photo by Barbara Eckstein

To verify their identity, I opened up the globes:

potter wasp larvae feed on monarch caterpillars
Out of Pot

While potter wasps are monarch predators, they are also beneficial pollinators in your butterfly garden. I welcome them as garden guests, but they’ll need to find a home outside of our milkweed patch!

What strange foreign eggs or objects have you found on your milkweed plants? Leave a comment below:

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    • says

      Hi Mary, I wasn’t able to move them, but maybe I didn’t try hard enough. I’ve gotten a few good leads now so I will investigate tomorrow and report back. Thanks for your post!

      • says

        Potter wasp, yes. Predator of moth caterpillars, yes. Predator of monarchs, not likely. It is actually benefcial because it catches caterpillars of many moths, some of them may be pests.
        It is not a dauber wasp. Those make different types of clay nests, not cute liitle pots.
        The image is not that of a potter wasp but a vespid in a different subfamily, probably Polistes. You may want to replace that image.

        • says

          Thanks so much Beatrice, that one slipped past me! I fixed the photo…

          I don’t think potter wasps are common monarch predators like paper wasps, but I talked to someone else who found potter wasp nests on their milkweed too.

          It’s hard to believe they would build nests on milkweed if they weren’t feeding tussocks and monarchs to their caterpillar-fed larvae.

          Many species have evolved to withstand the toxins in milkweed…

  1. Helen says

    Hi Tony

    I started taking my milkweed out for some sun and air
    But noticed that the leaves are bleaching out or fading from a nice glossy green to a dull almost bleached light green did I kill them?
    They aren’t growing like before. I wish that I could send you a picture.

  2. says

    Hi Helen,

    they need some time to adjust to being back outside. I actually cut back all the stems of our tropical milkweed and let them start putting out new foliage. I use the stem cuttings to start new plants.

    Your other option is to put them outside in shadier conditions and gradually move them into sun over the next few weeks.

    If these are mature plants, just pinch off the affected leaves and let new growth emerge. Good luck, Tony

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