Want to Meet the Beetles? Better Hurry, Removal of Milkweed Beetles from San Antonio River’s Milkweed Patch Imminent

An invasion of red-and-black milkweed beetles have made a temporary eyesore of the San Antonio River’s celebrated Milkweed Patch on the Museum Reach.  The striking insects, whose colorful torsos suggest the patterns of a tiki mask, have moved into the 1200-square foot Tropical milkweed garden on the banks of the San Antonio River just south of the Pearl Brewery  in a classic play of nature’s cycles.

Milkweed Beetles have taken over the Milkweed Patch

Milkweed Beetles have taken over the Milkweed Patch

The beetles, which look like ladybugs on steroids, don’t bite, sting or carry diseases. They do, however, defoliate milkweed plants, and have left the highly trafficked stretch of the River with some unattractive bald spots.

Migrating Monarch butterflies moved through town earlier this spring, laying the first generation of eggs in their annual migration at the Milkweed Patch.  The resulting acrobatic caterpillars occupied the Patch, feasting on milkweed leaves, the Monarch butterfly host plant.  Late straggling Monarchs continue to mingle with our local colony but the pervasive milkweed beetle, Labidomera clivicollis, dominates.

Milkweed Patch going bald thanks to milkweed beetles

Milkweed Patch going bald thanks to milkweed beetles

Volunteers for the Monarch Larvae Monitoring Project (MLMP), a citizen scientist program based at the University of Minnesota and which aims to better understand the Monarch life cycle and migration, have noticed fewer Monarch caterpillars and chrysalises during their weekly observations as beetles consume the milkweed leaves.

Discussions ensued about possibly pruning the milkweeds, which typically die back in winters when a hard freeze occurs.   That didn’t happen this year.  But San Antonio River Authority staff determined a better approach would be to hand-remove the beetles, THEN prune the plants.

Milkweed beetles have defoliated the Milkweed Patch. But aren't they cute?

Milkweed beetles have defoliated the Milkweed Patch. But aren't they cute?

“We believe this to be a holistic management approach with minimal negative impact to the environment that is consistent with our commitment to the local community for the project, ” said Steven Schauer, Manager of External Communications at the San Antonio River Authority (SARA), which oversees maintenance of the area.   The Museum Reach stretch of the San Antonio River was designed as a manicured, urban park setting, unlike the Mission Reach section, which is managed as a native riparian restoration.

SARA deserves praise for working with MLMP  volunteers and resisting the use of pesticides to address the problem.   A round of pesticides would quickly rid the area of

Gulf Fritillary

Gulf Fritillary, photo courtesy NABA.org

beetles (and other plant pests) and would also jeopardize the Monarchs’ and other butterflies’ continued colonization of the River.  Just north of the Milkweed Patch is a huge Passionflower planting, where Gulf Fritillary butterflies have made their home and are breeding.

If you’d like to “meet the beetles,”  better do so in the next few days.  The critters will be less visible once the hand removal is accomplished.

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8 thoughts on “Want to Meet the Beetles? Better Hurry, Removal of Milkweed Beetles from San Antonio River’s Milkweed Patch Imminent

  1. Is hand removal a euphemism for squashing or are they re-located? I’ve had some flat looking beetles on mine and their eggs are yellow. I’ve been removing them too, especially since I’m down to my last batch of milkweed! Every single caterpillar I put on that bad batch of milkweed died and I haven’t lost any on the homegrown or the scraggly plants I bought. I destroyed the bad plants because I didn’t want the butterflies even getting the nectar. So much for healthy looking plants! Now I’ll plant the good stuff and I’ll have plenty next year but lesson learned: Even if they tell you (emphatically) that there were no pesticides used, they may not know.

    I have another batch of chyrsalises going. This has been so much fun and I’ve learned a lot!! I love watching the whole process. I’m much more aware of what is going on in my garden (a lot!) so, thanks Monika!!! I know these may be local monarchs but it’s still been a blast!!!

  2. Hand removal means getting them off the plant. I assume that since they only eat milkweed leaves, without their food plant they will die. Not sure about the squashing.
    So glad you’ve learned and enjoyed the process. It really does make the garden more interesting and forces you to see things differently.

    MM

    PS You can now expand to Gulf Fritillaries, Swallowtails and more!

  3. That is so sad about the milkwee patch. Are they going to replant it? My three plants are doing fine, so far.
    Maybe because they are hidden among some salvias and mint. I have not seen any swallowtails at all, even though I have good sources for them to lay their eggs on.

    • I believe they will replant. The overdose of milkweed beetles is likely the result of the large monoculture.
      MM

      • Milkweed leaf beetle outbreaks are unusual in my experience. Even finding even single individuals here in Texas is relatively unusual. The outbreak may have been caused by the same factors causing outbreaks of various butterflies, moths and katydids across Texas.
        Outbreaks can occur on native milkweed as well. See this outbreak on Asclepias incarnata

        • Common name is Swamp Milkweed Bug and they occur on A. incarnata. Do they occur on other native milkweeds?

    • Should read “to” rather than “top.” I agree with Monika that A.c. should not be the only plant is the 1200 sq.ft. garden. It would be nice to make it a pollinator garden with host and nectar plants.

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