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MMWD Blog: Think Blue Marin

Welcome to our blog! Written by staff at MMWD, “Think Blue Marin” explores all things water in south and central Marin—water supplies, conservation, new projects, watershed management, and more.

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Oct 30

Vampires in the Garden

Posted on October 30, 2015 at 9:38 AM by Ann Vallee

by Keith Bancroft, Water Conservation Specialist Supervisor

Little orange vampires. That’s what I found—and lots of them, all over the milkweed I planted in my backyard last fall in hopes of attracting monarch butterflies. (Monarch caterpillars feed exclusively on milkweed plants.)

monarch caterpillar
 Monarch caterpillars
My original plan to attract monarchs worked beyond my expectations. One day this past spring I unexpectedly found a dozen monarch caterpillars happily munching away on my milkweed patch. Over the next few weeks I made daily checks on their progress and found them either resting on the underside of a milkweed leaf or, usually, happily munching away.

One day, as I scanned the milkweed looking for caterpillars, I noticed little orange bumps on the stems by the milkweed flowers. Looking closer, I realized these were actually aphids (which I later identified as oleander aphids). At first, there were just a few scattered here and there, but over the next few weeks these turned into an all-out infestation of little orange suckers.

 Oleander aphids on milkweed
Although the milkweed seemed to be holding its own against the orange hoard, I was concerned about the long-term health of the plants and what, if any, impact the presence of large numbers of aphids would have on the monarch caterpillars.

I tried several non-toxic methods of dispatching the aphids. Spraying soapy water on them didn’t make much of an impact. Blasting them off with high-pressure water (by using a small hand-held spray bottle) reduced their numbers for a day or two, but they bounced back. The most effective (and most satisfying) method was to simply crush them between my fingers (which resulted in sticky, orange-stained fingertips).

Then one day, while alternately scanning the milkweed patch for caterpillars to admire and little orange vampires to dispatch, I noticed a newcomer to the garden: a small, round red beetle—a ladybug! The cavalry had arrived! (Or, in keeping with the admittedly forced Halloween vampire theme of this blog, a miniature Abraham Van Helsing had arrived!)

 ladybug larva
 Ladybug larva
Ladybugs and their larvae feed on aphids—up to 50 per day and up to 5,000 in their lifetime—and other soft-bodied insects that feed on plants. I found it amazing that, just as the presence of milkweed had attracted monarchs, the masses of aphids had attracted their natural predator. A few weeks after spotting the first ladybug, I turned over a milkweed leaf looking for aphids to smash (hard to break the habit), and found a new bizarre little critter. I had a suspicion as to what it was, and an internet search confirmed I had found a ladybug larva. Talk about a face only a mother could love. But I was glad to see it, as that meant more hungry mouths to feast on the little orange army. The underside of other leaves held more surprises, as I found a ladybug pupa (the stage between the larva and adult beetle) as well as ladybug egg clusters—future generations of aphid-killers.

 ladybug eggs and pupa
Ladybug pupa with ladybug eggs (circled)
However, finding ladybug larvae, pupae, and egg clusters meant I risked inadvertently crushing them if I continued with my chosen method of aphid eradication. So, I decided to let nature take its course and to depend on the natural balance of prey vs. predator. And, as it turned out, that approach is working just fine. The milkweed doesn’t seem too worse for the wear, even with a sizeable contingent of (one last time, folks) little orange vampires steadily sucking away. The ladybugs and larvae seem to be content eating as many of the little orange pests as they can manage, and monarch butterflies continue to stop by, briefly landing on the milkweed flowers for a quick nectar snack before depositing their eggs on the milkweed leaves. And their caterpillars continue to happily munch away on milkweed before crawling off to a nearby bit of cover to form a chrysalis and transform into the next generation of butterflies (12 so far this year and, hopefully, many more to come!).

monarch butterfly
Adult male monarch
For information on how you can create monarch habitat in your own yard, please visit the Monarch Watch web site and find out more about their “Bring Back the Monarchs” campaign.


Mary Weinberg
November 2, 2015 at 12:28 PM
Please accept my sympathy, Charlene, on the loss of your husband. My heart goes out to you.

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