MASTER GARDENERS: Monarch butterflies need our help

In a February CBS news report, Li Cohen relayed that 26% of monarchs were lost between 2019 and 2020 due to several reasons.

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In a February CBS news report, Li Cohen relayed that 26% of monarchs were lost between 2019 and 2020 due to several reasons. There are things that we can do to help these icons of beauty and freedom that we love so much. One thing is to learn more about what we can do. I realized how little I knew when a Christmas gift book, “The Monarch” by Kylee Baumle, came my way. It was an eye-opener.

I had thought that ingestion of milkweed by the caterpillars produced a toxin that largely protected Monarch caterpillars from predators, but learned some predators are not affected. It is not only climate changes, toxic chemicals, habitat destruction and reduction of milkweed throughout their 1,200 to 2,800-mile migration and where they reproduce that have put them on the road to extinction.

Even creatures we consider beneficial are culprits. The tachinid fly is one. It lays eggs on the caterpillar; they hatch and their larvae burrow in, munch away and then pupate right in the caterpillar. It can sometimes survive and make it through the chrysalis stage before dying. The caterpillar may look drained or the chrysalis might have a white, gelatinous strand hanging from it.

The tachinid doesn’t dine exclusively on monarch caterpillars; it does the same thing to caterpillars we consider pests but monarchs usually lay only one egg per plant. With plant numbers are already reduced, fewer caterpillars pupate and become butterflies.

Spined soldier bugs and other stinkbugs are other villains. They also puncture the caterpillar but then suck the life right out of it. I have seen those dried-up caterpillars on my plants but didn’t know the cause.


Spiders conceal themselves so well by color or stealth, then hide on flowers and bite the butterflies as they feed on nectar. Butterflies can also be caught in their webs, the tables spiders set to ensnare them. The monarch dies and gets rolled up in the web for a spider’s late-night snack.

A pollinator that is usually no problem to us during the summer goes into a feeding frenzy as fall and frost approaches. Paper wasps sting us but they also go after the medium-sized caterpillars. They are the ones that should develop into the monarchs that fly south in the fall migration!

Tiny Trichogramma wasps are also beneficial biological control insects. However, they lay eggs in the monarch egg; larvae hatch and kill the little developing caterpillars.

Chalcid wasps, another tiny insect, hits the monarch in the chrysalis stage. They poke their piercers into its shell-like casing and lay eggs; larvae hatch and kill the developing pupa, only emerging as adult wasps.

No fire ant enemies exist in northern Minnesota, at least, but I have wondered many times as I have watched those little white eggs that one finds on the bottom of milkweed leaves or the caterpillars that I have observed munching on the leaves totally disappear or look very sick. Now I know!

Education is a powerful thing but only if we allow it to empower us to do something about the challenges we face. Opportunities abound to help monarchs survive. Plant milkweed, push for protection, avoid insecticides. By planting more milkweed for egg-laying and caterpillar feeding and flowering plants to provide nectar, the more opportunities monarchs have to increase in numbers. Maybe each of us can make a difference.

These local garden articles will reach you each week throughout the gardening season, but gardening information can be found year-round by clicking on "Yard and Garden” at the University of Minnesota Extension website, , or by visiting our Facebook page at .

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