A swallowtail butterfly alights on ironweed flowers in Eastern Iowa. The native plants appear unaffected by pests such as aphids, which are particularly fond of milkweed, an essential food for another butterfly, the monarch. (photo/Cindy Hadish)

For the past decade, my insect nemesis has been the voracious Japanese beetle, but this summer, we’ve been battling an aphid invasion.

These tiny sap-suckers are particularly fond of milkweed, the sole food source for monarch caterpillars. They appear uninterested in ironweed, (Vernonia fasciculata) and other native plants that are beneficial for pollinators.

Aphids are shown on milkweed plants in Eastern Iowa. (photo/Cindy Hadish)

More: Differences between monarch and swallowtail caterpillars

So the spread of milkweed throughout our backyard — intentionally allowed to grow to benefit monarchs — was tempered by the devastation wreaked by the attacking aphids this summer.

The sticky residue attracts ants and flies.

Some gardeners say aphids won’t kill the milkweed and that monarch mamas won’t lay their eggs on infested milkweed plants.

But I’ve seen monarch caterpillars struggle against the aphid invaders and have moved several of the tiny “cats” to locations on unaffected milkweed.

If you’re growing milkweed for monarchs, and really, what else is the point of allowing it to grow, avoid chemical means to control the aphids.

A monarch alights on milkweed, an essential plant for the butterfly’s life cycle. (photo/Cindy Hadish)

I’ve tried spraying streams of water, to mixed results, and squishing the invaders, but at times, have had to resort to removing parts of the plants where they are located and discarding it.

Carefully examine the milkweed to make sure there are no monarch caterpillars or monarch eggs but if so, relocate to other milkweed.

Some advocates raise the butterflies indoors.

More: Raising a black swallowtail butterfly

Natural predators of aphids include ladybugs, but I’ve seen none of those this year.

Other natural aphid control methods are offered on the Gardening Know How website.

Learn more about monarch efforts in Iowa.

A relocated monarch caterpillar crawls along milkweed leaves. (photo/Cindy Hadish)