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Milkweed Bug is Killing the Plants

By Lani Thompson
Adult bugs gather in groups on the bottom sides of milkweed leaves.
Brand X Pictures/Brand X Pictures/Getty Images

Milkweed bugs are one of the few insects that can feed on milkweed without being poisoned by the toxins it produces. They serve an important function by controlling the milkweed population. However, when you’re raising milkweed the milkweed bugs are pests.


Milkweed bugs and monarch caterpillars eat different parts of the plant so they don’t usually interfere with each other. Milkweed bugs have piercing mouthparts and suck juices from the plant. Caterpillars eat plant tissue. Anything you do to control milkweed bugs also kills the Monarch butterfly caterpillars feeding alongside them. Try picking the bugs off by hand or spraying them with neem oil when the caterpillars aren’t around. Neem oil doesn’t leave a toxic residue, so caterpillars that return later on won’t be affected by it.


Milkweed bugs are orange-and-black insects with long, tubelike beaks they use to pierce milkweed seedpods. Their bright orange-and-black pattern warns predators that they taste bad. The nymphs resemble adults but don’t have wings and have a different color pattern. Male and female bugs are easy to tell apart. Females have a single black strip and two dots on the bottom side of their abdomens, while males have two black strips.

Life Cycle

Milkweed bugs hatch from orange-colored eggs. The nymphs resemble the adults, but their wings aren’t completely developed and their body proportions are different. There are five nymph stages. The young milkweed bug sheds its exoskeleton before each one, becoming bigger and more developed each time. Milkweed bugs don’t have a pupal resting stage like caterpillars and other insects. The kind of metamorphosis milkweed bugs have is called simple metamorphosis. After the final molt, the bug is an adult.


Milkweed bugs are interesting to watch and to study. Collect adult and nymph bugs from the wild and keep them in a large, clean glass jar. Place a crumpled paper towel in the bottom of the jar for a hiding place. Feed bugs sunflower seeds and provide them with water. Order the eggs from a biological supply company.


About the Author


Lani Thompson began writing in 1987 as a journalist for the "Pequawket Valley News." In 1993 she became managing editor of the "Independent Observer" in East Stoneham, Maine. Thompson also developed and produced the "Clan Thompson Celiac Pocketguides" for people with celiac disease. She attended the University of New Hampshire.