Milkweed is well known for its role in supporting wildlife, but it is also a plant that attracts many leaf-feeding creatures. Its tender leaves and nutrient-rich tissues provide an important food source for a range of organisms, some of which depend on it exclusively. This feeding can be seen in both wild patches and cultivated gardens where milkweed is grown to support pollinators.
The most common type of damage is defoliation, where leaves are chewed from the edges inward or stripped away entirely. Plants that once had broad, lush leaves may appear ragged and thin, with only stems or leaf midribs left behind. In severe cases, entire sections of milkweed can be consumed in just a few days when groups feed together.
Other forms of damage involve the seeds and pods. Certain feeders pierce or chew into developing pods, draining nutrients or destroying the seeds inside. This not only weakens the individual plant but also reduces its ability to reproduce, which in turn affects the populations of animals that rely on milkweed for food or habitat.
Some damage is less obvious but still harmful. Sap-feeding organisms, for example, leave behind curled leaves, yellowing, or stunted growth. They may also produce sticky residues that encourage the growth of sooty mold, further stressing the plant. This subtle weakening can accumulate over time, leaving milkweed vulnerable to other environmental pressures.
Even the roots of milkweed are not immune. Underground feeders may tunnel into the base of the plant, damaging the root system and limiting its ability to absorb water and nutrients. Above ground, the plant may show signs of wilting or reduced vigor without immediately revealing the source of the problem.
Pests And Caterpillars That Eat Milkweed
Monarch Butterfly Caterpillar (Danaus plexippus)
Smooth, striped in white, black, and yellow bands, with black tentacles at both ends, growing up to 2 inches. They exclusively chew milkweed leaves, starting with small bites and progressing to entire leaves, avoiding the toxic latex by eating strategically. As the primary consumer, they can defoliate plants but are vital for monarch reproduction, though heavy feeding may compete with other species.
Milkweed Tussock Moth Caterpillar (Euchaetes egle)
Furry with tufts of black, white, and orange hairs, resembling a tiny brush, up to 1.5 inches long. Young larvae feed gregariously, skeletonizing leaves by eating tissue between veins; older ones consume whole leaves. They can quickly defoliate stands, competing with monarchs for foliage, but natural predators often keep numbers in check.
Striped Garden Caterpillar (Trichordestra legitimata)
Brown and yellow striped body, handsome and slender, about 1-2 inches. Feeds on milkweed leaves alongside other plants like clover or grasses, chewing through foliage. Less specialized than others, it may not heavily impact milkweed but adds to overall herbivory in gardens.
Unexpected Cycnia Caterpillar (Cycnia inopinatus)
Appearance not highly detailed but shows orange-and-black patterning typical of milkweed feeders, small and fuzzy. Exclusively eats milkweed leaves, incorporating toxins for protection. Rare and of conservation concern, it rarely causes significant damage but highlights milkweed’s role in supporting diverse lepidoptera.
Oleander Aphid / Milkweed Aphid (Aphis nerii)
Plump, bright yellow-orange with black legs and cornicles, clustering in large groups. Sucks sap from leaves, stems, and buds using piercing mouthparts, leading to honeydew and sooty mold. Heavy infestations stress plants, deform growth, or kill young ones, attracting predators like ladybugs that may indirectly help monarchs.
Large Milkweed Bug (Oncopeltus fasciatus)
Orange-red with black bands and triangles, up to 0.75 inches, nymphs similar but smaller. Primarily feeds on seeds and sap, but nymphs and adults occasionally suck from young leaves or flowers. Rarely damages plants significantly, though high numbers on seed-producing milkweed can reduce reproduction.
Red Milkweed Beetle (Tetraopes tetrophthalmus)
Bright red-orange with black spots on elytra and long antennae, “four-eyed” due to divided eyes, about 0.5 inches. Adults chew leaves, buds, and flowers after severing veins to drain latex; larvae bore into stems and roots. Can weaken plants in high populations, potentially reducing foliage for caterpillars.
Swamp Milkweed Leaf Beetle (Labidomera clivicollis)
Dome-shaped, yellow-orange elytra with black/blue patterns, black head, about 0.4 inches; larvae gray-orange with black spots. Both stages chew foliage, cutting veins to avoid latex. Prefers swamp milkweed but eats others, potentially stressing or defoliating plants if abundant, though control is simple by removal.
Dogbane Tiger Moth Caterpillar (Cycnia tenera)
Closely related to milkweed feeders, this caterpillar eats both dogbane and milkweed. It has a furry orange appearance and feeds mainly on the leaves. By consuming the plant’s toxic compounds, it gains chemical defenses against predators.
False Milkweed Bug (Lygaeus kalmii)
This insect resembles the larger milkweed bugs but is smaller in size. It feeds on milkweed seeds and sometimes nectar, reducing seed production and affecting the plant’s natural regeneration.
Three-lined Potato Beetle (Lema daturaphila)
Though better known for feeding on nightshades, this beetle also attacks milkweed. Its larvae and adults chew holes in the leaves, sometimes leaving plants ragged and weakened.
Milkweed Longhorn Beetle (Tetraopes femoratus)
A close relative of the red milkweed beetle, this species also feeds on milkweed foliage and flowers. Its larvae live underground, boring into roots, which can reduce the plant’s vigor over time.
Cucumber Beetle (Diabrotica undecimpunctata)
This pest occasionally targets milkweed when populations are high. Both adults and larvae feed on leaves and flowers, leaving behind irregular chewing damage. In large numbers, they may also weaken the plant’s reproductive structures.
Grasshoppers (Acrididae family)
These opportunistic feeders chew large, ragged holes in milkweed leaves. Outbreaks of grasshoppers in late summer can strip entire plants, especially when other vegetation is scarce.
Japanese Beetle (Popillia japonica)
A highly destructive invasive species, the Japanese beetle chews between the veins of milkweed leaves, leaving a skeletonized appearance. Their swarming behavior can cause rapid defoliation in midsummer.
Thrips (Frankliniella spp.)
These tiny insects feed on milkweed by scraping and sucking plant juices. Their presence causes silver streaks, speckling, and distorted flowers, reducing the plant’s health and seed production.