The Spotted Lanternfly (Lycorma delicatula) is an invasive planthopper detected in the United States in 2014. This insect damages crops and trees by feeding on plant sap, threatening industries like grape production and timber. Milkweed (Asclepias species) is a native plant famous for being the sole host for Monarch butterfly caterpillars and possessing natural defenses. The public frequently asks whether milkweed’s toxic properties can control the Spotted Lanternfly. Answering this requires examining the insect’s biology and the plant’s chemical makeup to establish reliable management practices.
The Relationship Between Milkweed and Spotted Lanternflies
Milkweed is not supported as a reliable control method for the Spotted Lanternfly (SLF). While anecdotal reports exist, scientific consensus does not confirm milkweed as a practical tool for pest management. The SLF did not co-evolve with North American milkweed species in its native Asian habitat, unlike the specialized Monarch butterfly. Spotted Lanternflies are not primary host plants and typically do not feed on them enough to ingest lethal toxic compounds. Although some early laboratory studies suggest feeding on common milkweed may result in high mortality for SLF nymphs and adults, this finding is not yet a field-tested, recommended strategy.
Understanding Milkweed’s Chemical Defenses
Milkweed plants defend themselves against most herbivores by producing potent compounds called cardiac glycosides, or cardenolides. The milky white sap, or latex, is the delivery system for these defensive toxins. Insects like the Monarch butterfly caterpillar have evolved specialized mechanisms to tolerate and sequester these toxins, gaining a chemical defense against predators. The Spotted Lanternfly evolved elsewhere and feeds on a wide range of plants, possessing no specialized tolerance for these compounds. Since milkweed is not a preferred host, the SLF typically does not remain on the plant long enough to ingest a lethal dose of toxins before moving to a more suitable host.
The Actual Diet of the Spotted Lanternfly
The Spotted Lanternfly is a polyphagous pest, meaning it feeds on a wide variety of plants, with a host range that can exceed 100 species globally. The insect uses its proboscis, a straw-like mouthpart, to penetrate the bark and stems of plants to feed on the nutrient-rich phloem sap. The most preferred host for the SLF is the invasive Tree of Heaven (Ailanthus altissima), particularly in its later nymph and adult stages. Other economically significant host plants include grapevines, fruit trees like apple and peach, and various hardwoods such as maple, black walnut, and willow. As the lanternflies feed, they excrete large amounts of a sugary liquid called “honeydew.” This sticky substance coats surfaces and encourages the growth of sooty mold, which blocks photosynthesis and further damages the plant.
Effective Strategies for Lanternfly Management
Since milkweed is not a proven method, homeowners should focus on actionable strategies for managing Spotted Lanternfly populations. A highly effective, non-chemical approach is the destruction of egg masses, which are typically laid on smooth surfaces like tree trunks, rocks, or outdoor furniture. These masses should be scraped off between November and early April and crushed or placed into alcohol to ensure destruction. Another mechanical control method involves using sticky bands wrapped around the trunks of preferred host trees to trap nymphs. It is important to wrap the sticky material with a protective barrier, such as a wire mesh or cage, to prevent accidental trapping of non-target animals like birds or squirrels.
Chemical Control Options
Targeted chemical controls should be used judiciously, focusing on the nymph and adult stages when populations are high. For direct contact, insecticidal soaps and neem oil can be applied directly to clusters of lanternflies, though they require repeat application due to limited residual effect. For more severe infestations on high-value trees, systemic insecticides like dinotefuran or imidacloprid can be applied as a soil drench or basal bark spray. These systemic treatments should be timed carefully, typically after the tree has finished flowering, to protect pollinators.