Magnolia scale (Neolecanium cornuparvum) is a common soft scale insect that primarily infests magnolia trees. This insect is one of the largest soft scale species found in North America and can cause significant damage to its host tree, often becoming most visible in late summer and early fall. Homeowners often worry whether the insect poses any danger to people or pets sharing the yard. This article addresses the question of human safety and the potential risks associated with a magnolia scale infestation.
Zero Direct Threat to Human Health
The magnolia scale insect presents no direct threat of harm to humans, household pets, or livestock. This soft scale is largely immobile throughout its adult life stage, except for the tiny, newly hatched nymphs known as crawlers. The insect does not possess a stinger or the ability to bite or physically attack people or animals. It feeds by extracting sugary sap from the host tree’s phloem tissue using specialized mouthparts. Magnolia scale is an outdoor pest that exclusively feeds on woody plants and does not infest homes or food sources.
Are Sooty Mold and Honeydew a Risk?
The most common sign of a heavy infestation is honeydew, a sticky, sugary liquid the insect excretes as waste. This sugar-rich material promotes the growth of sooty mold, a black, fungus-like coating that covers leaves, branches, and surfaces beneath the tree, such as patios or vehicles. While unsightly, sooty mold is generally considered non-pathogenic to humans. It is an external growth that feeds only on the honeydew. For most individuals, contact causes no reaction beyond stickiness and staining. However, people with severe mold sensitivities may experience temporary, minor irritation upon heavy exposure to the fungal spores, though this is rare.
What Does Magnolia Scale Look Like?
Magnolia scale is highly noticeable due to its size; the mature female is the largest soft scale insect in many regions, reaching up to half an inch in diameter. Adult females are typically found plastered to the stems and twigs, appearing as large, convex bumps. Their color varies, presenting as pinkish-orange, peach, or brownish-purple, often covered with a white, waxy or fuzzy coating. Visual confirmation often occurs in late summer when the females mature and produce copious amounts of honeydew. This sticky substance coats the tree, making the scale infestation extremely obvious.
The Primary Damage to Magnolia Trees
Although the scale poses no threat to human health, it is detrimental to the health of its host tree. The insects use piercing-sucking mouthparts to remove large quantities of sap from the tree’s phloem. This constant draining of resources leads to a reduction in vigor and stunts the plant’s overall growth. Heavy infestations often result in the yellowing of leaves, premature defoliation, and the dieback of twigs and branches. Furthermore, the thick layer of black sooty mold that grows on the honeydew covers the leaves, which reduces the surface area available for photosynthesis. Over time, an untreated population can severely weaken or potentially cause the death of the magnolia tree.