Japanese Maple Scale Insects
Japanese Maple Scale (Lopholeucaspis japonica) is a stealthy and persistent pest commonly overlooked in your garden. Despite the name, Japanese Maple Scale doesn’t limit itself to just maples. It attacks a broad variety of woody plants including red maples, dogwood, redbud, holly, Japanese holly, boxwood, elm, Itea, and more. Here’s why it’s so problematic and how you can manage it.
What Makes JMS So Tough
Armor-plated and camouflaged: These tiny insects (under 2 mm) have a hard, waxy “test” that makes them hard to kill. Their armor protects them from weather, predators, and many insecticides.
Wide distribution: Originally from Asia, they’re now found across much of the eastern U.S., from Connecticut down to Georgia and out to the Mississippi.
Cryptic lifecycle: All life stages—eggs, crawlers, nymphs, adults—are purple under the shell. But since they’re covered by that white or brown waxy test, you’d never know it without scraping them open. This adds to their “cryptic” reputation; even when you see the scale, you might not realize what species it is.
Overlapping generations: Instead of producing one clean, predictable wave of crawlers, Japanese maple scale produces multiple, highly overlapping generations. This means you can find eggs, crawlers, juveniles, and adults all at the same time on the same plant. For growers, this is a nightmare because there is never a single, perfect treatment window.
Rapid protection: Crawlers start forming their protective waxy cover just three days after hatching—making them less vulnerable to insecticides. This rapid shift from vulnerable crawler to armored nymph shortens the effective treatment window. That’s why monitoring for crawler activity is essential.
Hidden living quarters: Instead of clustering on young twigs or outer foliage like other scales, Japanese maple scale prefers the interior wood. That means you won’t notice them during a quick glance, populations build silently for months, and infestations are often advanced by the time you see symptoms.
Management Tips
Scouting is crucial. Inspect new stock frequently, especially rough bark areas (branch collars are a favorite). Use magnification (like a hand lens) to check for white waxy covers. Gently rub to reveal the brown shell underneath, then flip or squish to check for the purple body or eggs.
Chemical control:
Dormant oil applications in fall after leaf drop or spring before bud break can help suppress populations.
Use insect growth regulators (IGRs) like pyriproxyfen or buprofezin, ideally mixed with horticultural oil, during crawler activity.
Systemic insecticides (neonicotinoids such as dinotefuran, acetamiprid, thiamethoxam) can work—these move into the plant and kill scales feeding on sap.
Imidacloprid isn’t effective against armored scale
Timing matters. Because crawler emergence is prolonged, wait to apply treatments until peak crawler activity. Constant overlap of life stages means not all pests are vulnerable at once, so repeated monitoring and targeted applications are often necessary.
Information and Photos for this article are from Nursery Management Magazine & Maryland Extension