Trees face plenty of seasonal stress—from storms and drought to human activity. But two of the most persistent and damaging threats come from invasive pests: bagworms and spotted lanternflies. These insects can weaken or defoliate healthy trees if not identified and treated early. Knowing what to look for and when to act can save you time, money, and the loss of cherished landscape trees.
Bagworms
Bagworms are small, caterpillar-like pests that build spindle-shaped silk cases—“bags”—covered in bits of bark and foliage. These bags hang from branches like holiday ornaments and often go unnoticed until damage is done. They’re voracious defoliators, feeding on leaves and needles from early summer into late August. Evergreens are especially at risk; bagworms on arborvitae and other evergreens like spruce, juniper, pine, and cedar can decline rapidly after even partial defoliation. Effective arborvitae pest control requires vigilance due to the tree’s dense structure, which makes it a frequent target.
Bagworm damage reduces curb appeal as visible browning and dead patches make trees look unhealthy and unkempt. Common bagworm infestation signs include hanging, teardrop-shaped bags (1–2 inches long) on branches, thinning or browning needles and leaves—especially in evergreens—and progressive defoliation that begins in June and worsens into August.
To protect your trees with targeted bagworm tree treatment, hand-pick visible bags in winter or early spring before larvae hatch. Many homeowners ask how to remove bagworm cases without harming the tree—manual removal followed by professional spraying is most effective. Prune affected branches if the infestation is localized. Apply insecticidal sprays in late June to early July when larvae are actively feeding—this is best done by professionals to ensure thorough coverage.
Spotted Lanternflies
Originally from Asia, spotted lanternflies are an invasive species spreading rapidly in eastern states. These invasive planthoppers pose a growing threat to many tree species and are now part of broader concerns around spotted lanternfly control and tree pest prevention. They feed on sap, piercing bark and pulling nutrients from the tree, which can lead to lanternfly tree damage such as leaf loss, canopy stress, and bark decay. They also produce honeydew, a sticky secretion that leads to black, sooty mold and attracts other pests.
Though they favor the invasive tree-of-heaven, they also target maples, walnuts, willows, and fruit trees. While spotted lanternflies can defoliate trees and cause ongoing stress, they typically do not kill healthy trees. Their impact is considered more of a nuisance, especially in high numbers.
Signs of a spotted lanternfly infestation include gray, spotted adults or bright red-winged adults; sticky residue on leaves beneath trees; black sooty mold on bark or patios; and mud-like egg masses on bark, outdoor furniture, or firewood. To protect your trees, scrape and destroy egg masses from October to May. Capture nymphs using sticky bands—monitor traps to avoid harming beneficial insects. Avoid moving firewood or infested outdoor materials between locations. Act quickly to limit tree stress and reduce mess from honeydew and mold buildup.
When to Call a Certified Arborist
Early intervention is key. If you notice signs of either pest—or just want peace of mind—a certified arborist pest control expert can evaluate tree health and risk, recommend the right treatment (insecticides, pruning, and monitoring), identify which trees are at risk, create a proactive pest control plan, and help improve long-term tree health to reduce susceptibility.
Both pests act faster than many expect. A small population of bagworms can strip entire evergreens in a single season. Spotted lanternflies create lingering stress through sap extraction and secondary mold, gradually weakening trees and inviting further damage.
Seasonal timing also plays a vital role. Bagworms are best treated immediately after hatching in late June, while lanternflies are most vulnerable in egg or early nymph stages. Applying treatments during these windows improves outcomes and reduces repeated chemical use.
Tree species matter, too. Arborvitae’s dense structure makes it a bagworm magnet, reinforcing the need for routine arborvitae pest control. Spotted lanternflies prefer a wide range of hardwood and fruit trees. Knowing your trees helps prioritize monitoring.
While DIY options like scraping egg masses or removing bagworm cases can help, large infestations almost always require professional help. Misapplied treatments may harm beneficial insects—or your tree itself. Prevention is your best defense. Regular inspections, seasonal treatments, and healthy maintenance routines—like proper pruning and mulching—can keep your trees resilient, even in pest-prone environments.
Need Help?
We know trees—because we’ve been caring for them since 1978. Our team is ready to help you identify and treat emerging pest issues before they escalate. Contact Ahlum & Arbor to schedule a visit today.
