Emerald ash borer is established in every Maryland county and has killed the large majority of Maryland's ash trees. The beetle's larvae feed beneath the bark in S-shaped galleries that cut off water and nutrient transport, killing trees within three to five years of infestation. Infested trees show dieback beginning in the upper canopy, bark splitting, and increased woodpecker activity. No treatment option exists for forest-grown ash at landscape scale. A cost-share program is available for chemical treatment of ash trees on public land and permanently protected land. For private forestland, salvage harvest of merchantable ash before value is lost, followed by reforestation with diverse native species, is the most productive response. Do not move firewood — EAB spreads most rapidly through the movement of infested wood.

Emerald Ash Borer Fact Sheet | EAB Cost-Share Treatment Program | Maryland EAB Long-Term Management Plan

Spotted lanternfly quarantine covers all 24 Maryland jurisdictions as of March 2026. The insect feeds on over 70 plant species including grapevines, fruit trees, and hardwood timber species, weakening trees through repeated feeding stress. It uses tree-of-heaven as its primary host. Controlling tree-of-heaven on your property reduces spotted lanternfly habitat and feeding pressure. Report sightings to the Maryland Department of Agriculture.

Spotted Lanternfly — Maryland Department of Agriculture

Hemlock woolly adelgid is established across Maryland and threatens eastern hemlock throughout the state. The greatest ecological impact is in western Maryland riparian areas, where hemlock canopy shades streams and moderates water temperatures critical to cold-water fisheries. Chemical treatment is effective for individual high-value trees if applied before infestation advances. Contact your local MFS office for site-specific guidance.

Hemlock Woolly Adelgid — University of Maryland Extension

Spongy moth causes periodic defoliation of oak and other hardwood species, primarily in western and central Maryland. Repeated defoliation weakens trees and contributes to mortality in combination with drought and other stressors. Egg mass surveys conducted annually by MDA inform response planning.

Spongy Moth Fact Sheet

Asian longhorned beetle is not currently established in Maryland but poses a significant threat to maple, birch, elm, ash, and other hardwood species. It has been detected in neighboring states. Report any suspect sightings immediately — early detection is the only effective management tool.

Asian Longhorned Beetle Fact Sheet

Beech leaf disease, caused by the foliar nematode Litylenchus crenatae, has been confirmed in Maryland and is spreading. It kills American beech through progressive canopy dieback over multiple seasons. No treatment is currently available at forest scale. Report suspect symptoms — dark banding between leaf veins, distorted or thickened foliage, premature leaf drop — to the Maryland Department of Agriculture.

Beech Leaf Disease — University of Maryland Extension

Invasive plants suppress native regeneration, expand rapidly following disturbance or timber harvest, and in some cases increase wildfire risk. Species active in every Maryland county include tree-of-heaven (Ailanthus altissima), Japanese barberry (Berberis thunbergii), multiflora rose (Rosa multiflora), oriental bittersweet (Celastrus orbiculatus), English ivy (Hedera helix), kudzu (Pueraria montana), mile-a-minute (Persicaria perfoliata), and Japanese stiltgrass (Microstegium vimineum). Early identification and active management — particularly following any canopy disturbance — are the most effective responses. Bamboo is also increasingly problematic on forest edges and riparian areas and warrants active management to prevent spread.

Multiflora Rose Fact Sheet | Oriental Bittersweet Fact Sheet | English Ivy Fact Sheet | Kudzu Fact Sheet | Mile-a-Minute Fact Sheet | Japanese Stiltgrass Fact Sheet | Bamboo Fact Sheet | Good Green: Land Manager's Guide