New Hampshire

177 active alerts in this region

TreeIssues monitors plant and tree health threats across New Hampshire. Below you will find current alerts for pests, diseases, fungi, and invasive species that have been detected in the state. Alerts are sourced from USDA, USFS, and New Hampshire state agricultural agencies. Each alert includes severity ratings, affected species, symptoms, and recommended treatments.

Dutch Elm Disease

CRITICAL

Disease

A devastating vascular wilt disease spread by elm bark beetles that has killed millions of American elms since the 1930s. The fungus blocks water-conducting vessels, causing rapid wilting. It fundamentally changed the American urban landscape.

Affecting 45 regions

Chestnut Blight

CRITICAL

Fungus

A fungal disease that functionally eliminated the American chestnut as a canopy tree species in eastern forests by the mid-20th century. Once numbering in the billions, mature American chestnuts are now exceedingly rare. Root sprouts survive but are re-infected.

Affecting 25 regions

Fire Blight

HIGH

Disease

A bacterial disease that primarily affects members of the rose family, including apple and pear trees. It can destroy entire orchards in a single season. Bacteria spread rapidly during warm, wet spring weather through blossoms and wounds.

Affecting 32 regions

Beech Leaf Disease

HIGH

Disease

An emerging disease caused by a foliar nematode first identified in Ohio in 2012. It has spread rapidly through the native range of American beech. Affected trees can decline and die within 6-10 years. No effective treatment exists at scale.

Affecting 12 regions

Armillaria Root Rot

HIGH

Fungus

One of the most widespread and destructive forest diseases in the world, caused by a complex of honey mushroom species. It attacks stressed trees through root contact and can persist in dead stumps for decades, infecting nearby healthy trees.

Affecting 36 regions

Rhizosphaera Needlecast

HIGH

Fungus

A common fungal disease of spruce trees, especially Colorado blue spruce, throughout the Midwest and Northeast. The fungus infects current-year needles through stomata, causing them to turn purple-brown and drop prematurely. Inner and lower branches are affected first because humidity is higher there, and the disease progresses upward and outward over successive years. Severely affected trees may retain only the current year's needles at branch tips.

Affecting 25 regions

Cytospora Canker

HIGH

Fungus

A common fungal disease of spruce and other conifers that causes branch dieback, typically starting from the lowest branches and progressing upward. Colorado blue spruce and Norway spruce are especially susceptible. The fungus enters through wounds or stressed tissue. White resin bleeding on bark is a hallmark sign. Stressed trees are most vulnerable.

Affecting 25 regions

Verticillium Wilt

HIGH

Fungus

A soilborne fungal disease that affects hundreds of plant species including maples, elms, redbuds, and many other trees. The fungus invades through roots and colonizes the vascular system, blocking water transport. Symptoms often appear suddenly on individual branches. Maples are particularly susceptible. Olive-green to brown streaking in the sapwood is diagnostic.

Affecting 27 regions

Bronze Birch Borer

HIGH

Insect

A native North American wood-boring beetle that attacks birch trees, especially paper birch and European white birch in landscape settings. Larvae feed under the bark in a serpentine pattern, disrupting nutrient and water transport. Dieback starts at the top of the crown and progresses downward, the opposite pattern of many other pests.

Affecting 26 regions

New Hampshire

Dutch Elm Disease

Chestnut Blight

Fire Blight

Beech Leaf Disease

Armillaria Root Rot

Rhizosphaera Needlecast

Cytospora Canker

Verticillium Wilt

Bronze Birch Borer

Emerald Ash Borer

Hemlock Woolly Adelgid

Spongy Moth (formerly Gypsy Moth)

Japanese Beetle

Cedar-Apple Rust

Anthracnose

Apple Scab

Bronze Ground Beetle

Asian Longhorned Beetle Damages hardwood trees by tunneling deep into trunks and branches

Eastern Boxelder Bug

crown-tipped coral fungus

North American Luna Moth

Twice-stabbed Stink Bug

Dryad's Saddle

Conifer Mazegill

Chrome-footed Bolete

Yellow Patches

Pale Green Assassin Bug

Vermilion Waxcap

Monarch

Banasa calva

orange mycena

Spotted Tussock Moth

Snowy Urola Moth

Virginia Creeper Sphinx

Acanthocephala terminalis

hemlock varnish shelf

Reddish-brown Stag Beetle

Pseudomerulius curtisii

Blurry-spotted False Darkling Beetle

Red-rot Decay Stag Beetle

Waved Sphinx

Blinded Sphinx

Beggar Moth

Deceptive Snout

Cloaked Marvel

Wood Leopard Moth

Lettered Habrosyne Moth

Rosy Maple Moth

Red-headed Inchworm Moth

Pale Metanema Moth

Black-staining Polypore

Butterball

Eastern Black Trumpet

Painted Suillus

Red-mouth Bolete

Small-eyed Sphinx

Hebrew Moth

Maple Callus Borer Moth

Common Lytrosis Moth

Modest Sphinx

Salt Marsh Moth

Green Stink Bug

Virginia Ctenucha Moth

Banded Tussock Moth

Berkeley's Polypore

Frost's Amanita

Lynx Paw Oyster

Shaggy-fringe Lichen

Jackson's slender Caesar

Meadow Spittlebug

Red Milkweed Beetle

Broad-banded Eulogia Moth

Tufted Bird-dropping Moth

Northern Pine Sphinx

Pinnularia acrosphaeria

Nitzschia sigmoidea

Grapevine Beetle

Black-dotted Glyph

Scaly Chanterelle