Hardwood Defoliators
Cankerworms
Eastern Tent Caterpillar
Forest Tent Caterpillar
Fall Webworm
Gypsy Moth
Large Aspen Tortrix
Leaf Galls
Leafminers
Loopers
Mourning Cloak
Orangestriped Oakworm
Skeletonizers
Tussock Moths
Uglynest Caterpillar
Walkingsticks

Softwood Defoliators
Jack Pine Budworm
Larch Casebearer
Needle Galls
Sawflies
Spruce Budworm
Tussock Moths

Hardwood Bark Beetles/Borers
Ambrosia Beetles
Asian Longhorned Beetle
Bark Beetles
Bronze Birch Borer
Carpenter Worm
Emerald Ash Borer
Powder Post Beetles
Red Oak Borers
Sugar Maple Borer
Two-lined Chestnut Borer

Softwood Bark Beetles/Borers
Engraver Beetles
Hemlock Borer
Horn-tails
Longhorned/Sawyer Beetles
Pine Root Collar Weevil

Hardwood Terminal Feeders
Aphids
Maple Petiole Borer
Oak Twig Pruner
Scale Insects
White Grubs

Softwood Terminal Feeders
Aphids/Spittlebugs
European Pine Shoot Beetle
Pales Weevil
Scale Insects
Shoot Moths
European Pine Shoot Moth
Spider Mites
White Grubs
White Pine Tip Weevil

Hardwood Sucking Insects
Aphids
Boxelder Bugs
Cicadas
Galls
Lacebugs
Scales

Softwood Sucking Insects
Aphids (adelgids, spittlebugs)
Balsam Woolly Adelgid
Eastern Spruce Gall Adelgid
Hemlock Woolly Adelgid
Scales

Insect Predators & Parasites
Biological Control Agents
Ants
Beetles (ladybugs, tiger)
Bugs
Dragon & Damsel Flies
Friendly Flies
Lacewings
Mantids
Wasps

Hardwood Leaf Diseases
Anthracnoses
Dutch Elm Disease
Maple Tar Spot
Oak Wilt
Septoria Canker
Wilts / Verticillium Wilt

Softwood Leaf Diseases
Needlecasts & Rusts
White Pine Blister Rust
Witches Brooms

Hardwood Stem/Branch Diseases
Armillaria
Aspen Shoot Blight
Ash Dieback
Beech Bark Disease
Black Knot of Cherry
Butternut Canker
Chestnut Blight
Dutch Elm Disease
Eutypella Canker
Hickory Decline
Hypoxylon Canker
Oak Wilt
Sapstreak in Sugar Maple
Trunk Rots
Verticillium Wilt

Softwood Stem/Branch Diseases
Cankers
Dwarf Mistletoe
Trunk Rots
White Pine Blister Rust

Hardwood Root Diseases
Armillaria
Cylindrocladium

Softwood Root Diseases
Annosum Root Rot
Damping-off Disease
Dye-Maker's Polypore
Tomentosus Root Rot

Other Biological
Beavers
Burls
Deer Browsing
Invasive Species
Mice
Nematodes
Pileated Woodpecker
Porcupines
Sapsuckers
Tree Age

Human Related
Herbicide Damage
Hydrological Damage
Pollution
Urban Splatter

Abiotic
Drought
Frost Cracking
Frost Damage
Lightning
Mechanical Damage
Scorch
Snow, Hail, & Ice
Wildfire
Wind
Winter Injury