Tree & Insect Directory
Identify common trees and insect pests in Colorado's mountain environment
Colorado Blue Spruce
Colorado's state tree with striking blue-gray needles and excellent cold hardiness.
Evergreen ConiferDouglas Fir
Large conifer with soft needles and distinctive cones with three-pointed bracts.
Evergreen ConiferEngelmann Spruce
High-elevation spruce with bluish-green needles and narrow crown.
Deciduous BroadleafGambel Oak
Native scrub oak forming thickets, important wildlife habitat with good fall color.
Evergreen ConiferLodgepole Pine
Straight-trunked pine common in higher elevation forests, highly adapted to fire.
Evergreen ConiferPinyon Pine
Small, bushy pine producing edible pine nuts, adapted to dry, rocky sites.
Evergreen ConiferPonderosa Pine
Large, drought-tolerant pine with orange-brown plated bark and long needles.
Deciduous BroadleafQuaking Aspen
Iconic Colorado tree with white bark and golden fall color, known for its trembling leaves.
Evergreen ConiferRocky Mountain Juniper
Drought-tolerant evergreen with scale-like foliage and blue berry-like cones.
Evergreen ConiferSubalpine Fir
High-elevation fir with spire-like form, common at treeline.
Leaf Feeding Insects & MitesAphids
Small, sap-sucking insects that cause wilting, curling, yellowing, and stunted growth of leaves.
Fruit PestApple Maggot
A fruit fly species whose larvae tunnel through apple flesh, leaving brown meandering tracks.
Bark Beetles & Boring InsectsAsh Bark Beetle
A small, brown beetle that feeds on the inner bark of ash trees, causing extensive damage.
Gall Making Insects & MitesAsh Flowergall Mite
A tiny mite that causes the formation of galls on the flowers of ash trees.
Leafminers & NeedleminersAspen Leafminer
A tiny moth whose larvae create serpentine-shaped galleries in aspen leaves.
DefoliatorBagworm
A moth whose larvae live inside silken cases covered with bits of foliage, feeding on evergreens and deciduous trees.
Scale InsectsBlack Pineleaf Scale
An armored scale insect that feeds on pine needles and twigs with a hard protective shell.
DefoliatorBox Tree Moth
An invasive moth whose caterpillars skeletonize boxwood leaves and can girdle stems.
Nuisance PestsBoxelder Bug
Distinctive black and red insects that feed on boxelder trees and often invade buildings.
Leaf MinerBoxwood Leafminer
The larval stage of a tiny fly that tunnels between leaf surfaces, causing leaves to blister.
Piercing-Sucking InsectBoxwood Psyllid
A tiny sucking insect that feeds on young boxwood shoots, causing new leaves to cup outward.
Fruit PestCodling Moth
A common orchard pest whose larvae bore into apples and pears and feed around the core.
SawfliesConifer Sawfly
Insects known for their voracious appetite and ability to defoliate conifer trees.
Gall FormerCooley Spruce Gall Adelgid
Creates distinctive pineapple-shaped galls on spruce branch tips.
Leaf Feeding Insects & MitesCottonwood Leaf Beetle
A reddish-brown to black beetle that feeds on cottonwood leaves.
Leaf Feeding Insects & MitesCottony Maple Scale
A common insect pest producing white cottony egg sacs that affect maple and other hardwood trees.
Bark Beetles & Boring InsectsDouglas Fir Beetle
A bark beetle that primarily feeds on Douglas Fir trees but can also attack other conifers.
Parasitic PlantDwarf Mistletoe
A parasitic plant that infects pines and other conifers, robbing the host of water and nutrients.
Leaf FeederElm Leaf Beetle
Defoliating beetle that skeletonizes elm leaves. Both adults and larvae feed on foliage.
Leafminers & NeedleminersElm Leafminer
An invasive sawfly species that attacks elm tree leaves, causing extensive damage.
Nuisance PestsElm Seed Bug
A true bug native to Europe that feeds on elm tree seeds and can invade homes.
Invasive BeetleEmerald Ash Borer
Highly destructive invasive beetle threatening ash trees. D-shaped exit holes are key signs.
Gall Making Insects & MitesEriophyid Mite
Tiny microscopic pests that cause significant damage to plants, found on undersides of leaves.
Scale InsectsEuropean Elm Scale
A scale insect that infests elm tree leaves and branches, feeding on tree sap.
Piercing-Sucking InsectHemlock Woolly Adelgid
A sap-feeding insect forming white cottony masses at the base of hemlock needles.
Bark Beetles & Boring InsectsHoneylocust Borer
A metallic wood-boring beetle whose larvae feed on honeylocust trees.
Scale InsectsKermes Scale
A tiny scale insect that feeds on tree and shrub sap, producing bright waxy coverings.
Leaf Feeding Insects & MitesLeafhopper
Small, agile insects with a triangular shape and distinctive hopping motion that feed on plant sap.
Bark Beetles & Boring InsectsLilac-Ash Borer
An insect pest that feeds on the bark and twigs of ash trees and lilac shrubs.
Leaf Feeding Insects & MitesMealybug
Tiny, soft-bodied insects with a waxy, white cottony appearance that feed on plant sap.
Bark BeetleMountain Pine Beetle
Devastating bark beetle attacking pine trees throughout Colorado. Signs include pitch tubes and fading needles.
Scale InsectsOystershell Scale
An armored scale insect with a hard, circular shell-like covering that infests trees.
Leaf Feeding Insects & MitesPeach Tree Borer
A clearwing moth whose larvae feed on the inner bark of peach, plum, cherry, and apricot trees.
Leaf Feeding Insects & MitesPine Needle Scale
A small, round, armored insect that infests pine trees throughout North America.
Scale InsectsPinyon Needle Scale
An armored scale insect that feeds on pinyon pine sap, causing needle yellowing and drop.
Bark Beetles & Boring InsectsPinyon Pitch Mass Borer
A bark beetle that attacks Pinyon Pine trees, creating sticky pitch masses.
Gall Making Insects & MitesPinyon Spindlegall Midge
An insect whose larvae feed on new pine growth, causing distinctive spiral-shaped galls.
Tip Moths/Twig Borers & BeetlesPinyon Tip Moth
An insect pest whose larvae feed on developing pine cones and needles.
Leaf Feeding Insects & MitesPlant Bug
True bugs with piercing-sucking mouthparts that feed on plants.
Bark Beetles & Boring InsectsPoplar Borer
A clearwing moth native to North America commonly found in deciduous forests.
Gall Making Insects & MitesPoplar Budgall Mite
A tiny eriophyid mite that affects poplar tree growth and appearance.
Gall Making Insects & MitesPoplar Twiggall Fly
A gall-forming insect that causes poplars and cottonwoods to produce abnormal growths on twigs.
Gall Making Insects & MitesPoplar Vagabond Aphid
An aphid species that feeds on poplar tree leaves, typically green or brown.
Tip Moths/Twig Borers & BeetlesSouthwestern Pine Tip Moth
A pest that attacks pine trees in the southwestern United States.
Piercing-Sucking InsectSpider Mites
Tiny arachnids causing stippled, bronze foliage and fine webbing on stressed trees.
DefoliatorSpongy Moth
A defoliating moth formerly known as the gypsy moth that feeds voraciously on hardwoods.
Scale InsectsSpruce Bud Scale
A small insect pest that feeds on spruce needles, covered in white cottony wax.
Bark BeetleSpruce Ips Beetle
Targets stressed spruce trees, creating galleries under bark. Look for boring dust and pitch tubes.
Leafminers & NeedleminersSpruce Needleminer
A sawfly whose larvae create characteristic serpentine mines along spruce needles.
Leaf Feeding Insects & MitesStriped Pine Scale
An armored scale insect that feeds on pine tree sap, leading to yellowing and stunted growth.
Tip Moths/Twig Borers & BeetlesTwig Beetle
A small insect native to Europe that causes significant damage to Viburnum shrubs and trees.
Bark Beetles & Boring InsectsWalnut Twig Beetle
A tiny beetle that is a major pest of black walnut trees, tunneling into bark.
Bark Beetles & Boring InsectsWestern Balsam Bark Beetle
A bark beetle that attacks balsam fir trees in western North America.
Bark Beetles & Boring InsectsWestern Cedar Bark Beetle
A small black beetle native to North America that commonly attacks western red cedar trees.
Leaf Feeding Insects & MitesWestern Spruce Budworm
One of the most destructive defoliators of coniferous forests in western North America.
Boring InsectWhite Pine Weevil
A weevil pest of conifers that causes characteristic drooping of terminal leaders.
Scale InsectsWillow Scale
An armored scale insect that feeds on willow trees by sucking sap from twigs, branches, and leaves.
Bark BeetleZimmerman Pine Moth
Attacks pine trees, causing resin masses and branch dieback. Most common in stressed or landscape trees.
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