Does one of your trees look a little under the weather? Let’s get you the guidance you need to figure out what might be going on.
How to use the
tree symptom decoder
- Figure out what kind of tree you have; knowing the general family or genus is enough to get you started. (Keep in mind, some unique tree varieties, called "cultivars", are specially grown to look a bit unusual or colorful on purpose.)
- Find the name of your tree on our list.
- Browse through the descriptions to see which signs match what you're seeing.
- Explore the trusted resources we’ve linked to guide your next steps!
Safe(tree) first
Before you apply any heavy chemical treatments or break out major tools, we recommend getting a second opinion from a pro.
Find your tree
Apple (Malus)
Chlorosis: Pale green to yellowish leaves
Fire Blight: Light brown to black leaves; dried fruit; water logged blossoms; dead 'shepherds crook' twigs and branches
Japanese Beetle: Brown to bronze and metallic green beetle with six white tufts of hair along hind sides of abdomen.
Oystershell Scale: A cluster of grey scales resembling rice along the bark and branches; sometimes settling near buds
Powdery Mildew: White powder-like substance on the upper and lower areas of the leaf
Ash (Fraxinus)
Ash Flower Gall Mite: Infested flowers become deformed and remain on trees as green masses until fall
Emerald Ash Borer: Adult is 1/2 inch long, narrow, metallic green beetle, D-shaped exit hole (1/8" diameter) found on trunk or branches *this insect has not been officially detected in Wyoming*
Leafcurl Ash Aphid: Leaves tightly rolled and thickened; white/waxy insects may be evident
Lilac/Ash Borer: Exit holes the size of a pencil eraser; usually found along branch crotches, branches, or the main stem; die-back may be evident
Oystershell Scale: A cluster of grey scales resembling rice along the bark and branches; sometimes settling near buds
Wood Boring Insects of Ash Trees: Major and minor wood boring insects of ash trees.
Aspen (Populus)
Aphids: Leaf curling, presence of ants or a sticky honeydew-like substance on the leaf
Bacterial Wetwood: Oozing liquid from wounds; yellow-brown discoloration of bark
Chlorosis: Pale green to yellowish leaves
Cytospora Canker: Orange oozing spores form along the main stems; girdling occurs on section of tree above the canker
Leaf Spots: Tan to black spots that develop on the leaf surface
Poplar Scale: A cluster of grey scales resembling rice along the bark and branches; sometimes settling near buds
Poplar Twiggall Fly: Presence of smooth, knot-like gall on tip of aspen twig; Cytospora Canker may develop around the gall
Powdery Mildew: White powder-like substance on the upper and lower areas of the leaf
Shoot Blight: Irregular brown/black spots form on leaf; infected shoots turn black and resemble a 'shepherd's crook'
Birch (Betula)
Bronze Birch Borer: Bronze colored insect borer; D-shaped exit holes along main stem and branches; Dieback of terminal branches
Oystershell Scale: A cluster of grey scales resembling rice along the bark and branches; sometimes settling near buds
Black Locust (Robinia)
Locust Borer: Insect is an inch long and very colorful (black body, yellow stripes, red legs); Dieback and knotty swelling may be evident
Boxelder (Acer negundo)
Aphids: Insects sucking on leaf surface, sticky leaf surface, flying insects around the canopy
Boxelder Bugs: Black 1/2" insects with red lines on thorax, orange/red eggs in clusters on leaf surface, usually found surrounding homes near south-facing windows
Buckeye/Horsechestnut (Aesculus)
Leaf Scorch: Burn appearance along margin of the leaf; can resemble leaf spots
Catalpa (Catalpa)
Verticillium Wilt: Rapid dieback or wilting of individual branches on tree; usually not the entire tree
Cherry (Prunus)
Aphids: Leaf curling, presence of ants or a sticky honeydew-like substance on the leaf
Cytospora Canker: Orange oozing spores form along the main stems; girdling occurs on section of tree above the canker
Japanese Beetle: Brown to bronze and metallic green beetle with six white tufts of hair along hind sides of abdomen.
Peachtree Borer: Presence of a wet spot or oozing, gummy sap along lower trunk
Chokecherry (Prunus)
Black Knot Disease: Black, swollen growths form along the branches and stems; galls may be covered with olive-green spores
Eastern Tent Caterpillar: White webbing present is thickly constructed in the forks and crotches of trees; the larvae do not feed within their webs, but congregate there at night and during rainy weather.
Eriophyid Mites: Leaves have finger-like protrusions growing on surface.
Fall Webworm: White webbing present in the branches and crown of the tree, and occur in summer and fall, whereas eastern tent caterpillars appear in spring.
Cottonwood/Poplar (Populus)
Bacterial Wetwood: Oozing liquid from wounds; yellow-brown discoloration of bark
Cytospora Canker: Orange oozing spores form along the main stems; girdling occurs on section of tree above the canker
Leaf Spots: Tan to black spots that develop on the leaf surface
Petiole-Gall Aphid: Swelling/thickening of the petiole which results in the formation of round galls
Poplar Scale: A cluster of grey scales resembling rice along the bark and branches; sometimes settling near buds
Powdery Mildew: White powder-like substance on the upper and lower areas of the leaf
Shoot Blight: Irregular brown/black spots form on leaf; infected shoots turn black and resemble a 'shepherds crook'
Crabapple (Malus)
Fire Blight: Light brown to black leaves; dried fruit; water logged blossoms; dead 'shepherds' crook' twigs and branches
Chlorosis: Pale green to yellowish leaves
Japanese Beetle: Brown to bronze and metallic green beetle with six white tufts of hair along hind sides of abdomen.
Powdery Mildew: White powder-like substance on the upper and lower areas of the leaf
Elm (Ulmus)
Bacterial Wetwood: Oozing liquid from wounds; yellow-brown discoloration of bark
Elm Leaf Beetle: Leaves are skeletonized; holes throughout leaves
Elm Leafminer: Tunnels made throughout the leaf surface
European Elm Scale: Scales group together on crotch of branches; scales are dark-red, purple, or brown surrounded by white wax fringe
Japanese Beetle: Brown to bronze and metallic green beetle with six white tufts of hair along hind sides of abdomen.
Oystershell Scale: A cluster of grey scales resembling rice along the bark and branches; sometimes settling near buds
Squirrel Damage: Squirrels tend to chew on buds and tree bark during winter months; may cause girdling around wounds
Hackberry (Celtis)
Eriophyid Mites: Branches/twigs deformed into a dense mass called "Witches Broom"
Hackberry Nipplegall: Leaves with large, raised bumps
Hawthorn (Crataegus)
Chlorosis: Pale green to yellowish leaves
Fire Blight: Light brown to black leaves; dried fruit; water logged blossoms; dead 'shepherds crook' twigs and branches
Pear Slug: Chewing/holes in leaves
Rusts: Orange/yellow spots on leaf surfaces
Honeylocust (Gleditsia)
Honeylocust Leafhopper: Spotty yellow foliage; can occur alongside Plant Bug infestation in late spring
Honeylocust Plant Bug: Dieback/twisted leaves; usually occurs on new growth
Honeylocust Podgall Midge: Leaflets swell to form galls; When maggots emerge, galls drop leaving bare branches
Honeylocust Spider Mite: Orange 1 mm mites usually found under bud scales/in bark cracks; Bronze dieback within foliage
Thyronectria Canker: Rust to Black colored fruiting bodies along dead areas of bark; Premature leaf drop
Juniper (Juniperus)
Cedar Apple Rust: Large galls develop on ends of branches; orange telial thorns form during rainy weather; dieback throughout tree
Juniper Spittlebug: White, frothy masses develop on needles
Spider Mites: Speckled leaf surface; plant appearance becomes bronze/gray; leaf scorch
Linden/Basswood (Tilia)
Japanese Beetle: Brown to bronze and metallic green beetle with six white tufts of hair along hind sides of abdomen. Primarily littleleaf lindens are of concern.
Leaf Scorch: Leaf spots; burn along margin of the leaf
Oystershell Scale: A cluster of grey scales resembling rice along the bark and branches; sometimes settling near buds
Maple (Acer)
Aphids: Leaf curling, presence of ants or a sticky honeydew-like substance on the leaf
Chlorosis: Pale green to yellowish leaves
Eriophyid Mites: Leaves display masses of pinkish patches
Japanese Beetle: Brown to bronze and metallic green beetle with six white tufts of hair along hind sides of abdomen.
Winter Sunscald: Sunken/discolored bark; cracked or sloughed off bark
Mountainash (Sorbus)
Fire Blight: Light brown to black leaves; dried fruit; water logged blossoms; dead 'shepherds crook' twigs and branches
Japanese Beetle: Brown to bronze and metallic green beetle with six white tufts of hair along hind sides of abdomen.
Oystershell Scale: A cluster of grey scales resembling rice along the bark and branches; sometimes settling near buds
Oak (Quercus)
Bullet Gall: Woody, round gall on branches
Chlorosis: Pale green to yellowish leaves
Squirrel Damage: Squirrels tend to chew on buds and tree bark during winter months; may cause girdling around wounds
Pine (Pinus)
Chlorosis: Pale green to yellowish needles
Diplodia Blight: Needle kill at tips of branches; needles yellow/brown in color
Dothistroma Blight: Needle drop/browning of needles; bare branches
Ips Beetle: Tunnels underneath bark; severe dieback present
Mountain Pine Beetle: Popcorn-like "pitch tubes" of resin along main trunk; flakes of bark lie on ground below tree canopy; yellow/red foliage
Pine Wilt Disease/Nematode: Primarily seen in exotic species, quick fading of color in leaves/needles within a few weeks to a couple of months leading to mortality of the tree.
Spruce (Picea)
Cytospora Canker: Orange oozing spores form along the main stems; girdling occurs on section of tree above the canker
Ips Beetle: Tunnels underneath bark; severe dieback present typically from the top of the tree downward.
Rhizosphaera Needle Cast: Loss of needles on innermost branches towards the bottom of the spruce; black spots on surface of needle
Spider Mites: Speckled leaf surface; plant appearance becomes bronze/gray; leaf scorch
Walnut (Juglans)
Thousand Cankers Disease: Yellowing and wilting leaves on single branches
Willow (Salix)
Bacterial Wetwood: Oozing liquid from wounds; yellow-brown discoloration of bark
Cytospora Canker: Orange oozing spores form along the main stems; girdling occurs on section of tree above the canker