Tree pests and diseases: signs and what to do

First sign: Thin, noodle-like tubes of sawdust and waste (frass) sticking out of the trunk

Trees: Flowering dogwood, Eastern redbud, Crape myrtle, Young or stressed landscape trees and more

When: Several generations can occur in a year, and in warm areas the beetles may be active almost year-round.

First sign: Sticky, shiny drops on leaves, cars, patios and benches under the tree (honeydew)

Trees: Maples, Oaks, Crape myrtle, Linden and more

When: Mostly spring through early summer when new growth is soft, with some species active again in fall.

First sign: Perfectly round exit holes about the size of a dime in the trunk or branches

Trees: Maples (including red, silver, sugar, Norway), Boxelder, Elms, Willows and more

When: Adult beetles are active in summer and early fall.

First sign: Small cone-shaped bags hanging from branches, made of silk and bits of leaf or needle

Trees: Eastern red cedar, Arborvitae, Leyland cypress, Pines and more

When: Eggs overwinter in the bag on the tree and hatch in late spring.

First sign: Thinning leaves and dead branches at the top of the crown

Trees: Paper birch, Yellow birch, River birch (less often hit), Other birches

When: Adult beetles come out in late spring to summer.

First sign: Silky white tents in the forks of branches in spring

Trees: Wild cherry, Crabapple and apple, Plum and other fruit trees, Other members of the rose family

When: Eggs hatch in early spring about when buds open.

First sign: Thinning or dying branches in the top of the crown, often starting in the upper part of the tree

Trees: Green ash, White ash, Other true ash trees

When: Adult beetles fly in late spring and summer.

First sign: Loose, silky webs that enclose leaves at the ends of branches

Trees: Walnut and pecan, Hickory, Black cherry, Sweetgum and more

When: The webs show up from mid to late summer and into fall, depending on the region.

First sign: Small white, cottony tufts at the base of needles on the underside of twigs

Trees: Eastern hemlock, Carolina hemlock

When: The white tufts are visible on twigs for much of the year and are often easiest to spot in late winter and spring.

First sign: Pine tops or whole crowns turning yellow, then red-brown, often fast

Trees: Loblolly pine, Slash pine, Virginia pine, Eastern white pine and more

When: Adult beetles are active in the warm months and can produce several generations in a year in warm climates.

First sign: Leaves that look like lace because only the tissue between veins is eaten

Trees: Linden, Birch, Crape myrtle, Cherry and plum and more

When: Adult beetles are active in summer, roughly early summer through late summer, and feed in the heat of the day.

First sign: Pale, stippled spots on the top of the leaf

Trees: Sycamore and planetree, Hackberry, Oaks, Linden and more

When: Some species overwinter as eggs in leaf tissue.

First sign: Small bumps, spots, felt-like patches or pouches on the top or underside of leaves

Trees: Oaks (the most gall-prone group), Maples, Hackberry, Cottonwood and willows and more

When: Most galls start in spring, when insects or mites feed or lay eggs on fresh growth.

First sign: Blotchy or winding tunnels (mines) inside leaves or needles

Trees: Holly, Birch, Aspen, Elm and more

When: Many leafminers lay eggs shortly after leaves expand in spring.

First sign: Small, popcorn-shaped lumps of pitch (pitch tubes) on the trunk where beetles tried to enter

Trees: Ponderosa pine, Lodgepole pine, Limber pine, Whitebark pine

When: Adult beetles fly and attack in summer.

First sign: Browned, dead leaves at the tips of branches (called flagging)

Trees: Oaks, Maples, Dogwood, Young landscape and nursery trees and more

When: Periodical cicadas come out every 13 or 17 years, usually in late May or early June, when the soil warms to about 64 degrees F at 8 inches deep.

First sign: Groups of caterpillar-like larvae feeding together on needles or leaves

Trees: Pines, Spruces, Flowering dogwood, Oaks and more

When: Timing depends on the species.

First sign: Small bumps or crusty spots on bark or twigs that can be scraped off

Trees: Crape myrtle, Magnolia, Maples, Tulip poplar and more

When: Young scales, called crawlers, move in spring and early summer and are the easiest stage to treat.

First sign: Small pitch tubes (popcorn-sized blobs of resin) on the trunk where beetles entered

Trees: Loblolly pine, Slash pine, Virginia pine, Eastern white pine and more

When: The beetle can be active across many months in warm areas and produces several generations in a year.

First sign: Stippled (speckled) yellow or brown needles on spruce

Trees: Spruces (spruce spider mite), Honeylocust (honeylocust spider mite), Hemlock, Arborvitae and more

When: Spruce spider mites are cool-season mites.

First sign: Tan or buff, fuzzy egg masses on trunks, branches, rocks, fences and outdoor items in fall, winter and early spring

Trees: Oaks, Aspen, Birch, Linden and more

When: Eggs overwinter in masses.

First sign: Gray, tan egg masses with a mud-like coating on trees, stones, vehicles or outdoor items

Trees: Tree of heaven (a favorite), Maples, Black walnut, River birch and more

When: Eggs overwinter and hatch in spring.

First sign: Leaves that wilt and turn brown in late summer while still on the tree

Trees: Red oaks (such as northern red, scarlet, black, pin), White oaks (such as white, chestnut, bur), Other oaks that are stressed

When: Adults come out in spring or early summer.

First sign: Irregular tan, brown or black blotches on leaves, often along the veins

Trees: American sycamore, White oak, Bur oak, Flowering dogwood and more

When: It is most common in cool, wet spring weather as leaves open.

First sign: Thinning crown, small leaves and slow growth over several years

Trees: White oak, Northern red oak, Pin oak, Sugar maple and more

When: The rot works year-round underground.

First sign: Leaf edges that die and turn light brown, often with a dark reddish-brown band and a yellow border next to the green part

Trees: Red oaks and pin oaks (most affected), White oak, Red maple, Elms and more

When: Leaf browning usually shows in mid to late summer and into early fall.

First sign: Dark green bands between the veins of the leaves, best seen from below with sunlight behind the leaf

Trees: American beech, European beech, Other beech species

When: Banding is easiest to see in summer when leaves are fully open.

First sign: Rough, swollen, tumor-like growths on twigs and branches

Trees: Black cherry, Plums and other cherry trees, Other Prunus (stone fruit) trees and shrubs

When: Infection happens in spring on young growth during wet weather.

First sign: Sunken, flattened or swollen patches on a branch or trunk where the bark looks different

Trees: Maples, Oaks, Ash and elm, Poplars, cottonwood and aspen and more

When: Cankers can be seen all year.

First sign: Round, brown, woody galls on cedar twigs, from the size of a pea to a golf ball

Trees: Eastern red cedar, Apple and crabapple (not on our species list), Hawthorn (not on our species list)

When: Orange jelly-like horns show on cedar galls in spring after warm rain.

First sign: On spruce, a branch that dies back above a canker, often in an upward spiral

Trees: Colorado blue spruce (the most often hit), Other spruces and firs, Aspen and cottonwood, Many other stressed trees, including maple and birch

When: The fungus lives through winter in the cankers.

First sign: New shoots that stay short, turn brown and die in late spring or early summer

Trees: Austrian, Scots and mugo pine (the most often hit), Red pine, Ponderosa pine and other two- and three-needle pines, Stressed or older pines

When: Spores are released in late spring and early summer in wet weather and infect new needles and shoots.

First sign: Sudden wilting and yellowing of leaves on one branch, called flagging

Trees: American elm, Siberian elm (some resistance), Lacebark elm (more resistant)

When: Symptoms often show in late spring and summer.

First sign: Shoot tips that wilt, turn brown or black, and bend into a shepherd's crook

Trees: Bradford pear and other ornamental pears, Apple and crabapple (not on our species list), Hawthorn, quince and mountain ash (not on our species list)

When: Infection often starts at bloom in warm, humid or wet spring weather.

First sign: Large, shelf-like or bracket-shaped fruiting bodies (conks) on the lower trunk or at the root flare

Trees: Oaks, Maples, Honeylocust, Beech and more

When: Conks usually appear in summer and fall, often after wet weather.

First sign: Conks, brackets or mushrooms growing on the trunk or large limbs

Trees: Silver maple, Red maple, Northern red oak, White oak and more

When: Decay goes on all year inside the tree.

First sign: Sudden wilting of leaves, often reddish or brown, that stay on the branches

Trees: Sassafras, Redbay and swamp bay (not on our species list), Avocado (a crop host)

When: Wilting can show at any time of year in warm areas.

First sign: Irregular brown or reddish-brown dead patches along leaf edges and veins, a sign of anthracnose

Trees: Sycamore and London planetree (anthracnose), Maples (tar spot and other leaf spots), Ash, Oaks and more

When: Anthracnose is most active in cool, wet spring weather as leaves open.

First sign: Leaves that turn dull green, bronze or brown from the tips and edges inward and then drop early

Trees: Red oaks (such as northern red, pin, Shumard, water, willow), Live oaks, White oaks (more resistant)

When: Spring and early summer are the high-risk times for new infections, when sap beetles are active and fresh wounds attract them.

First sign: Yellowing, wilting or dwarfed leaves or needles, even when soil is wet

Trees: Flowering dogwood, Eastern white pine, Douglas fir, Leyland cypress and more

When: The pathogen is most active when soil is warm and wet.

First sign: Needles that fade to a dull gray-green or yellowish color, then turn brown

Trees: Scots pine (the most often hit; not in our species library), Austrian and Japanese black pine, Some other pines, including red and jack pine (less often), Eastern white pine (tends to be more resistant)

When: Symptoms can appear from midsummer to late fall.

First sign: White to gray, dusty or powdery coating on the top or bottom of leaves

Trees: Flowering dogwood, Crape myrtle, American sycamore, White oak and more

When: Usually shows from late spring through fall.

First sign: Needles that turn brown or purplish, then drop

Trees: Colorado blue spruce (the most often hit), Black Hills and white spruce, Norway spruce (less often), Rarely other conifers

When: Infection is mainly in spring, when new needles come out and the weather is wet.

First sign: A black, soot-like coating on the upper side of leaves, twigs or fruit

Trees: Crape myrtle, Maples, Southern magnolia, Tulip poplar and more

When: It shows up during the growing season when sap-feeding insects are active and honeydew builds up.

First sign: Bleeding cankers on the lower trunk: dark, sticky or tar-like sap oozing from the bark

Trees: Northern red oak, Pin oak, Coast redwood (carries the pathogen, rarely dies), Bigleaf maple (carries the pathogen, rarely dies)

When: Spread is linked to cool, wet weather.

First sign: Pale yellow-green spots on leaves in early summer

Trees: Norway maple, Sugar maple, Red maple, Silver maple and more

When: Infection happens in spring as leaves open.

First sign: Yellowing, then bronzing and sudden wilting of leaves in hot weather

Trees: Pecan and other fruit and nut trees, Many other broadleaf trees and shrubs (grasses are not affected)

When: It is most active in summer, when soil and air temperatures are high.

First sign: Yellowing and wilting of leaves in the upper crown, then dieback of branches

Trees: Black walnut

When: Crown dieback is easiest to see in summer when leaves should be full.

First sign: Sudden wilting and yellowing of leaves on one branch or one side of the tree

Trees: Red maple, Norway maple, Sugar maple, Japanese maple and more

When: Wilting often shows after leaves are fully open, commonly in late spring and summer, especially when hot, dry weather hits an infected tree.

First sign: Yellow or orange-bordered patches on branches or the trunk, often swollen

Trees: Eastern white pine, Sugar pine, Western white pine, whitebark pine and other five-needle pines, Currants and gooseberries (Ribes), which are the alternate host

When: Spores from currant and gooseberry leaves blow to pine needles in late summer and fall.

First sign: Thinning canopy and dieback that begin one to several years after digging or grading

Trees: Oaks, Maples and beech, Pines and hemlock, Hickory and tulip poplar and more

When: Damage happens when the work is done, but symptoms can take years to appear, often during dry summers.

First sign: Wilting, curling or drooping leaves during the day

Trees: Maples, Oaks, Beech and birch, Hemlock, spruce and pine and more

When: Summer and early fall are the usual times, but a dry winter can stress evergreens.

First sign: A long vertical split in the trunk, often on the south or southwest side

Trees: Maples, Honeylocust, Lindens, Sycamores and planetrees and more

When: Cracks form in winter, usually after a sharp drop in temperature, often following a sunny day.

First sign: Trunk that goes straight into the ground like a pole instead of flaring out at the base

Trees: Maples (especially Norway maple), Oaks, Linden and honeylocust, Pear and redbud and more

When: The roots grow all the time, but symptoms often show in mid to late summer.

First sign: Leaves that are cupped, twisted, puckered or curled, often on new growth

Trees: Maples, Ash and elm, Redbud and dogwood, Pines and more

When: Injury often appears within days or weeks of spraying in spring and summer, when plants are growing.

First sign: Leaves that turn pale yellow or light green while the veins stay dark green

Trees: Maples, Pin oak and red oaks, River birch, Bald cypress and more

When: Most visible in spring and early summer when new leaves come out.

First sign: A long strip of bark blown off, often in a spiral or straight line down the trunk

Trees: Oaks, Pines and fir, Tall hardwoods such as tulip poplar and sycamore, Pecan and hickory and more

When: Lightning strikes are most common in warm-season thunderstorms, though damage can appear right away or many months later.

First sign: Brown needle tips on evergreens, mostly on the side that faces the road

Trees: Maples, Pines, Spruces and firs, Arborvitae and hemlock and more

When: Salt goes on in winter, but the damage shows later.

First sign: Sunken, dry or cracked patches of bark on the south or southwest side of the trunk

Trees: Maples, Honeylocust, Lindens, Bradford pear and more

When: Damage happens in winter, when the sun warms the bark on a cold day and the temperature drops fast at night.

First sign: Neat rows of small holes drilled around the trunk or limbs, a sign of sapsuckers

Trees: Maples, Birches, Pines, Cherry and more

When: Sapsuckers often feed on trees in fall, winter and spring.