Identifying and managing Christmas tree diseases, pests and other problems

Annosus root rot

(Heterobasidion root rot), Heterobasidion annosum

Signs and symptoms

• Declining leader growth
• Dark, irregular-shaped staining in the center of cut trees
• Dead trees near old stumps
• Small white mounds (fungus) on the bark near ground line

Where to look

• Fields after multiple rotations without stump removal
• Trees planted near stumps

Similar symptoms as:

• Other root and canker diseases
• Drought

Scouting

• Examine stumps of harvested and dead trees.

Management options

• Consider stump removal prior to replanting.
• Treat freshly cut stumps of healthy trees with borax (Sporax) to prevent infection by windborne spores.
• Plant resistant species.

Host susceptibility

• High susceptibility: Fraser fir, Noble fir
• Medium susceptibility: Grand fir, Douglas-fir
• Low susceptibility: Nordmann fir, Turkish fir

Management calendar

• Look for declining growth, yellowing, dead trees (most likely during moisture stress): mid-April through mid-December
• Examine stumps at harvest season: November
• Remove stumps: March through mid-July
• Treat stumps at harvest: mid-October through mid-December

Phytopthora root rot

Phytophthora spp

Signs and symptoms

• Reduced or stunted growth
• Poor color
• Root decay
• Bleeding basal cankers
• Dead branches first noticeable at the base of the tree

Where to look

• Low-lying areas with poor drainage

Similar symptoms as

• Other root diseases
• Drought

Scouting

• Cut the tree and check cambium for presence of canker.
• Dig roots and check for dark and rotten roots.
• Look for dead trees in field.
• Look for flagging branches.

Management options

• Replant with resistant species.
• Improve field drainage (e.g., tiling, ditches).
• Avoid sites with poorly drained soils.

Host susceptibility

• High susceptibility: Fraser fir, Noble fir, Shasta fir
• Medium susceptibility: Douglas-fir
• Low susceptibility: Grand fir, Nordmann fir, Turkish fir

Management calendar

• Look for dying, yellowing trees; trees with cankers: April through Mid-September
• Scout for especially off-color trees with dead branches and wet areas: April through Mid-September
• Plant resistant species: February through March
• Improve drainage: September through October

Grovesiella canker

Grovesiella abieticola

Signs and symptoms

• Pronounced cankers, often accompanied with overgrowth and thickening
• Cankers associated with off-color/dead branches on the tree
• Round, gray-black fruiting bodies (1.6 millimeters, produced by fungus) within the canker

Where to look

• On branches between dead and living wood
• Lower part of tree

Similar symptoms as

• Phytophthora root rot and stem canker
• Environmental stress
• Chemical damage

Scouting

• Search for slightly sunken dead tissue and cankers on dying branches.
• Look for overgrowth.

Management options

• Cut and destroy trees exhibiting symptoms.
• Do not replant near infected trees.

Host susceptibility

• High susceptibility: Shasta fir, White fir
• Medium susceptibility: Grand fir, Noble fir

Management calendar

• Look for dead branches with overgrowth (most likely during moisture stress): mid-March through mid-September
• Check off-color/dying branches: mid-April through mid-September
• Remove and destroy infected branches: April through mid-September

Interior needle blight

Several fungi species: Mycosphaerella spp., Phaeocryptopus nudus, Phyllosticta abietis, Toxosporium spp., Rhizosphaera

Signs and symptoms

• Random to complete browning of older needles, mostly on lower branches
• Symptomatic needles initially remain firmly attached to the branch
• Small, black fungal fruiting bodies present on the undersides of needles
• Limited to true firs

Where to look

• Older, dense trees
• Areas with poor air circulation

Similar symptoms as

• Environmental stress
• Drought
• Interior needle loss
• Nutrient imbalances

Scouting

• Observe trees in weedy, crowded sites.
• Observe areas near timber.

Management options

• Promote better air circulation within plantations.
• Improve weed control.
• Conduct basal pruning.
• Spray protective fungicides, if needed (multiple years).

Host susceptibility

• High susceptibility: Grand fir, Noble fir
• Low susceptibility: Fraser fir, Nordmann fir, Turkish fir

Management calendar

• Look for older needles dead but still attached: mid-August through mid-October
• Check lower branches: September through mid-November
• Use fungicides to protect new growth: mid-May through mid-July

Rhabdocline needle cast

Rhabdocline spp.

Signs and symptoms

Before bud break:

• Reddish-brown spots on upper surface of current-year needles; distinct border between diseased area and healthy green tissue
• Swollen, elongated, light-tan fruiting bodies on the underside of symptomatic needles

During bud break:

• Fruiting bodies rupture underside of needle, releasing a mass of spores.

Where to look

• Douglas-fir sources from east of the Cascades

Similar symptoms as

• Cooley spruce gall adelgid
• Swiss needle cast
• Douglas-fir needle midge
• Rust

Scouting

• Search for symptoms prior to bud break, in late winter or very early spring.
• Look for reddish-brown splotches on the upper needle surface. Only the newly emerging spring growth can become infected.

Management options

• At bud break, spray fungicide (if needed) to prevent infection.
• Remove and destroy severely infected trees prior to bud break.
• Plant resistant or tolerant tree varieties; avoid Douglas-fir from Rocky Mountain seed sources, unless tested.

Host susceptibility

• High susceptibility: Douglas-fir only

Management calendar

• Look for current needles with reddish-brown spots: mid-February through mid-June
• Check underside of needles for fruiting bodies: mid-February through mid-April
• Use fungicides to protect emerging needles: mid-April through June

Swiss needle cast

Phaeocryptopus gaeumannii

Signs and symptoms

• Parallel rows of tiny, black fruiting bodies on the underside of older needles
• Yellowing or mottling of infected needles
• Loss of interior needles; thin appearance of trees

Where to look

• Areas with poor air movement
• Field edges near Douglas-fir timber

Similar symptoms as

• Rhabdocline needle cast
• Cooley spruce gall adelgid
• Environmental stresses
• Nutrient imbalances
• Winter burn
• Drought damage

Scouting

• Using a hand lens, look for parallel bands of tiny, black structures (0.1 millimeter) arising from the stomates on the undersides of affected needles.
• Start scouting when trees enter their third growing season, beginning in May.
• Look at older needles in the lower part of the tree.
• Pay particular attention to trees that appear off-color or thin.

Management options

• Improve air circulation in fields.
• Spray protective fungicides (if needed) between bud break and 3.8 cm of new growth.
• Plant alternative tree species.
• Avoid planting field edges near timber.
• Remove and destroy heavily infected trees prior to bud break.

Host susceptibility

• Medium susceptibility: Douglas-fir only

Management calendar

• Look for older needles turning yellow, as well as fungal structures: mid-February through mid-July
• Check underside of needles for black fruiting bodies: March through mid-May
• Use fungicides to protect new growth: May through mid-June

Melampsora needle rust

Melampsora occidentalis

Alternate hosts: black cottonwood, aspen and hybrids of Populus spp.

Signs and symptoms

• Slight yellowing on infected newly emerging needles
• Cream to yellow fruiting bodies two weeks after initial symptoms
• Discolored areas become necrotic, and the needles shrivel and shed during the following four to six weeks.
• Severely damaged shoots become cankered and die.

Where to look

• Areas near overwintered, diseased leaves of poplar or other alternate hosts

Similar symptoms as

• Chemical damage

Scouting

• Watch for yellowing on newly emerged needles.
• Look for yellow-orange pustules in discolored areas of the needles.

Management options

• Spray protective fungicide (if needed) on developing shoots.
• Remove susceptible poplar hosts near Douglas-fir plantations.
• Select a less susceptible seed source.

Host susceptibility

• Medium susceptibility: Douglas-fir only

Management calendar

• Look for new needles with discolored areas: mid-April through mid-July
• Check underside of new needles for orange structures: May through mid-July
• Use fungicides to protect new growth: mid-April through mid-May

Pucciniastrum needle rust

Pucciniastrum goeppertianum

Alternate hosts: Vaccinium spp.

Signs and symptoms

• Possible yellowing areas on infected needles
• White, tube-like fruiting structures on the underside of infected needles

Where to look

• Trees near alternate hosts (Vaccinium spp. such as huckleberry, wild blueberry and cranberry)

Similar symptoms as

• Current season needle necrosis
• Uredinopsis needle rust

Scouting

• Observe trees in areas near alternate hosts.
• Look for yellowing (often banded) on current season needles.

Management options

• Remove and destroy alternate hosts near plantation.
• Spray protective fungicides (if needed) on new developing shoots.

Host susceptibility

• High susceptibility: Shasta fir, Noble fir
• Medium susceptibility: Grand fir

Management calendar

• Look for white, tube-like structures on the underside of infected needles: All year round
• Check for alternate hosts (Vaccinium spp.): mid-June through November
• Use fungicides to protect new growth: mid-May through mid-June
• Remove and destroy alternate hosts: mid-August through September

Uredinopsis needle rust

Uredinopsis pteridis

Alternate host: bracken fern

Signs and symptoms

• Yellowing blotches on the upper surface of needles
• Needles of any age vulnerable
• White, tube-like fruiting bodies on underside of needles

Where to look

• Trees near alternate host (bracken fern)

Similar symptoms as

• Current season needle necrosis
• Pucciniastrum needle rust

Scouting

• Observe trees in areas near alternate host (bracken fern).
• Look for yellowing (often banded) on current season needles.

Management options

• Remove and destroy all bracken ferns nearby. Pathogen depends on alternate host for survival.
• Spray protective fungicides (if needed) on developing fir shoots.

Host susceptibility

• Medium susceptibility: Grand fir, White fir, Shasta fir

Management calendar

• Look for yellowing blotches on upper surface of infected needles: All year round
• Check for tube-like structures on underside of needles: mid-April through September
• Use fungicides to protect new growth: mid-May through mid-June
• Control ferns with herbicides: mid-August through September

Twig aphid

Mindarus abietinus

Signs and symptoms

• Curled, twisted needles on current year’s growth
• Stunted needles
• Needle loss
• Black, sooty mold on stems, trunk and needles
• Presence of bees and/or yellow jackets

Where to look

• Localized areas in the field

Similar symptoms as

• Various aphid species

Scouting

• Monitor egg hatch by late April, using a hand lens (15x). Aphids have two distinct forms: stem mother is relatively large and bluish-gray; offspring is smaller, greenish-yellow and may be covered by a fine powdery wax.
• Scout for pale tan, oval eggs coated with wax.
• Use beating sheet or board to detect presence of adults.
• Listen for wasps and bees.
• Check for black soot on the ground.

Management options

• Encourage natural predators like lacewings, earwigs, lady beetles and their larvae, ants, predatory thrips, predaceous midges and parasitoids such as Aphidius spp.
• Apply insecticide after eggs hatch. Synthetic pyrethroids may cause outbreak of secondary pests, such as eriophyid mites, due to reduction of natural predators.

Host susceptibility

• High susceptibility: Balsam fir, Fraser fir
• Medium susceptibility: Grand fir, Noble fir
• Low susceptibility: White fir

Management calendar

• Look for needle distortion, stunting and loss: mid-May through mid-November
• Look for presence of adults: mid-March through June
• Spray insecticide (if needed): April through mid-August

Conifer root aphid

Prociphilus spp.

Alternate host: Ash tree (Fraxinus spp.)

Signs and symptoms

• General decline of trees and eventual death of the leader and branch tips
• Typically on 3- to 4-year-old trees
• Stunted young trees
• Ant activity around trunks and roots
• Clusters of white aphids on the roots

Where to look

• Localized areas in the field

Similar symptoms as

• Nutrient deficiencies
• Root problems

Scouting

• Scout for ants around the trunks and roots. (Prociphilus spp. feed directly on conifer roots and often are attended by ants. Ants may defend the aphid from natural enemies and move aphids around.)
• Dig trees and search for root aphids.

Management options

• Keep trees healthy and free of pests, disease and cultural problems.
• Obtain seedlings from nurseries that have no root aphids.
• Use available systemic insecticides.

Host susceptibility

• High susceptibility: Fraser fir, Noble fir
• Medium susceptibility: Grand fir, Douglas-fir
• Low susceptibility: Nordmann fir, Turkish fir

Management calendar

• Look for trees declining; drastic growth reduction: All year round
• Look for ants around trunks and roots: mid-April through July
• Spray insecticide (if needed): May through June

Conifer aphids

Cinara occidentalis and Cinara abietis

Signs and symptoms

C. abietis (Giant conifer aphid)

• Easily visible
• Found feeding on the upper stems of trees, causing stunted terminals and needle yellowing
• Typically attended by ants
• Typically congregating in large colonies

C. occidentalis

• More difficult to find because they spread out
• Often feed on 1-year-old foliage on branches; as damage progresses, foliage may yellow and appear shiny from honeydew
• Ants seldom present

Where to look

• Randomly in the field
• Black “soot” in leaders
• Areas with yellow jackets

Similar symptoms as

• Other aphids

Scouting

• C. abietis (Giant conifer aphid) can feed throughout the year; damage may be evident any time of year. Scout for aphids in the internodal openings along the upper leaders.
• C. occidentalis attracts wasps and yellow jackets in the summer as the honeydew becomes more prolific. Look for damaged foliage and black soot on the ground throughout the year. These aphids are harder to spot and are dispersed along branches.

Management options

• C. abietis (Giant conifer aphid): Control using localized treatments, including crushing colonies by hand.
• C. occidentalis: Control early to avoid significant foliage damage. Use labeled insecticides for spot treatments to protect populations of natural predators.

Host susceptibility

• High susceptibility: Grand fir, Noble fir
• Medium susceptibility: Nordmann fir, Turkish fir
• Low susceptibility: Douglas-fir

Management calendar

• Look for stunting of terminals (C. abetis); soot on lower branches and off-color (C. occidentalis): All year round
• Look for overwintering eggs: February through mid-April
• Look for adults: Mid-April through mid-November
• Spray insecticide (if needed): May through July

Balsam wooly adelgid

Adelges piceae (exotic pest from Europe)

• Signs and symptoms

• Yellow needles and premature needle loss
• Flat top or crooked terminal
• Gouting (swelling) around buds and internodes
• Stiff, inflexible trunk and swollen lateral branches
• White, cottony masses on trunk and large branches
• Dead shoots or branches

Where to look

• Localized areas in the field

Similar symptoms as

• Root problems
• Severe aphid damage

Scouting

• Scout at waist height for swollen areas (white, cottony masses) in branches and main trunk.
• Check flexibility of the upper stem.
• Look for poor growth of trees or affected trees that have lost flexibility in the upper stem.
• Examine stumps for reddish discoloration.

Management options

• Spray insecticides at high volume and pressure during the first generation crawler stage.
• If the adelgid is found, treat the field prior to bud break of the following season.
• Clear-cut infested blocks. Do not leave infested trees in the field, and avoid cutting during crawler activity.

Host susceptibility

• High susceptibility: Fraser fir, Balsam fir
• Medium susceptibility: Noble fir, Shasta fir
• Low susceptibility: Grand fir, Nordmann fir, Turkish fir

Management calendar

• Look for swollen branch nodes and terminals: All year round
• Check for eggs and cottony tufts: April through mid-May
• Check for crawlers, using a hand lens: mid-May through October
• Spray insecticide (if needed) at/near bud break: May through July

Cooley spruce gall adelgid (on Douglas-fir)

Adelges cooleyi

Alternate hosts: Picea spp. such as Colorado blue spruce and other spruces

Signs and symptoms

• Yellow spots on needles
• Needles with bends or crooks
• Small, white, cottony balls on the underside of needles or pepper-sized crawlers on new needles
• Premature needle drop

Where to look

• Current season needles

Similar symptoms as

• Rhabdocline needle cast
• Douglas-fir needle midge

Scouting

• Examine the underside of needles for overwintering nymphs that could be covered by white wax (cottony tufts).
• Control for two years before harvest to have damage-free needles.

Management options

• Remove any mature spruce or Douglas-fir that may be a source of infestation.
• Use sprays when the crawlers are present and before the cottony stage occurs.
• Spot spray where problem populations are localized.
• Note: In most cases low to moderate numbers of this pest will not require control(s).

Host susceptibility

• High susceptibility: Douglas-fir

Management calendar

• Look for yellow spots and distortion on needles: mid-January through mid-November
• Look for crawlers on new needles: April through mid-June
• Spray insecticide (if needed) before cottony stage: May through June

Douglas-fir needle midge

Contarinia spp.

Signs and symptoms

• Swollen, yellow needles where maggots are active
• After emergence of maggots, needles with possible reddish-brown appearance
• Premature needle loss

Where to look

• Sites with native Douglas-fir trees nearby

Similar symptoms as

• Rhabdocline needle cast
• Cooley spruce gall adelgid

Scouting

• By April, place emergence traps under the north side of previously infested trees.
• Place several traps per field; check frequently to detect and count the midges.
• Monitor for adult female midge emergence to effectively time spray applications.
• Check degree-day emergence models online.

Management options

• Encourage and protect natural predators.
• Remove heavily infested trees before larvae exit the needles in the fall.
• Base insecticide application on collection of adults in emergence traps or field scouting. Insecticides will be effective only against adults.
• Make first application as traps or weather dictate; often at bud swell to bud break.

Host susceptibility

• High susceptibility: Douglas-fir

Management calendar

• Look for swollen, yellow needles: June through December
• Place emergence traps: mid-March through mid-May
• Apply spray control measures based on monitoring: mid-April through mid-June
• Remove infested trees: August through mid-October

Spruce spider mite

Oligonychus uinunguis

Signs and symptoms

• Rusty or bronze colors near the base of the needles; damage possibly most severe during hot, dry weather
• Premature needle drop
• Damage heaviest at the bottom, inside of the tree
• Permanent chlorophyll loss
• Fine webbing at base of needles and twigs; cast skins, dead mites, dirt and other debris trapped in the silk

Where to look

• Localized areas in the field
• Along dusty roads and/or where other insecticides have been used

Similar symptoms as

• Eriophyid mites
• Environmental stress
• Aphids

Scouting

• Use a 15-20X hand lens to view spider mites and eggs. Eggs have a single, hair-like stripe on the top, which can be used to distinguish them from other spider mite eggs.
• Look for eggs during the winter and early spring (before April).
• Look for damage about halfway up the canopy and in the interior part of the tree.
• To detect active stages, beat suspect branches above collection tools, such as paper plates or any light-colored sheet or surface.

Management options

• Based on scouting, decide whether to control.
• If eggs are found in February or March, consider an application of horticultural oil.
• Miticides typically are applied in May or early June. Timing depends on scouting.

Host susceptibility

• High susceptibility: Fraser fir
• Medium susceptibility: Grand fir, Noble fir
• Low susceptibility: Douglas-fir

Management calendar

• Look for foliage yellowing and bronzing: mid-May through October
• Look for overwintering eggs: February through March
• Look for active mites: April through October
• Spray eggs (if needed): February through March
• Spray miticide (if needed) for adults/immature mites: May through June

Eriophyid mites

Trisetacus spp., Epitrimerus pseudotsuagae and Nelepella ednae

Signs and symptoms

• Bronzing and stunting of new needles, or bronzing and curling of more developed new shoots
• Needles later turn brown, die, and drop from the shoot, leaving naked branch tips

Where to look

• Localized areas in the field

Similar symptoms as

• Damage caused by environmental stress
• Other mites
• Chemical and nutrient imbalances

Scouting

• Look for needles at the branch tip that appear white-flecked or fuzzy when mite population is high.
• Check for clear to tan-colored eggs in clusters from late February through March.
• Check for active mites from late April through summer.

Management options

• Begin chemical control measures when new mites emerge (April to May) and again in the fall (October to November).

Host susceptibility

• High susceptibility: Noble fir
• Medium susceptibility: Grand fir, Douglas-fir

Management calendar

• Look for new needles bronzing and stunting: March through December
• Look for eggs: mid-February through mid-March
• Spray miticide (if needed) labeled for eriophyid mites: mid-March through May, September through mid-November

Root weevil

Otiorhynchus spp. and other species

Signs and symptoms

• Reduced plant growth
• Yellow needles and premature needle loss and/or root damage
• Scalloping or notching along needle margins
• Legless larvae grubs that bend their bodies in the shape of the letter “C”

Where to look

• New fields
• Field edges

Similar symptoms as

• Root problems
• Environmental stress

Scouting

• Monitor for adult weevils beginning in late May and early June, especially under needles, on cloudy days and in the evening.
• Scout for larvae on the roots of host plants April to May.

Management options

• At the first appearance of adults, apply chemical control and repeat.
• In the summer and fall, use habitat disruption practices such as disking or tilling, which may reduce populations.

Host susceptibility

• High susceptibility: Douglas-fir, Noble fir
• Medium susceptibility: Grand fir
• Low susceptibility: Nordmann fir, Turkish fir

Management calendar

• Look for notched needles: June through October
• Look for Larvae: April through May
• Look for adults June through September
• Use biocontrol: April through May
• Spray foliar insecticide (if needed): mid-June through mid-August
• Prepare the site: mid-August through mid-October

Douglas-fir twig weevil

Cylindrocopturus furnissi

Signs and symptoms

• Larvae bore through the bark to the wood surface. At maturity, they tunnel deeper, into the pith.
• As needles die, they turn reddish-brown.
• Dead twigs and branches, due to feeding damage
• Deformation of branches and poor growth (seen in Douglas-fir seedlings)

Where to look

• Dry sites with stressed trees
• Douglas-fir weakened by environmental stress or improper planting

Similar symptoms as

• Phomopsis canker
• Bark beetles
• Drought
• Winter damage

Scouting

• Scout for shoot dieback and feeding galleries on the surface of the wood.
• Look for 1.0 millimeter diameter adult weevil exit holes.
• Check on dead or dying twigs near the top of the tree.

Management options

• Target control, if needed, against emerging adults from July to August.
• Maintain vigorous growth by using proper cultural procedures.
• Remove and destroy infested trees.
• Avoid planting on dry sites.

Host susceptibility

• High susceptibility: Douglas-fir

Management calendar

• Look for dead branches: All year round
• Look for larvae bore through the bark: mid-January through April
• Watch for pupa stage: May through June
• Find adults: July through August
• Spray insecticide (if needed), targeting emerging adults: July through August
• Remove dead branches and trees: September through October

Interior needle loss

All Christmas tree species, especially noble fir

Causes

• Environmental stress, such as low light levels or moisture stress, can accelerate the yellowing and dropping of older needles.

Signs and symptoms

• Loss of interior, older needles
• Older needles turn yellow prior to shedding (late summer and early fall)
• Older needles easily shed from the stems

Where to look

• Interior/older needles

Management options

• Use mechanical shakers to minimize the problems on harvested trees.
• Use high-velocity air (leaf blowers) to remove unsightly needles.

Similar symptoms as

• Interior needle blight syndrome on noble and grand fir
• Other fungal needle casts

Yellow-green mottle syndrome

Douglas-fir

Causes

• Unknown

Signs and symptoms

• Yellow-green mottle syndrome on needles of all ages
• Initial symptoms after shoot elongation
• Yellow-green blotches may be small or cover the entire needle; midrib is never affected.
• Affected needles usually fall off the trees, sometimes causing severe defoliation.

Where to look

• Localized areas in the field with trees showing needle loss

Management options

• Do not spray; sprays are not effective.
• Give affected trees a chance to outgrow the mottling; trees sometimes outgrow the syndrome in two or three years.
• Remove and destroy trees that are affected every year.

Similar symptoms as

• Mite damage
• Nutrient deficiency
• Spray damage

Current season needle necrosis (CSNN)

Causes

• Unknown

Signs and symptoms

• Tan, discolored bands on random needles at the tip of or on the entire needle
• Affected portions turn reddish-brown, and may be shed if the entire needle is affected.
• Symptoms present on newly developed needles, often following high temperature events.
• Secondary organisms can colonize the necrotic tissue.

Where to look

• Valley sites and areas prone to high temperatures during shoot elongation

Similar symptoms as

• Needle rust
• Environmental stress

Management options

• Plant resistant species or sources.
• Shade trees during shoot elongation. Shading may reduce symptoms.
• Do not rely on spray treatments, which have shown limited benefit.
• Remove highly susceptible trees.

Scouting

• On noble fir, look for symptoms in upper part of the tree. Damage in other species can vary.
• Check for development of symptoms after high temperature events (over 85° F).
• Examine symptomatic needles during late summer and fall. Symptoms are present on all sides of the trees.

Host susceptibility

• High susceptibility: Grand fir, Noble fir
• Low susceptibility: Nordmann fir, Turkish fir

Management calendar

• Look for necrotic needles: All year round
• Check for symptoms, which commonly develop after high temperatures: mid-June through August
• Plant resistant species: February through April

Host susceptibility

• High susceptibility: Grand fir, Noble fir
• Low susceptibility: Nordmann fir, Turkish fir

Management calendar

• Look for necrotic needles: All year round
• Check for symptoms, which commonly develop after high temperatures: mid-June through August
• Plant resistant species: February through April

Frost damage

All Christmas tree species, especially early bud-breaking sources.

Causes

• Freezing temperatures in the spring when new growth has started to appear

Signs and symptoms

• Browning or wilting of new shoot growth
• Needles with a pale, water-soaked color or brown or red color, depending on degree of damage and species
• Frost-damaged foliage evident within a few days
• Some trees show damage, while others escape injury because of differences in bud break timing.

Where to look

• Trees that break bud early
• Low areas or frost pockets where cold air collects

Similar symptoms as

• Botrytis

Management options

• Do corrective pruning, if damage is severe. Even if damage looks severe when it first occurs, most trees are able to recover.
• Remove damaged growth during shearing.
• On frost-prone sites, cull or avoid some species/sources.

Winter injury

Any Christmas tree species, especially non-adapted seed sources or exotic species

Causes

• Cold temperatures, desiccation or formation of ice crystals within cells

Signs and symptoms

• Appears as damage to needles, bark and bud tissues
• Reddish-brown needles (when only needles are damaged)
• Death of buds or shoots (in severe cases)
• Symptoms may not be evident until warmer conditions later in spring.
• Injured plants cannot obtain water from frozen soil or move water through frozen tissues.

Where to look

• South to southwest side of the tree or on tissue above snow cover

Similar symptoms as

• Drought

Management options

• Carefully monitor sources adapted to extremely cold areas. They may experience winter injury or frost damage as they begin growth too soon in mild winters.
• Learn which locations and/or seed sources/species are more prone than others.

Drought

Causes

• Depleted soil moisture that lasts into the fall
• Late season planting that compromises root growth

Signs and symptoms

• Wilting of new growth, top dieback, tree death
• Loss of interior needles, shortened needles, needle tip dieback and overall slow growth
• Symptoms generally start at the top of the tree and continue downward.
• Damage may occur over several years

Where to look

• Newly planted trees
• Plants growing on gravelly or sandy soils

Similar symptoms as

• Root problems
• Winter damage

Management options

• To conserve water, eliminate competing vegetation with weed and brush control.
• Assess the type of soil where trees are going to be planted.
• Plant drought-tolerant species.
• Supplement irrigation as a last resort.
• Closely monitor trees weakened by drought because they are prone to other problems, especially insects and diseases.

Heat damage

Causes

• Extreme high temperatures and/or intense sunlight

Signs and symptoms

• Groups of needles on a shoot quickly turn reddish-brown.
• Entire tree appears burned/reddened due to late-season high temperatures that damage needles and shoots.
• Heat, drought and sunscald damage are closely related.

Where to look

• South or southwest side of the trees

Similar symptoms as

• Current season needle necrosis
• Mechanical damage
• Chemical injury

Management options

• Protect young seedlings using shade devices, such as shingles and cards.
• In older plantings, try to maximize soil moisture levels.

2, 4-D and triclopyr

True firs are more susceptible to these chemicals.

Causes

• 2,4-D and triclopyr are hormone-type herbicides used to control annual and perennial broadleaf weeds. These products are translocated throughout the plant.

Signs and symptoms

• Distorted plant parts, including twisting and curling on new growth
• Swollen shoot tips
• Severity of damage depends on amount applied, timing and other herbicides in the mixture.
• Damage also possible from drift of the herbicide

Where to look

• New growth is the most susceptible.

Similar symptoms as

• Shoot dieback

Management options

• Direct spray away from foliage. Use shields and low-drift nozzles.
• If using a chemical, follow label directions for the rate, timing and tree species.
• Calibrate application equipment properly.
• Avoid spraying on hot days. Amine forms are safer near trees.

Fertilizer burn

Causes

• Nutrient excesses, resulting from inappropriate or excessive fertilizer use, can damage or kill trees.

Signs and symptoms

• Reddish-brown discoloration or necrosis on the tips of newly developing needles
• All needles with similar levels of damage (unlike a fungal disease, in which only a few random needles are affected)

Where to look

• Damage pattern follows application area. Pay attention to newly planted seedlings and small trees.

Similar symptoms as

• Chemical injury

Management options

• Match fertilizer applications with tree growth and need.
• Time fertilizer application for the appropriate season (typically February to March).
• Calibrate applications.

Glyphosate (Roundup)

Causes

• Glyphosate is a nonselective herbicide that interferes with amino acid synthesis. It is translocated throughout the plant.

Signs and symptoms

• Applied prior to bud break: stunted new growth; short and pale green foliage
• Applied after bud break: rapid death of new needles; foliage with burned or desiccated appearance

Where to look

• Plants partially hit by sprays
• New growth

Similar symptoms as

• Botrytis

Management options

• Know spray timing and product options and usage. This information is critical.
• Carefully read all label instructions and precautions prior to purchasing and applying these herbicides.
• Avoid surfactants or combinations, which can increase tree damage.

Triazines

(atrazine, simazine, Velpar and others)

Douglas-fir and newly planted seedlings are more sensitive to damage

Causes

• Triazines are herbicides used to control grasses and some broadleaf weeds. These products are photosynthetic inhibitors.

Signs and symptoms

• Yellowing on needle tip and margin
• More pronounced damage with higher temperatures
• Light-textured soils prone to more damage

Where to look

• Newly planted container seedlings or sites with light-textured soils.

Similar symptoms as

• Current season needle necrosis

Management options

• Know spray timing and product options and usage. This information is critical.
• Carefully read all label instructions and precautions prior to purchasing and applying these herbicides.
• Apply lower product rates on light-textured soil.

Deer and elk

Damage from deer and elk is common on Douglas-fir in the spring, and on Fraser, Turkish and Nordmann fir in winter and spring.

Signs and symptoms

• Antler Rubbing: occurs on trees with open internodal spaces. Often bark is scraped off, producing long-lasting injury.
• Foliage Feeding: damage to leaders and upper branches, usually the current season foliage

Where to look

• Droppings and tracks around the base of trees aid in identification

Management options

• Fencing, repellents for individual tree protection.

Mice and voles

Signs and symptoms

• Small feeding marks around the stem of seedlings
• A decrease in tree growth from sublethal feeding injuries
• Tree death, if smaller trees completely girdled

Where to look

• Stems of seedlings, just above ground level, especially during winter and early spring

Management options

• Maintain weed control in the rows, particularly around the base of the tree; bare ground exposes rodents to predators.

Rabbits

Signs and symptoms

• Damage on young trees
• Shoots cut off at a 45-degree angle or girdling at the base
• Significant amounts of bark removed, or tree is completely cut.

Where to look

• Stems of young trees up to 2 ft from the ground

Management options

• Maintain weed control in the rows, particularly around the base of the tree. Use hazing, shooting, fencing and tree tubing.

Birds

Signs and symptoms

• Broken treetops (from May to July) when new tops are just elongating

Where to look

• Tall trees are most vulnerable.

Management options

• Place poles or perches throughout the fields at a height above the trees. Use frightening devices.

Mechanical damage

Causes

• Equipment and tools

Signs and symptoms

• Broken lower branches and areas of dead foliage where tires and equipment have run over or forced branches apart
• Bark/trunk damage (trees on row ends) that looks like cankers with dead branches above the damaged area
• Damaged foliage at a consistent height and side on rows where equipment has passed and exhaust fumes or heat have caused injury
• Split branch ends from dull shearing knives or cutting tools that do not cut cleanly. Branch ends to shatter and die.

Where to look

• Trees at row ends
• Lower branches; branches at equipment level

Similar symptoms as

• Vertebrate damage
• Drought

Management options

• Lay out field to leave enough space on row ends and between rows to allow for tractor turns and passage next to full-grown trees.
• Shield tractor tires and equipment to allow for passage between the rows.
• Minimize trips through the rows during bud break, as new growth is easily broken.
• Prevent prolonged contact of foliage with exhaust.
• Maintain sharp shearing and cutting tools to ensure well-cut branch ends.
• Use basal pruning, which can minimize lower branch damage.