Diseases of Conifers UTAH PESTS In‐Service Training: Ornamental and Turf Pest Management February 3‐4, Provo, UT
Marion Murray
Conifer disease samples submitted to plant pest b d l diagnostic lab: 12% biotic
Common conifers in the landscape
j p juniper: Rocky Mountain, Utah, Chinese y , ,
spruce: blue, Engelmann , white, Norway
fir: white, subalpine
pine: western white, Austrian, lodgepole, ponderosa, i hi A i l d l d pinyon, Scotch
Foliar Diseases
Foliage diseases of conifers On conifers, called “needle casts” Foliar diseases can affect healthy as well as stressed trees
trees planted in the wrong site p g pure and/or dense plantings young vigorous trees Christmas tree plantations h l
Foliar diseases Two infection courts for foliage diseases g
Direct penetration of cuticle, epidermis
Stomates: fungal mycelium or adaptive parts can find stomates "by feel"
Red band (Dothistroma septospora) Has a sexual (perfect) stage: Mycosphaerella pini In nature, only the pycnidia are found (imperfect stage)
Hosts: ponderosa, Austrian, pinyon (20 pine species)
Dothistroma symptoms • red bands around needles • brown needles that are green at the base eed es t at • needles that appear to have a “burnt” tip • needle drop
Dothistroma management Remove fallen needles Plant resistant species (Scotch pine, 5‐needled pines, lodgepole pine etc ) lodgepole pine, etc.) Chemical: one application in June covering all needles pp g (fixed copper, Bordeaux mixture)
Spruce needle cast (Rhizosphaera kalkhoffii)
Spruce needle cast
Spruce needle cast management Remove as many fallen needles as possible y p Apply fungicide as preventative starting when new needles are half developed
Bordeaux mixture chlorothalonil
Elytroderma needle cast (Elytroderma deformans)
Hosts: ponderosa pine p p Symptoms: red‐brown needles with green bases
witches’ brooms
Elytroderma
Stem/Twig Diseases
Rusts Basidiomycete y Rusts are unique
many need an alternate host to complete life cycle can have up to 5 different spore types biotrophs p obligate parasites
Life strategies of plant pathogens
PARASITISM
E X A M P L E S
SAPROPHYTISM
OBLIGATE PARASITE
FACULTATIVE SAPROPHYTE
FACULTATIVE PARASITE
OBLIGATE SAPROPHYTE
parasite only
parasite, parasite but saprophyte occasionally
saprophyte, saprophyte but parasite occasionally
saprophyte only
MOST ROOT ROTS
WOOD DECAY FUNGI
RUSTS POWDERY MILDEW
YEASTS MOLDS
Spruce broom rust (Chrysomyxa arctostaphyli)
Alternate host is bearberry (Arctostaphylos y( p y urva‐ursi) ) Causes brooms to form due to prolific, short twigs Brooms loose needles in fall; refoliate; may die but rarely result in tree mortality Hosts: mostly Engelmann spruce, but also Norway, red, white, Sitka
Spruce broom rust
Spruce broom rust Sporulates in summer p (aecia) Wind Wi d and rain deliver d i d li to alternate host ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Only management option is cultural: prune
Juniper broom rust (Gymnosporangium sp.)
Hosts: Utah and Rocky y Mountain junipers Symptoms: witches broom Alternate hosts: serviceberry, Al h i b hawthorn, mountain‐ash
Juniper broom rust
Infections on juniper j p occur in fall (windborne) Juniper sporulates in late spring ‐‐‐‐‐‐‐‐‐‐‐‐‐ Management: pruning
Western gall rust (Endocronartium harknessii) One of the few rusts with no alternate host (autoecious) Hosts: lodgepole, ponderosa, mugo, Scotch lethal to seedlings; older trees tolerate damage
Western gall rust Succulent stems most susceptible Spores released in spring; moisture needed for infection G ll Galls survive many years i ‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Management: pruning
Pinyon blister rust (Cronartium occidentale) Native pathogen of p y p pinyon pines Alternate host is Ribes sp. Symptoms: • galls • cankers • pitch masses
Pinyon blister rust (Cronartium occidentale)
Pinyon blister rust Infections on pine occur in fall; pine sporulates in spring ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Management: pruning
Cytospora canker (Cytospora sp.) Cankers:
localized bark/cambium necrosis stems, branches or twigs
sunken discolored with callus tissue sunken, discolored, with callus tissue
infections occur through wounds, branch stubs: facultative parasite
Cytospora canker Most common canker on conifers Facultative parasite p
Canker management Management y
prevent wounding
y
maintain tree health with optimal watering and fertilization
y
remove all dead or diseased branches and limbs
y
if canker is on main stem and small and new, cut diseased y tissue away with sterile tools
Root Rots
Crown and collar rot (Phytophthora sp.) P. cactorum, P. megasperma, P. cambivora, and others Hosts: most conifers; junipers Symptoms: reduced vigor, leaf discoloration, small fruit, S t d d i l f di l ti ll f it oozing cankers at the base of the tree, discolored inner bark, death
Phytophthora
Phytophthora life cycle
Phytophthora management Prevent overwatering Make sure soil is well‐drained F Fungicides i id
Agri‐Fos, Fosphite, Phostrol: foliar or drench
Aliette WDG: foliar; (non‐bearing cherry trees only) l G f l ( b h l )
Ridomil (metalaxyl) soil drench around on entire root zone
Armillaria root rot (Armillaria ostoyae) Hosts: hundreds of species; most conifers Symptoms: off‐color or brown foliage, stunted growth, pitch oozing from base of tree (conifers), sunken i h i f b f ( if ) k cankers covered with loose bark (hardwoods); dieback, death
Armillaria rhizomorphs
Armillaria mycelial fan
Armillaria honey mushrooms
Armillaria honey mushrooms on hardwood tree
Armillaria management Prevention is best tactic:
K Keep trees healthy t h lth
Avoid over‐irrigating
If trees are infested, remove soil and bark from base of tree and allow to dry to kill the mycelium
Do not plant in infested sites
Remove infested trees and neighboring trees
Schweinitzii crown rot (Phaelous schweinitzii) Hosts: all conifers Symptoms: few (decline) to none Decay fungus—leads to brown rot of heartwood
Schweinitzii crown rot
Black stain (Leptographium wageneri)
hosts: lodgepole, ponderosa, pinyon, Douglas‐fir, white fir, g p ,p ,p y , g , , western white pine
spreads via root to root contact, or by root feeding weevils or bark beetles
can be a problem in disturbed sites and/or on stressed trees
Black stain a wilt disease; fungi clog xylem vessels staining caused by hyphae and discoloration of tracheid cells
Black stain hyphae in xylem
Black stain
Diseases to Watch
Pine wilt Caused by the native pine wood nematode (Bursaphelenchus xylophilus) Transmitted by pine sawyer beetles (Monochamus)
Pine wilt A native pathogen; primarily a problem on non‐native pines (Austrian, scotch, Japanese black and red, Swiss stone)
Thousand cankers disease
Sudden oak death (Phytophthora ramorum ) Over 45 susceptible hosts, and 75 associated hosts 45 p , 75 Most of the outbreak in central coastal California Utah bans import of certain hosts from west coast nurseries
Two distinct diseases Sudden Oak Death • • • •
red oaks, beech, and tanoak stem lesions beneath the bark girdle and kill tree cankers often bleed or ooze can kill adult trees kill d lt t
Ramorum blight g • • • •
non‐oak hosts spots and blotches on leaves & shoot die back can kill juvenile plants usually not lethal for mature can kill juvenile plants, usually not lethal for mature plants spreads the disease
Sudden oak death Risk of sudden oak death based on P. ramorum climate matching and hardwood forest density in the USA
Risk Group III Risk Group II
Risk Group I
Leaf Drop/Scorch/Bacterial Disease of Chitalpa
Desert willow (Chilopsis sp.) x southern catalpa (Catalpa sp.) sp ) zone 6‐8
Leaf Drop/Scorch/Bacterial Disease of Chitalpa
Possible cause: Xylella fastidiosa; if not, abiotic causes Symptoms:
typical leaf scorch and spotting in mid‐summer leaf drop and refoliation yellowing dieback, decline
Leaf Drop/Scorch/Bacterial Disease of Chitalpa
Leaf Drop/Scorch/Bacterial Disease of Chitalpa
Very little to be done; antibiotics do not help y ; p Provide optimal watering—not too much Heavy pruning each year before bud break can improve life span of tree
