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Diseases of ConifersUTAH PESTS In‐Service Training: Ornamental and Turf Pest Management
February 3‐4, Provo, UT
Marion Murray
Conifer disease samples b d lsubmitted to plant pest
diagnostic lab:
12% biotic
Common conifers in the landscape
juniper: Rocky Mountain, Utah, Chinesej p y , ,
spruce: blue, Engelmann , white, Norway
fir: white, subalpine
i hi A i l d l d pine: western white, Austrian, lodgepole, ponderosa, pinyon, Scotch
Foliar DiseasesFoliar Diseases
Foliage diseases of conifers
On conifers, called “needle casts”
Foliar diseases can affect healthy as well as stressed treestrees planted in the wrong site p gpure and/or dense plantingsyoung vigorous treesh lChristmas tree plantations
Foliar diseases
Two infection courts for foliage diseasesgDirect 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 piniIn nature, only the pycnidia are found (imperfect stage)
Hosts: ponderosa, Austrian, pinyon (20 pine species)
Dothistroma symptoms
• red bands around needles
• brown needles that • brown needles that are green at the base
• needles that eed es t atappear 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 possibley p
Apply fungicide as preventative starting when new needles are half developedare half developed
Bordeaux mixturechlorothalonil
Elytroderma needle cast (Elytroderma deformans)
Hosts: ponderosa pinep p
Symptoms: red‐brown needles with green bases
witches’ brooms
Elytroderma
Stem/Twig DiseasesStem/Twig Diseases
Rusts
Basidiomycetey
Rusts are unique many need an alternate host to complete life cyclemany need an alternate host to complete life cyclecan have up to 5 different spore typesbiotrophspobligate parasites
Life strategies of plant pathogens
PARASITISM SAPROPHYTISMSAPROPHYTISM
OBLIGATEPARASITE
parasite
FACULTATIVEPARASITE
saprophyte
FACULTATIVESAPROPHYTE
parasite
OBLIGATESAPROPHYTE
saprophyte E parasite only
saprophyte, but parasite occasionally
parasite, but saprophyte occasionally
saprophyte only
EXAMPPLES
RUSTSPOWDERY MILDEW
MOST ROOT ROTS
WOOD DECAY FUNGI
YEASTSMOLDS
Spruce broom rust (Chrysomyxa arctostaphyli)
Alternate host is bearberry (Arctostaphylos urva‐ursi) y ( p y )
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 summerp(aecia)
Wi d d i d li Wind and rain deliver to alternate host
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
Only management option is cultural: prune
Juniper broom rust (Gymnosporangium sp.)
Hosts: Utah and Rocky yMountain junipers
Symptoms: witches broom
Al h i b Alternate hosts: serviceberry, hawthorn, mountain‐ash
Juniper broom rust
Infections on juniper j poccur in fall (windborne)
Juniper sporulates in late springlate spring
‐‐‐‐‐‐‐‐‐‐‐‐‐
Management: pruning
Western gall rust (Endocronartium harknessii)
One of the few rusts with no alternate host alternate host (autoecious)
Hosts: lodgepole, ponderosa, mugo, Scotch
lethal to seedlings; older trees tolerate damagetrees tolerate damage
Western gall rust
Succulent stems most susceptiblesusceptible
Spores released in spring; moisture spring; moisture needed for infection
G ll i Galls survive many years
‐‐‐‐‐‐‐‐‐‐‐‐‐‐
Management: pruning
Pinyon blister rust (Cronartium occidentale)
Native pathogen of pinyon pinesp y p
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 fall; pine sporulates in spring
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
Management: pruning
Cytospora canker (Cytospora sp.)
Cankers: localized bark/cambium necrosis stems, branches or twigs
sunken discolored with callus tissuesunken, discolored, with callus tissue
infections occur through wounds, branch stubs: facultative parasiteparasite
Cytospora canker
Most common canker onconifersconifers
Facultative parasitep
Canker management
Managementprevent woundingprevent wounding
maintain tree health with optimal watering and fertilization
remove all dead or diseased branches and limbs
if canker is on main stem and small and new, cut diseased tissue away with sterile toolsy
Root RotsRoot Rots
Crown and collar rot (Phytophthora sp.)
P. cactorum, P. megasperma, P. cambivora, and others
Hosts: most conifers; junipers
S t d d i l f di l ti ll f it Symptoms: reduced vigor, leaf discoloration, small fruit, 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 i idFungicidesAgri‐Fos, Fosphite, Phostrol: foliar or drench
l G f l ( b h l )Aliette WDG: foliar; (non‐bearing cherry trees only)
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, i h i f b f ( if ) k pitch oozing from base of tree (conifers), sunken
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 t h lthKeep trees healthy
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 treesRemove 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 heartwoodbrown 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 fungi clog xylem vessels
staining caused by hyphae and discoloration of tracheid cells
Black stain hyphae in xylem
Black stain
Diseases to Watch 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 hosts45 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 tanoakred oaks, beech, and tanoak• stem lesions beneath the bark girdle and kill tree• cankers often bleed or ooze
kill d lt t• can kill adult trees
Ramorum blightg• 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 )(Catalpa sp.)
zone 6‐8
Leaf Drop/Scorch/Bacterial Disease of Chitalpa
Possible cause: Xylella fastidiosa; if Possible cause: Xylella fastidiosa; if not, abiotic causes
Symptoms: typical leaf scorch and spotting in mid‐summerleaf drop and refoliationleaf drop and refoliationyellowingdieback, decline
Leaf Drop/Scorch/Bacterial Disease of Chitalpa
Leaf Drop/Scorch/Bacterial Disease of Chitalpa
Very little to be done; antibiotics do not helpy ; p
Provide optimal watering—not too much
Heavy pruning each year before bud break can improve life span of tree