Diseases of Conifers UTAH PESTS In‐Service Training: Ornamental and Turf Pest Management February 3‐4, Provo, UT Marion Murray Conifer disease samples subdbmitted to plant pest diagnostic lab: 12% biotic Common conifers in the landscape jjpuniper: Rocky Mountain , Utah , Chinese spruce: blue, Engelmann , white, Norway fir: white, subalpine pine: western white, AAiustrian, lldodgepol e, ponderosa, 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 pure and/or dense plantings young vigorous trees Christmas tree plantations Foliar diseases Two infection courts for foliage diseases 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 • needles ttathat appear to have a “burnt” tip • needle drop Dothistroma management Remove fallen needles Plant resistant species (Scotch pine, 5‐needled pines, lodgepole pine, etc. ) Chemical: one application in June covering all needles (fixed copper, Bordeaux mixture) Spruce needle cast (Rhizosphaera kalkhoffii) Spruce needle cast Spruce needle cast management Remove as many fallen needles as possible Apply fungicide as preventative starting when new needles are half developed Bordeaux mixture chlorothalonil Elytroderma needle cast (Elytroderma deformans) Hosts: ponderosa pine Symptoms: red‐brown needles with green bases witches’ brooms Elytroderma Stem/Twig Diseases Rusts Basidiomycete Rusts are unique many need an alternate host to complete life cycle can have up to 5 different spore types biotrophs obligate parasites Life strategies of plant pathogens PARASITISM SAPROPHYTISM OBLIGATE FACULTATIVE FACULTATIVE OBLIGATE PARASITE SAPROPHYTE PARASITE SAPROPHYTE E parasite parasite, saprophyte, saprophyte X only but saprophyte but parasite only A occasionally occasionally M P RUSTS MOST WOOD YEASTS L POWDERY ROOT ROTS DECAY MOLDS E MILDEW FUNGI S Spruce broom rust (Chrysomyxa arctostaphyli) Alternate host is bearberry (Arctostappyhylos 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 (aecia) Win d and rain dlideliver to alternate host ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Only management option is cultural: prune Juniper broom rust (Gymnosporangium sp.) Hosts: Utah and Rocky Mountain junipers Symptoms: witches broom Alternate hosts: serviibceberry, hawthorn, mountain‐ash Juniper broom rust Infections on jjpuniper 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 GllGalls survive many years ‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Management: pruning Pinyon blister rust (Cronartium occidentale) Native pathogen of ppyinyon 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 infections occur through wounds, branch stubs: facultative parasite Cytospora canker Most common canker on conifers Facultative parasite 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 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 StSymptoms: reddduced vigor, lfleaf discol orati on, small ffitruit, 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 FiidFungicides Agri‐Fos, Fosphite, Phostrol: foliar or drench Aliette WD G: flfoliar; (non‐bearing c herry trees onl)ly) 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, pihitch oozing from base of tree ((if)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: Keep trees hlthhealthy 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: lodggpepole, pp,onderosa, ppyinyon , Douglas‐fir,,, white fir, 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 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 adltdult trees Ramorum blight • non‐oak hosts • spots and blotches on leaves & shoot die back • 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. ) 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 Provide optimal watering—not too much Heavy pruning each year before bud break can improve life span of tree.