Growing Healthy Christmas Trees Nancy F. Gregory Plant Disease Diagnostician Delaware Cooperative Extension University of Delaware Plant Diagnostic Clinic Newark, DE http://extension.udel.edu
General Considerations Healthy Seedlings Choose the type of evergreen New types, cultivars Douglas fir, true firs Choose the site Level Soil Drainage Soil test for fertility, ph, etc. Planting Density Weed Control increase air circulation, drying
General Drought can look like disease browning, curling at the top. Young trees are more susceptible. Control weeds that compete for water Winter injury cold and wind Young trees more susceptible Symptoms are needle drop and scorching Wet weather this past year fluctuating Watch for decline that may indicate root rot Off color Phytophthora root rot in saturated soils Disease patterns on lower branches, north side, in field
Needlecasts and Needle Blights, Douglas-fir Rhabdocline Needlecast Swiss Needlecast* Pines Redband Needle blight Dothistroma Lophodermium needlecast Needle rust Rusts Spruce Firs Rhizosphaera needlecast Stigmina needlecast Needle Rust Rhizosphaera needlecast
Needles Needlecasts Rhabdocline Swiss Twig Blights Botrytis Diplodia Root Rots Phytophthora spp. Douglas Fir
Douglas Fir Rhabdocline needlecast Low lying areas, humid, shady areas, along tree lines mature trees Caused by a fungus Yellow spots on current year s growth in September or October Can t accurately diagnose then watch
Rhabdocline Brown bands on infected needles in Spring Second year needles On lower branches
Rhabdocline Bands split open longitudinally Fruiting bodies release spores from May to July during periods of wet weather Spores are wind-borne Spores infect young expanding needles Scout in Spring, spray at bud break, every 10 days
Rhabdocline Life Cycle Oct Nov Dec Jan Feb Mar Apr May Jun Jul
Swiss Needlecast on Douglas Fir Biggest problem in Delaware (Phaeocryptopus gaumannii) Brown tips on 2 3 year old needles on lower branches yellowing in fall Mottled look, no distinct margin between healthy and diseased To ID, look for black fruiting bodies in rows along stomates (on undersides of yellowing needles) Photos by Tracey Olsen
Swiss Needlecast
Swiss Needlecast Needle drop in late summer. Windborne spores infect young needles during wet weather. Fungicide when new shoots are 3/4 inch long (end of April into May) Spray again 10-14 days later 3 sprays
Swiss Needlecast July Tracey Olson
Rhabdocline Plus Swiss April Tracey Olson
Other on Douglas Fir Unknown needle spots Tip blights Sirococcus blight Image B Watt, U of Maine
Botrytis Blight
Diplodia (Sphaeropsis) Blight
Douglas Fir Needle Midge
Spruce Needles Rhizosphaera Needle Blight Stigmina Needlecast Spruce Needle Rust Twigs Diplodia Sirococcus Roots Phytophthora Root Rot
Rhizosphaera Needle Blight On spruce (and fir) Yellowing needles turn purple brown in late Summer 2 year old needles are affected on lower branches on trees Trees over 4 years
Rhizosphaera Needleblight Fruiting bodies along stomates on undersides of needles in late Summer or early Spring
Spores may infect new foliage from April to October (during wet weather) Apply fungicide when needles are half elongated and again in 2 weeks. Careful with chlorothalonil on Picea pungens affects blue color Rhizosphaera
Stigmina Needlecast Stigmina fruiting bodies are fuzzy On second year needles Rhizosphaera fruiting bodies not fuzzy
Rhizosphaera on spruce Two cycles of infection in the same year! Current year needles infected in spring may develop symptoms by late summer. Pycnidia form in August September Release conidia - infect uninfected current-year needles. Current year needles infected in spring then drop leaving bare spots in tree. Spray recommendations April/May to July 3 sprays
Rhizosphaera Life Cycle Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Tracey Olson
Flyspeck (may be confused as a needle cast) Stomiopeltis sp. Blue spruce vs. Rhizosphaera Needlecast vs. Swiss Needlecast Douglas fir
Fir Concolor, Fraser, Noble, Canaan Rhizosphaera Winter Damage Root Rot - Phytophthora
Canaan Fir Thrips Scirtothrips
Phytophthora root rot Young trees, low areas, poor drainage, stress
Phytophthora root rot Treatment if positively diagnosed, drench with subdue MAXX, alternate with Aliette
Pine Lophodermium needlecast On Pinus spp. especially seedlings Scotch most susceptible Spores - infection period in mid-late summer
Dothistroma Needle Spot Red Band Needle Blight Found in DE on Austrian pine and loblolly pine Control copper mid-may, again 4 weeks later
Pine Needle Rust Coleosporium rust Alternate hosts are aster and goldenrod Control aster and goldenrod weeds
Good Practices General Control Scout - Work in healthy areas first Don t shear in wet weather. Shear all known clean trees first. Clean pruners with alcohol or bleach Sanitation clean up needles that have dropped (mow with bag attached) Remove severely affected trees early, when dry Weed Control, air circulation
Diagnosis General Control Remember! Fungicides are preventative, they don t cure infections. Scout early! Fungicides Chlorothalonil (Bravo; Bravo Weather Stik; Chloronil; Daconil; Manicure; Echo; Pegasus; Concorde) Others - sterol-inhibiting fungicides, have been tested - are not effective and cost more! Fir mancozeb can be used, some phytotoxicity with chlorothalonil Must be labeled Timing - Rainfall problematic
Fungicides General Control 100 gal/acre volume coverage important - After finding a particular disease and having it identified, it may take 2 years to get it under control! Keep up your scouting and sprays find hot spots early Block planting and harvesting may not work in chose and cut