Perspectives on managing summer diseases, rusts, & tree cankers Kerik D. Cox Plant Pathology and Plant-Microbe Biology Section School of Integrative Plant Science Cornell University
Outline Summer diseases of apple Key diseases, challenges, & management Efficacy & timing of fungicides Efficacy of organic management options Tree decline concerns & management Nectria and Botryosphaeria canker diseases Phytophthora scion rot Winter injury
Summer Diseases of Apple Several diseases causing: leaf spots, fruit finish blemishes, & fruit rots from fruit maturation to post-harvest Begin with latent infections at petal fall to 10-14mm and later infections during summer rains until harvest
Summer Diseases of Apple Bitter rot (Colletotrichum) Fly Speck / Sooty Blotch Pinpoint apple scab Black rot (Botryosphaeria)
Summer Diseases of Apple: Leaf Spots Misc: Glomerella leaf spot, Frogeye leaf spots, Alternaria leaf spot: warmer regions Overwinters in wood lots and thinning mummies Frogeye leaf spot Glomerella leaf spot
Summer diseases are becoming problematic in eastern US Problematic in production regions & systems that have reduced summer fungicide covers Cool dry weather reduced the problem Rainy weather or overhead irrigation exacerbates the problem Organic: Latent infections from petal to summer > post-harvest symptoms Inoculum: coming in neighboring wood lots particularly from wild brambles
Summer disease management No major gene resistance available > cultivars differ in susceptibility Yellow skin cultivars more than red skin cultivars Sanitation can greatly reduce disease Cluster thinning 5 > 3 fruit Summer pruning and training systems that increase circulation Increased labor costs
Summer disease management Managed by single-site fungicide applications after petal (covers) Extended intervals 14-21 days: Disease forecasting (DAS) treat > accumulated leaf wetness http://newa.nrcc.cornell.edu/newamodel/sooty_bl otch
Summer disease management Single-site fungicides: highly effective & consistent (QoIs, SDHIs, DMI, & benzimidazoles) Multi-site fungicide captan: persistent, but weak, and more variable Biologicals: ephemeral, variable, & less effective in high pressure
Sooty blotch & fly speck trials: 3.1-acre planting site Empire and Jonagold - M.9/M.111 interstem (18-20 years old) Widely-spaced two tree plots
Sooty blotch & fly speck trials Fungicide treatments Dilute handgun application timed at 7-10 day intervals from TC- 2 nd cover or 14-21 days from 3 rd -7 th cover Alternated with effective protectant standards not to exceed max applications (4 applications)
Sooty blotch & fly speck trials How effective are conventional & biological fungicides relative to one another? Can single-site fungicides tell us anything about timing?
Sooty blotch & fly speck trials Single-site fungicides highly effective Wet fall of 2009: captan(msf) & biologicals ineffective
Sooty blotch & fly speck trials Flyspeck: captan & biological less effective in wet season
Sooty blotch & fly speck trials Primary ascospore infections occur PF to 2 nd cover
Sooty blotch & fly speck trials Sulfur & copper effective > single-sites effective with 2 apps
Summary points for sooty blotch & fly speck trials Single-site fungicides highly effective Primary infections at 1 st & 2 nd cover (10-24 days post petal fall) important timing Manage primary infections well need > minimal cover program? Organic options work best under low to moderate pressure with frequent application
Organic Sooty blotch & fly speck trials NY & New England organic growers were storing clean fruit but had latent infections of fly speck & sooty blotch. Could sanitation & or organic fungicides be effective? Pinpoint Apple Scab
Organic Sooty blotch & fly speck trials Sanitation (cluster thin. + pruning) > fruit rots, biological, LLS
Organic Sooty blotch & fly speck trials 2.4-acre planting site at Loomis farm in Geneva Fenced and surrounded by biofuel willow
Organic Sooty blotch & fly speck trials High density tall spindle system 3 x12 spacing (1210 trees/acre) established in 2012 Trained as a slender fruiting wall: future proof for new mechanical thinning technologies Planted to Pristine, Williams Pride, NovaEasygro, Crimson Crisp, Juliet, Modi, Topaz, Goldrush, NY-13 and NY-1211 on G.202 & CG.935
Organic Sooty blotch & fly speck trials Season long disease management: 3 treatment programs x 9 cultivars with 3 replications Apple scab resistant cultivars; susceptible to fly speck/sooty blotch and cedar apple rust
Organic Sooty blotch & fly speck trials Treatments (14-21 day intervals): 1. Advanced: Biological Double Nickel LC (Bacillus amyloliquefaciens strain D747) & Cueva (low MCE 1.8%, copper soap) 2. Minimal: Organic approved sulfur and high (28% MCE) organic copper fungicides 3. Untreated control Diseases: Fire Blight, Sooty Blotch/Flyspeck, & Cedar apple rust
Organic Sooty blotch & fly speck trials Both provide control of sooty blotch / fly speck under high-moderate disease pressure
Organic Sooty blotch & fly speck trials Cultivar & season impacts the effectiveness of Cueva + Double Nickel
Organic Sooty blotch & fly speck trials Cueva + Double Nickel more variable on highly susceptible cultivars in some years
Organic Sooty blotch & fly speck trials Untreated Cueva & Double Nickel 2014 Trial: Topaz
Organic cedar apple rust trials More consistent performance on cedar apple rust
Organic cedar apple rust trials Some seasonal cultivar influence on performance. Modi not shown complete resistance
Summary points for organic Sooty blotch & fly speck trials Organic approved fungicides can be effective in high disease pressure when applied repeatedly and timed appropriately Cultivar may dramatically influence disease control Biologicals more prone to variable performance, more pleasant for labor/consumers in orchards, but increased cost
Outline Summer diseases of apple Key diseases, challenges, & management Efficacy & timing of fungicides Efficacy of organic management options Tree decline concerns & management Nectria and Botryosphaeria canker diseases Phytophthora scion rot Winter injury
Tree decline concerns in eastern US 2010 to present: slow growing wood decay fungi infecting: Pruning wounds during wet weather in late summer/early fall Trees compromised after seasons of cold, roundup, or salt injury Crotch angles and other wounded tissues
Nectria and Botryosphaeria cankers Causal agent(s): Nectria cinnabarina & Botryosphaeria spp. Symptoms: Dark brown wilted shoots may crook & look like fire blight Don t turn as black as FB
Nectria and Botryosphaeria cankers Signs: Pink/salmon or black stromata filled with spores Disease cycle: Infection: late summer or fall by windborne spores infecting leaf scar or summer pruning wounds
Nectria and Botryosphaeria cankers Disease cycle: N. cinnabarina & Botryosphaeria spp. infect trees compromised by mild winter injury, shoot blight, herbicide damage, hailstorms, stem borer, or deer browsing in wet seasons Survive quiescently in cankers, nursery stock, infected spurs, or pruning's on orchard floor
Nectria and Botryosphaeria cankers Management: Difficult > fungi protected deep in woody tissue Neonectria galligena = aggressive pathogen (wood decay fungus) in Europe Apply management research from Europe on N. galligena
Nectria and Botryosphaeria cankers Management (sanitation): Prune (summer pruning or dead/disease shoots): cool day following a 24-hr period of dry weather with two days of dry weather forecasted following pruning Infection on leader or trunk of small tree > remove tree and replant
Nectria and Botryosphaeria cankers Management: Remove cuttings from orchards and burn them or take them offsite > they can still infect from the ground Apply copper fungicides: 20% and 80% leaf drop and after pruning (fruit finish) Kocide 3000 & Badge SC Badge x 2 are labeled for Nectria (European canker)
Nectria and Botryosphaeria cankers Management: Use biologicals and fungicides to protect wounds only > can t access the fungi otherwise No resistance to wood decay fungi in pome: species w/high phenolic content can be somewhat slower to decay (e.g. Pinus & Sequoia)
Phytophthora root & scion rot Causal agent(s): Phytophthora spp. Symptoms: (dysfunctional root system) Stunting, reduced terminal growth, chlorotic foliage, small premature colored fruit
Phytophthora root & scion rot Causal agent(s): Phytophthora spp. Symptoms: (dysfunctional root system) Below bark: orange/reddish brown spreading lesions darkly delineated margin = activing infection Secondary wood decay fungi and bacteria colonize & confound diagnosis
Phytophthora root & scion rot Disease cycle: Infection: zoospores release from sporangia in saturated soils in the snows melts in the spring as temperature rises Phytophthora is ubiquitous in soils and usually occurs in low lying or poorly drained spots However, heavy rains, infected nursery stock, highly susceptible cultivars, & infected nursery stock > even show on the top of a hill Survival: Oospores in soil (long-term) sporangia (short-term)
Phytophthora root & scion rot Management: Plant on well drained soils/hill sides Select resistant rootstocks (B.9 & Geneva series) Avoid susceptible scion varieties to avoid collar rot ( Topaz & and Cox s Orange Pippin ) Apply mefenoxam band/broadcast (2qt/A) or soil drench (0.5pt/100 gal 1-3qt/tree: ($800/gal) Phosphorous acid fungicides first flush or foliage, reapply on 60-day interval: ($33/gal) > damage could be done prior to infection
Winter injury Symptom development The last part of the tree to harden off are the lower scaffolds (just above or below the lowest branches) Browning of the phloem (white) & cambium (green/white) under the bark in irregular patches or streaks. Bark may split and peel Courtesy of Dave Rosenberger
Winter injury Symptom development Browning of the phloem (white) & cambium (green/white) under the bark in irregular patches or streaks. Bark may split and peel If cold kills bark, cankers may form over xylem infected by wood decay fungi (e.g. Schizophyllum commune) Courtesy of Dave Rosenberger
Winter injury Cause: cold temperatures or rapid changes in temperature Low lying areas: colder & poorly drained soils keep trees growing & harden off later Southwest injury (trunk > 3 dia.): light warms bark >30 o and cools down at night or 55 o day in winter followed by 25 o day Ice collars: trees settle leaving a depression that allows water to collect in the depression and refreeze during winter temperature changes
Management Winter injury Avoid poorly drained and low-lying areas Irrigation/fertilizer management: too much water or fertilizer > trees growing late into fall Take care with herbicide use > mild damage may decrease cold hardiness Late summer pruning > decrease cold hardiness Rootstock selection: MM.106 slow hardening: Geneva series G.935 good cold tolerance Scion variety: Empire, Fuji, and Rome vs McIntosh and Gala
Acknowledgements Program research funded by: Apple Research and Development Program New York State IPM North American agrichemical industry: Syngenta, BASF, Bayer, Dow, & Dupont
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