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

Fly Speck / Sooty Blotch

Black rot (Botryosphaeria)

Bitter rot (Colletotrichum)

Pinpoint apple scab

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- 2nd cover or 14-21 days from 3rd-7th 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 2nd 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 1st & 2nd 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

2014 Trial: TopazUntreated Cueva & Double Nickel

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. infecttrees 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. Schizophyllumcommune)

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

>30o and cools down at night or 55o day in winter followed by 25o day

– Ice collars: trees settle leaving a depression that allows water to collect in the depression and refreeze during winter temperature changes

Winter injury

• Management– 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

Questions