PREDICTING DISEASE INFECTION PERIODS: TOOLS, TRICKS, AND UPDATES

Kari Peter, Ph.D.Department of Plant Pathology and Environmental MicrobiologyPenn State University Fruit Research and Extension CenterBiglerville, PA kap22@psu.edu 717-677-6116 Ext 223 @drtreefruit

Apple scabFire blightSooty blotch and Flyspeck

Bacterial spot

Disease cycle Infection conditionsTools to help predict

infectionManagement

Predicting disease infection periods: tools, tricks, and updates

APPLE SCAB

Disease cycle of Venturia inaequalis:

Spores overwinter

Spring: primary inoculum

Secondary inoculum

polycyclic

APPLE SCAB

Ascospores: • Mature at GT• Temperature• Discharged by

early spring rains

• **Peaks: Bloom - PF

• Primary infection can last until mid-June

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Phenology of apple trees

Primary Period for Dispersal of Apple Scab Ascopores

Disease conditions present = control is critical

Temperature (°F)3436373941434546485052

54 – 5657 – 59 61 – 75

7779

Wetness hours4135302821181513121198768

11

Lesion appearance (days)

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17171717161514

12 - 13 9 - 10

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Predicting apple scab infection: Mills Table

Severe: rainy springLittle: hot and dry

Manually estimating:• Average

temperature (max and min temperatures during wetting event

• Calculate leaf wetness hours: When wetting event starts and then when leaves dry

Utilizing NEWAto predict infection periods

www.newa.cornell.edu

Stations in PA:Piney Mountain, PABiglerville (Hollabaugh), PAYork Springs (Lerew), PANew Paris (Boyer), PANew Tripoli (NWLHS), PAScott Township, PARock Springs, PANorth East Escarpment, PAHarborcreek, PA

13 Airports available

In Maryland:Woodbine, MD (Howard -Carroll Counties)

Utilizing NEWA:

Select a disease:Fire blightApple ScabSooty blotch and Flyspeck

Weather station

Date of Interest

Utilizing NEWA: Apple scab infection periods

It’s April 29:Scab infection period predicted for April 30 –May 1 Protection needed BEFORE infection invent

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Phenology of apple trees

Primary Period for Dispersal of Apple Scab Ascopores

Disease conditions present = control is critical

Scab infection period presents itself, keep in mind where we are during the ascospore dispersal

Management – ½” Green Tip to 1st Cover

• 1/2” Green Tip and Tight Cluster: Syllit + mancozeb (3 lb/A)

• Pink and Bloom: Fontelis + mancozeb

• Petal Fall and 1st cover: Vangard + mancozeb

• Other products can be substituted:Examples: Flint + mancozeb

Inspire Super + mancozebLuna Tranquility + mancozebIndar + mancozeb*Aprovia (2016: new SDHI) + mancozebMerivon/Luna Sensation + mancozeb

• Adding several pounds of sulfur = For powdery mildew suppression

• Rusts controlled with EBDCs (mancozeb/manzate/penncozeb etc.)

Primary infection can last until mid-June

*Protectant:Omega

Rule of thumb: Use contact fungicides in combination with at least 3 different chemistries/modes of action (SPRAY BY THE NUMBERS)

Management – Additional considerations

Be sure your sprayers are calibrated to ensure good coverage!

In very wet weather: ABSOLUTELY MUST RE-APPLY FUNGICIDES IN THE RAIN

• Mancozeb, captan, and sulfur will all provide several days of protection if applied in the rain

• Assume all fungicide protection, regardless of product, will be removed after 2 inches of rain• If extended warm rains occur over the next few days:

AN ABSOLUTE MUST to get out and renew coverage by spraying a protectant (mancozeb, captan, or sulfur) in the rain

• Duration of product: Avoid spraying in pouring rain = product washes off

• Duration of product: Applied during a drizzle = Uncertain about duration, but could expect 2 – 3 days

Management – Additional considerations

Be sure your sprayers are calibrated to ensure good coverage!

• Biggest problem: Poor coverageRight equipment Set up properly

• Ideal: Able to cover acreage in 3 days (or less) if needed to recover during a 2 week wetting period in a wet scab year

Alternate Row Middle sprays…good for wet years

PRIORITIZE COVERAGEMOST SCAB SUSCEPTIBLE CULTIVARS

Getting back through blocks quickly if rain removes all protection and continued wetting is predicted

FIRE BLIGHT

www.apsnet.org

Activecanker

Oozing bacteria: Attracts insects – insects dispersebacteria to flowers (wind and rain also disperse bacteria)

Bacteria colonizestigmas (favors warm temps): does not cause disease (yet)

Fire Blight Disease Cycle

Wetting event + warm temps

Blossom Blight

Shoot BlightCanker BlightTrauma Blight

Rootstock Blight

5 – 30 days

Bloom time

Predicting Fire Blight Infection Periods: NEWANEWA: Predicts fire blight infection periods using Cougarblight

Requirements for infection:• Orchard fire blight history• Starts at first bloom• 4 day accumulation of

degree hours (today + yesterday + 2 days ago + 3 days ago)

• Wetting event (dew, rain, spray treatment)

**Can be calculated by hand using available tables

It’s May 4 and a fire blight infection period is occurring: Spray now

Management – Bloom – Petal Fall

http://www.omafra.gov.on.ca

Blossom sprays protect only flowers that are open (Protect blooms during 20% - Full Bloom)

Antibiotics – complete, + adjuvant or surfactant*Most effective when they are applied the day before or the day after an infection event (within 24 hrs!)

• Streptomycin – Still the best option• Partial systemic activity

• Kasugamycin – Kills bacteria, but not systemic• Oxytetracycline – Suppresses bacteria• 4 spray maximum (resistance management)

*Be mindful of rattail bloom

Management – Bloom – Petal Fall

http://www.omafra.gov.on.ca

Tank mixing with strep: To help manage shoot blight New for 2016: Actigard (Syngenta)• Induces plant resistant• Use mixed with strep (NOT alone)

Regalia @ 64 oz/A

Plant growth regulator: Prohexadione-calcium (Apogee, Kudos) @ 2 – 6 oz/A + organosilicone adj. + ammonium sulfate• Begin king bloom thru petal fall (several apps thereafter)• Hardens off shoots = not susceptible to shoot blight

• Occurs 10 - 14 days after application• Can be tank mixed with strep (NOT a strep replacement)

Do not tank mix copper with strep

Alternatives to antibiotics• Blossom Protect – Yeast antagonist

• Restrictions of what fungicides/insecticides can be used when using product

• Ceuva + Double Nickel• Serenade Opti• 2% Lime Sulfur + 2% Fish Oil• Phosphonate (phosphorous acid) products are not

effective (Rampart, Phostrol, ProPhyt, etc.)

Management – Bloom – Petal Fall

http://www.omafra.gov.on.ca

Management – Post Bloom to terminal bud set

Plant growth regulator: Prohexadione-calcium (Apogee, Kudos) @ 2 oz/A + organosilicone adj. + ammonium sulfate

VIGILANCE: Monitor regularly for infections if there were blossom blight conditions – prune as necessary

• Symptoms manifest 5 – 30 days post infection• Shoot blight infection: risk continues until shoot growth

ceases• Beware of pruning too much – makes fire blight worse

DO NOT spray antibiotics post petal fall• Hail/Severe wind event – the exception

• Cultivar susceptibility, fire blight history, PHI, spray within 24 hrs, crop value justifies cost

Control piercing-sucking insects***

K. Peter

SUMMER DISEASES

Bitter Rot

Sooty blotch and Flyspeck

Predicting Sooty blotch and flyspeck infection:Accumulation of leaf wetness hours beginning 10 days after petal fall

Risk threshold varies depending on what model you use:• PSU: 225 hours• SkyBit: 350 hours• NEWA: 170 hours

It’s June 10 and threshold will be met for risk June 11: Spray now

Predicting SBFS Threshold for control: NEWA

Managing summer diseases

• Weather conditions: Warm (70°F and higher) and wet (rain events)

• Be mindful of fruitlets that don’t completely abscise from fruit thinning Source for fruit rot fungal spores (2015 was bad year for this in PA/MD)

• Remove fire blight cankers : dead/cankered wood a source for fruit rot spores Another reason why it is important to prune out dead/cankered wood

during dormancy

• Previous season fruit mummies (due to apples left on the tree to rot): spore source

• Sooty blotch and flyspeck (~ 2nd cover – NEWA also predicts SBFS infection start): Topsin M + Captan

Oso (Polyoxin D salt; Certis)Omega (fluazinam; FRAC Group 29 Fungicide; Syngenta)

• Fruit rots: QoI fungicides (FRAC Group 11)-- Merivon (0 d PHI); Luna Sensation

and Flint (14 d PHI) [tank mix with Captan] Serenade Opti @ 16 oz/A

BACTERIAL SPOT

Bacterial Spot Disease Cycle

Spring

SummerFall/Winter

Polycyclic diseaseOptimum conditions:Warm and wetDisease slows down:Hot and dry

Overwinter in cankers, infected buds, leaf scars

First infect leaves

Infect leaves and fruit

Left untreated: bacterial

populations “explode”

Bacterial Spot Management

A plan…– Start applications late petal fall to early shuck split

– Spray 7 – 14 days according to conditions

– Rotating other products with oxytetracycline (21 day PHI) and copper (PHI varies)

• Serenade Optimum (14 oz/A) or Double Nickel (1 qt/A)

– Works well in rotation

– Can be tank mixed with oxytet

– For apricots, plums, etc: Cueva, Badge, Kocide, etc; Serenade Optimum, Double Nickel

– ** Always double check the label**

– Phosphorous acid products ineffective

Take home messages:

• Warm and wet favor many diseases

• Monitor orchard conditions and infection events (NEWA)

• Apply control before infection event

• Apple scab: May need to spray during the rain

• Fire blight: tank mix another product with strep to minimize shoot blight (Apogee, Regalia, Actigard)

• Sooty blotch/Flyspeck and fruit rots: Sanitation is important

• Bacterial spot: infection conditions may prompt weekly sprays

2016 – 2017 Penn State Tree Fruit Production Guide

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PREDICTING DISEASE INFECTION PERIODS: TOOLS, TRICKS, AND UPDATES

Kari Peter, Ph.D.Department of Plant Pathology and Environmental MicrobiologyPenn State University Fruit Research and Extension CenterBiglerville, PA kap22@psu.edu 717-677-6116 Ext 223 @drtreefruit

QUESTIONS?