weather stations and disease warning systems for apple and grape

Weather Stations and Weather Stations and Disease Warning Systems for Disease Warning Systems for

Apple and GrapeApple and Grape

What are they and what can they do for you?

Patty McManus and Steve Jordan

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What are we talking about?What are we talking about?

• Disease warning system

• Disease risk advisory system

• Disease forecasting system

• Disease prediction system

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What are we talking about?What are we talking about?

Disease model– Mathematical formula that you plug

environmental data into– Can be very simple (e.g., degree days) or more

complex requiring a computerModels use quantitative data (e.g., amount of rain,

temperature, % RH, number of hours of leaf wetness)Disease warning systems usually include qualitative

information (e.g., cultivar, growth stage, disease history)

Disease Warning SystemsDisease Warning Systems

Based on sound science, validated in real orchards, but not foolproof

Environmental conditions vary across an orchard or vineyard and even within a canopyIndividuals in a fungal population vary in their optimal temperature/wetness requirements for germination and growthDifferent cultivars differ in susceptibility

IPM tool to be used with other IPM tools

Main ObjectiveMain Objective

Improve your understanding of environmental monitoring equipment and disease warning systems so that you can use the technology to your best advantage.

Collecting Environmental DataCollecting Environmental Data

• On-site instruments (e.g., Spectrum, Hobo, Metos, Campbell); most require computer software to run models.

• Remotely sensed data (e.g., Skybit), advisory e-mailed or faxed daily.

Purchasing a Weather StationPurchasing a Weather Station

• Number of makes and models available

• Spectrum, Hobo, Metos, Campbell

• What suits your needs and budget (and disease models)

• temperature sensor• Relative humidity

sensor• Typically housed

within a radiation shield

Necessary ComponentsNecessary Components


• Leaf Wetness Sensor– Measures the duration of

water on the surface of “leaves”

– Northern exposure is optimum (last to dry out)

– Necessary for most models

• Rain Gauge– Number of different

types

– Tipping bucket most common


Other Useful ComponentsOther Useful Components

• Anemometer – used for measuring

wind speed– Avoid spray drift

• Weather vane– Wind direction

Powering your Weather StationPowering your Weather Station• Number of options depending on your weather station

– Small batteries (AA, 9 Volt, etc..)• Cheap, reliable?

– Marine battery• Relatively affordable, but must charge or change out

batteries periodically– Solar panel

• Self-sustaining, can be unreliable depending on weather and energy needs of the weather station

– Direct line from a power grid • Ideal, but requires close proximity to a power source and

wiring compatiblity to the weather station

Communicating with your Communicating with your Weather StationWeather Station

• “Read-out” display on station– Simplest way– Can limit the amount of information available– Requires interacting directly with the station

• Data shuttle or laptop computer– Download data to a small data shuttle or laptop– Requires interacting directly with the station

• Permanent cable link to a computer– Buried computer cable from you desktop to the weather station– Great if vineyard is next to your house

Communicating with your Weather Communicating with your Weather StationStation

• line-modem link– Weather station is linked to a phone line– Uses a modem to download and send data to your computer– mains power supply and telephone point necessary

• Cellular modem link– Uses a cellular modem (think cell phone) to send data to your

computer– Does not require a main power supply or telephone point, so

good for a remote station– Requires good cellular reception– Can be expensive

• Major diseases, especially eastern North America

• Warning systems commercially available

Apple scab Fire blight Sooty blotch-flyspeck

For scab and fire blight:For scab and fire blight:• Biology as it relates to warning systems

• Origin and development of the systems

• How to make them work for you

• Take-home message

Fall

Secondary infections

Scab BiologyScab Biology

Spring

Ascospores

Degree-day model estimates % of ascospores mature Primary

infections

LWD and temp to identify infection periods

Origin and Development ofOrigin and Development ofScab Warning SystemsScab Warning Systems

• Degree-day model for estimating percentage of ascospores mature

• Leaf wetness- and temperature- based model for identifying infection periods (Mills)

Scab Infection Period ModelsScab Infection Period Models

• Mills as modified by Jones– Temperature and leaf wetness duration

(LWD) hours– Established “Light,” “Medium,” and “Heavy”

infection periods• Washington State model requires more LWD

hours at temps below 47 oF• Cornell model requires the fewest LWD hours

at all temperatures and does away with L,M, and H infection periods

• LWD hours required for infection are approximate, not absolute

• Scab fungus exists as a population of individuals with a range of germination/infection requirements

• Models often developed and validated under “worst-case” scenario:

Highly susceptible cultivar“Abundant” inoculum

Often overlooked points:

Making the scab infectionMaking the scab infectionmodel work for youmodel work for you

• What it will do:– Identify when conditions have been favorable for

infection (assumes presence of spores and susceptible cultivar)

• What it won’t do:– Predict the amount of scab that develops– Predict when scab will appear

• Amount of scab that develops depends on amount of inoculum, cultivar susceptibility, and tissue age

• Rely primarily on preventing infection with protectant fungicides

• When spraying post-infection, use appropriate fungicides– Don’t count on 4 days “kick-back” from sterol

inhibitor or strobilurin fungicides

Making the scab infectionMaking the scab infectionmodel work for youmodel work for you

Making the scab infectionMaking the scab infectionmodels work for youmodels work for you

Scab warning systems are IPM tools that work best if integrated with inoculum reduction and host resistance

Keeping records of weather and infection periods helps you sort out what went wrong when, so that you can do better in the future

Take-home MessageTake-home Message

• Scab warning systems are IPM tools that work best if integrated with inoculum reduction, host resistance, and a preventative spray schedule.

Blossom blight

Canker blight

Erwinia amylovora: doubles every 30 minutes on stigma

Internal movementof bacteria...

…causes shoot infections

Bacteria spread by rain,wind, possibly insectsto new shoots…

…shoot blight

Rootstock BlightRootstock Blight

Most deadly form of fire blight

Not accounted for by fire blight warning systems

Special challenges withSpecial challenges withfire blightfire blight

• Disease development is explosive:– Pathogen grows exponentially– Can infect with just minutes of wetness

• Pathogen can persist asymptomatically, or in hard-to-find cankers, from year to year in apple trees

• Internal and systemic nature of the pathogen limits the effectiveness of chemicals and pruning

• Streptomycin is the only consistently effective bactericide

• Sporadic disease, so we tend to forget stuff and repeat mistakes!

Special challenges withSpecial challenges withfire blightfire blight

Origin and Development ofOrigin and Development ofFire Blight Warning SystemsFire Blight Warning Systems

• Two most used systems in North America:

– Maryblyt: P. Steiner, Univ. Maryland

– Cougarblight: T. Smith, Wash. State Univ.

Maryblyt and CougarblightMaryblyt and Cougarblight

• Both require:• Open blossoms• Accumulation of degree

hours (DH) sufficient for E. amylovora to multiply on the stigma

• Rain or dew to wash the pathogen into nectarthodes

Maryblyt and CougarblightMaryblyt and Cougarblight

• Key differences:• Maryblyt assumes presence

of pathogen; Cougarblight incorporates fire blight history into the risk assessment

• Maryblyt predicts the onset of symptoms; Cougarblight provides low, marginal, high, or extreme infection risk warning

Which should you use?Which should you use?

• E. amylovora is VERY sensitive to environment

• Disease warning systems tend to perform best in the region(s) in which they were developed and validated

MaryblytMaryblyt• Predicts infection and onset of symptoms:

– Canker blight– Blossom blight– Shoot blight– Trauma blight

Canker BlightCanker Blight

Starting at green tip,196 DD (base 55F)

1. 198 DH (base 65F) within the last 80 DD (base 40F)

2. Heavy dew or 0.01 inch rain during current day or 0.1 inch rain previous day

3. Current daily average temp 60F or more

Blossom BlightBlossom Blight

INFECTION

103 DD (base 55F)

Epiphytic Inoculum Potential (EIP)Epiphytic Inoculum Potential (EIP)

• E. amylovora population is building up on stigma, and EIP approaches 100

• EIP = 100 is the infection threshold

• EIP = 100 reached after 198 DH (base 65F) within the last 80 DD (base 40F)

EIP is dynamicEIP is dynamic

Maryblyt assumes cold weather or streptomycin will reduce E. amylovora to marginal levelsA 3-day cool period reduces EIP to 0, unless EIP had previously exceeded 200After streptomycin application, EIP is reset to zero

Shoot BlightShoot BlightTrauma BlightTrauma Blight

103 DD (base 55F) anddaily average temp 60F or more

Wind, rainsplash, insects (?)

White apple leafhopper—NO

Potato leafhopper—MAYBE Green apple aphid—NO

Do insects spread E. amylovora and/or facilitate infection?

Making fire blight warningMaking fire blight warningsystems work for yousystems work for you• What they will do:

– Indicate when blossom infection is likely– Guide timing of streptomycin application during

bloom (best if applied before infection)– Predict the onset of symptoms to guide scouting

early removal of diseased tissues

• What they won’t do:– Predict rootstock blight– Save a lot of sprays in any one year– Substitute for common sense

Take-home MessagesTake-home Messages

• Sporadic, explosive, systemic nature of fire blight makes it impossible to control in some years despite timely sprays and removal of diseased tissues

• Cost savings of using warning systems will be realized over several years

Grape Disease ModelsGrape Disease Models

• 5 Models currently available– Powdery mildew – Phomopsis cane and leaf spot– Botrytis– Downy mildew – Black rot

Powdery MildewPowdery Mildew

• Requires air temperature and leaf wetness• Predicts two infectious stages, an ascospore stage and a

conidial stage– Ascospores are released in the spring from overwintering

structures (primary infections)– Ascospore infection period described as “Heavy”– Condia are released from lesions through the growing season

(secondary infections)– Conidial Index:0 - 30 = Light infection risk40 - 50 = Medium infection risk60 - 100 = Heavy infection risk


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May 01 May 29 J un 26 J ul 24

Ascospore

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Conidial

Vernon W S 2010 - P owdery Mildew - Grape

Ascospore S everityConidial Index

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Ascospore

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Conidial

Vernon W S 2010 - P owdery Mildew - Grape

Ascospore S everityConidial Index

Phomopsis Cane and Leaf SpotPhomopsis Cane and Leaf Spot

• Requires air temperature,leaf wetness, and rain data • Developed using two different varieties, Catawba and

Seyval– Risk calculated as expected number of lesions per leaf– 1 – 30 = light infection risk

31 – 90 = medium infection risk90 + = heavy infection risk


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Vernon W S 2010 - P homopsis Cane+Leaf S pot - Grape

W et H oursCatawba IntensityS eyval Intensity

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Vernon W S 2010 - P homopsis Cane+Leaf S pot - Grape

W et HoursCatawba IntensityS eyval Intensity

BotrytisBotrytis

• Model requires air temperature and leaf wetness data

• Three levels of infection risk; light, moderate and high

• U.C. Davis recommends spraying when risk is above 0.5

BotrytisBotrytis

BotrytisBotrytis

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Vernon W S 2010 - Botrytis - Grape

W et HoursHours R H >95R isk Factor

Vernon W S 2010 - Botrytis - Grape

W et HoursHours R H>95R isk Factor

Downy MildewDowny Mildew

• Model requires leaf wetness, relative humidity, and temperature data

• The model estimates three levels of infection likelihood• Level 1, or “Possible Infection”, infection can occur but

conditions are not optimal• Level 2, or “Medium Risk of Infection”, possible light infection,

low risk• Level 3, or “High Risk of Infection”, conditions are optimal for

infection


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Hours

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Grant W S 2010 - Downy Mildew - Grape

W et Hours95%R H 43-8695%R H 66-77R isk

Grant W S 2010 - Downy Mildew - Grape

W et Hours95%R H 43-8695%R H 66-77R isk

Black RotBlack Rot

• model uses temperature and leaf wetness period to estimate the onset of an infection period

• The model uses a risk rating system to determine the likelihood of infection• Value of 1 = shortest possible period for successful infection• As values go up, the “window” for infection increases

Black RotBlack Rot

Black RotBlack Rot

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Grant W S 2010 - B lack R ot - Grape

W et HoursDaily R isk



Black Rot ScenarioBlack Rot Scenario

• You have had black rot troubles in previous years, but are “on top of it” this year

• Last application of fungicide (Mancozeb and Rally) on June 1st

• Its now the 10th, and its rained several times in the last week with lots of dew and relatively warm temperatures at night. No rain is forecasted until the 15th

• Do you spray now, wait until your next “scheduled” spray date (the 14th) and what product(s) do you apply?

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TMP RNF WET

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W et H oursDaily R isk

• Last application of fungicide (mancozeb and rally) on June 1st

• Its now the 10th, and its rained several times in the last week with lots of dew and relatively warm temperatures at night. Rain is forecasted for the 15th with warm days and nights expected

• Do you spray now, wait until your next “scheduled” spray date (the 14th) and what product(s) do you apply?



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Questions?

weather stations and disease warning systems for apple and grape

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