Using Degree-Day Tools To Improve Pest Management: Dont get caught off-guard!

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Using Degree-Day Tools To Improve Pest Management: Dont get caught off-guard !

Len Coop, IPPC, OSU Corvallis Jan 25, 2012

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Degree-day/phenology concepts

Some features of the IPPC "Online weather data and degree-days" website at uspest.org/wea

Development and use of specific models – example applications

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"Who?" and "What?"

Identification keys, diagnostic guides, management guides

"When?"

Phenology models (crops, insects, weeds), Risk models (plant diseases)

"If?"

Economic thresholds, crop loss models, sampling calculators, other decision tools

"Where?"

GIS, precision agriculture

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"Who?" and "What?"

"When?"

"If?"

"Where?"

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"Who?" and "What?"

"When?"

"If?"

"Where?"

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"If?"

Economic thresholds: do numbers of pests justify treatment?

"Where?"

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What to know about degree-days:

Insects have complex life cycles

Eggs Larvae

Pupae (most) Adults

-Timing of all stages is

*typically*

predictable using

degree-days, which are a two dimensional “heat unit“ of development for cold blooded

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Heat unit concepts and examples first published by Reaumur (1736), modern refs. in Arnold (1959, 1960)

Degree-day models in common use for timing of sampling and management events in agriculture; a cornerstone of IPM

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Phenology: the study of periodic phenomena in their relations to each other, as climatic and weather changes to plant life (from Torre-Bueno 1st ed.)

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Degree-day calculations – method varies:

Simplest: (daily max + min)/2 – low threshold

Single triangle compared with typical daily fluctuation

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Different organisms have different lower thresholds for development. Examples include:

Plants: ca. 30 to 45 F – Wheat: 32 – Corn: 50 Insects: ca. 38 to 55 F – Aphid: 38 – Leafrollers: 41-44

– Codling moth, spotted wing Drosophila: 50

– Lygus bug, stink bug: 52-54

– Bees: can generate their own heat in the hive (with limits)

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 Simple average: daily max + min/2 - lower threshold (ignores any upper threshold)

 Growing degree-days for corn: use simple avg but subst lower threshold in place of min (if min is lower), subst upper threshold in place of max (if max is higher)

 Growing degree-days for cereals: same as simple average  Single and double triangle: simple geometric formulae (the

latter uses tonights min for second half of today)

 Single and double sine curve: more complex trig. formulae  Actual degree-days: computed in real time ex. once/minute  Degree-hours: require hourly data

 Fireblight degree-days: 4-day running degree-day total

 Heating and Cooling degree-days: used by the power industry

Types of degree-days

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Assume that developmental rate is linearly related to temperature above a lower threshold (Tlow)

Work best in temperate regions for populations that have relatively few, non-overlapping generations

DD models often require a "biofix" - biological monitoring event used to initialize the model

(biofix = starting date that the user inputs)

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35 40 45 50 55 60 65 70 75 80 85 90 95 0 25 50 75 100 125 150 175 200

Temperature vs. development time

Development time (days) Temperature (F) D a ys

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 35 40 45 50 55 60 65 70 75 80 85 90 95 0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.055 0.06

Temperature versus development

Development time (days) Rate (1/days) Temperature (F) R at e (1/ da y s )

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 35 40 45 50 55 60 65 70 75 80 85 90 95 0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.055 0.06

Temperature versus development

Development time (days) Rate (1/days) Temperature (F) R at e (1/ da y s )

Degree-day models: x-intercept method (Arnold 1959)

x-intercept ~ Tlow = 37 F

1/slope = 1/0.0011 = 920

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Weather and Degree-day Concepts

1)Degree-day models: accumulate a daily "heat unit index" (DD total) until some event is expected (e. g. egg hatch)

38 20 18 32 14 22 20 26 daily: cumulative: ₂₀ 70 84 106 126 152

Eggs hatch: 152 cumulative DDs Eggs start developing: 0 DDs

70o(avg)

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Weather and Pest/Disease Models

Over 73 DD/phenology models available Over 18 Disease risk/hourly driven models

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Example multi-regional Disease Alert Map integrating real-time

observed and forecast weather data into one disease index:

Forecast fire blight risk model available at the IPPC website http://uspest.org/wea

Other Disease Alert Maps include: Tomato-potato late blight, Tomcast DSV, Soybean rust, also animated

movies are available for each of these.

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Prism Interpolated Degree-Days

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What is Climate Mapping?

The process of interpolating climate statistics at irregularly-spaced station locations to a regular grid

“Geospatial Climatology”

The study of the spatial patterns of climate on the earth’s surface and their causes

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Summary Points:

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Degree-day/phenology models can help in timing of

sampling and treatment based on weather trends

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IPPC uspest.org/wea has evolved as a hybrid for

support of State, Regional, and National needs

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“MyPest Home Page” now integrates numerous models

and weather in one place

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Degree-day maps can help show how timing varies over

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Degree-days: a tool for decision support, not

another tool we can store in the tool shed

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Using Degree-Day Tools To Improve Pest Management: Questions?

Len Coop, IPPC, OSU Corvallis Jan 25, 2012