Peter B. Goodell UC Cooperative Extension Statewide IPM Program - Kearney Ag Center Lower San Joaquin River Sustainable Farming Program Meeting 12/12/12

Topic Overview What are degree-days? Why are they needed? How are degree days calculated? How can they be used? What are phenology models? Its all about temperature © Regents of University of California Goodell UC IPM 12/12/12

Calendars vs. Developmental Time Organisms that can control their internal temperatures to a constant level (97.6°F for humans), appear to develop according to calendar Organisms that are dependent on the ambient temperature, appear to have development which speeds up or slows down relative to calendar 12/12/12

Arthropods and Plants Are cold-blooded Require external heat to maintain growth and development Cannot regulate internal temperatures as efficiently as mammals or birds Environment determines growth rate Human Pregnancy is 9 months Regardless of location Human Pregnancy is 9 months Regardless of location 12/12/12 © Regents of University of California Goodell UC IPM

Insects Depend on External Temperature The outside temperature determines the rate or speed of development and the number of generations that occcur over time There is a minimum temperature below which they cannot develop, generally 50°- 60°F. 12/12/12 © Regents of University of California Goodell UC IPM

Population Development of a Hypothetical Insect in 3 Locations Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 12/12/12 © Regents of University of California Goodell UC IPM

Population Development of Two Hypothetical Insects at Same Location Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec /12/12 © Regents of University of California Goodell UC IPM

What is a Degree Unit? It is a measure of an arbitrary thermal unit over time The amount of heat which occurs over a period of time, minutes, hours or days Pest managers most often talk about degree-days (°day, or dd) A degree-day is single degree (F°) above some threshold for 24 hours Provides the method to predict an organisms development 12/12/12 © Regents of University of California Goodell UC IPM

Calculating Degree-Days The following are needed to calculate degree days: – Ambient temperature measuring device, e.g. thermometer – Lower threshold, the temperature BELOW which the organism will not develop Sometimes an upper threshold is required, the temperature ABOVE which the organism will not develop 12/12/12 © Regents of University of California Goodell UC IPM

days 66 days 50 days 40 days COLD HOT How Are Developmental Thresholds Determined? 12/12/12 Courtesy of M Johnson

Time Temperature 24 hours Max temp Min Min temp Record the temperature in the environment 12/12/12 © Regents of University of California Goodell UC IPM Courtesy of M Johnson

Time Temperature 24 hours Max temp Min Min temp Lower Threshold DD Calculate the area under the curve 12/12/12 © Regents of University of California Goodell UC IPM Courtesy of M Johnson

Time Temperature 24 hours Max temp Min Min temp Lower Threshold DD Upper Threshold Calculate the area under the curve 12/12/12 © Regents of University of California Goodell UC IPM Courtesy of M Johnson

Time Temperature 24 hours Chilling Threshold Calculate the area under the curve 12/12/12 © Regents of University of California Goodell UC IPM

What is Required to Use Degree Days IPM Programs? 1.Need temperature data – Min-Max thermometer will work – Remote weather station system (hourly) – Dedicated weather station (every minute) 2.Need to method to calculate – DD= daily average- lower threshold – Use an existing program which can access remote data or input your own 3.Need a purpose 12/12/12 © Regents of University of California Goodell UC IPM

What is a Phenology Model? A phenology model is a model of an organisms development The amount of degree days required for an organism to reach a stage Research based, lab or field Examples: – Cotton seeding to emergence (basis of planting forecast) – Cotton seeding to first square, flower or boll – Moth flight to egg hatch 12/12/12 © Regents of University of California Goodell UC IPM

Why Are Phenology Models Used in IPM Programs A good pest management program TARGETS the most susceptible stage BEFORE the population can cause economic damage Phenology models can PREDICT when those stages will present Control actions can be taken at the most appropriate TIMING 12/12/12 © Regents of University of California Goodell UC IPM

Cotton Planting Forecasts Planting cotton seed into the most optimum conditions is the best start for managing pest and production for the rest of the season A vigorous crop can better withstand stress Research demonstrated that Degree-days> 60 for 5 days after planting is the best predictor Fewer than 15 DD60 is Unfavorable to Marginal conditions More than 16 DD60 is Adequate to Ideal 12/12/12 © Regents of University of California Goodell UC IPM

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Phenology or Developmental Events in Cotton Growth Event Short Season Variety Acala Pima 1 st Square st Bloom Peak Bloom st Open Boll % Open Boll Accumulated Degree-days > 60°F since planting 12/12/12 © Regents of University of California Goodell UC IPM

Cotton Development 2012 vs. 30 Yr Average 12/12/12

Additional Examples of Phenological Models Cotton slide rule, ca Alfalfa model, Alfalfa Weevil model Beet armyworm California red scale Codling moth Consperse stink bug Cotton Elm leaf beetle Fire blight risk for apple and pear Fuller rose beetle Grape powdery mildew index Lygus bug Navel orangeworm Obliquebanded leafroller Omnivorous leafroller Orange tortrix Oriental fruit moth Peach twig borer Pink bollworm San Jose scale Tomato fruitworm Tomato powdery mildew spray forecast 12/12/12 © Regents of University of California Goodell UC IPM

Useful Resources UC IPM – ipm.ucdavis.edu Pest and Plant Models Video: How to Use Degree Days dex.html 12/12/12 © Regents of University of California Goodell UC IPM

Thank You For Your Attention 12/12/12Goodell UCCE IPM