UW Extension Ag Weather

Contour map

Thermal Models

Pic 2

Degree Day Calculator

Degree days totalize the amount of heat available above a threshold temperature since a given day. The number of degree days accumulated over some period of time is often related to the phenological development of plants and insects, and so can be used to estimate when pests will be at a life stage vulnerable to control. The base, or lower threshold temperature is that below which the organism does not grow or develop. The cap, or upper threshold is the maximum temperature at which organismal development occurs. Some specific examples can be found at our European Corn Borer and Alfalfa weevil web pages.

For more information, see:

Note: These parameters are usually specific for a particular crop and pest. Make sure you are using the right ones for your particular situation. Some values for common pests in our area are listed below.

Pest Method Base Temp Upper Temp Biofix
Apple Scab Simple 32F None Bud break
Alfalfa Weevil (DD Map) Sine 48F 86F January 1
Black Cutworm Sine 50.7F 86.0F
Cabbage Maggot Simple 43F None January 1
Colorado Potato Beetle Simple 52F None When eggs are first scouted
Common Asparagus Beetle Simple 50F None January 1
Corn plant development (DD Map) Modified 50F 86F Emergence
Corn Rootworm Adults Simple 50F None January 1
Cranberry plant development DD Map Modified 45F 86F Ice off
European Corn Borer (DD Map)
(Sweet corn, Field corn)
Modified 50F 86F January 1
Seedcorn Maggot (DD Map)
Sine 39F 84F January 1
Fleabeetles
(Beet, Cole crops, Potato)
Simple 50F None January 1
Imported Cabbageworm Simple 50F None January 1
Onion Maggot Simple 40F None January 1
Squash Vine Borer Simple 50F None January 1
Stalk Borer (DD Map)
(Sweet Corn, Field Corn, Potato, Snap Bean)
Sine 41F 86F January 1
Tree and shrub pests (DD Map) Modified 50F 86F January 1
Western Bean Cutworm (More information) Simple 50F May 1

Simple
Modified
Sine
Biofix (start) date
End date
Lower threshold temperature (Degrees F):
Upper threshold (F)
Report only last 7 days of accumulated values
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