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:
- Degree Day Concepts (UC-Davis)
- Weather and Modeling (UC-Davis) (has videos on how to use DD).
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 (More info) | 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 (More info) | Modified | 50F | 86F | Emergence |
| Corn Rootworm Adults | Simple | 50F | None | January 1 |
| Cranberry plant development | Modified | 45F | 86F | Ice off |
| European Corn Borer (More info) (Sweet corn, Field corn) |
Modified | 50F | 86F | January 1 |
| Seedcorn Maggot (More info) | Sine | 39F | 84F | January 1 |
| Flea beetles (Beet, Cole crops, Potato) |
Simple | 50F | None | January 1 |
| Imported Cabbageworm | Simple | 50F | None | January 1 |
| Onion Maggot | Simple | 40F | None | January 1 |
| Oak Wilt | Sine | 41F | None | January 1 |
| Squash Vine Borer | Simple | 50F | None | January 1 |
| Stalk Borer (More info) (Sweet Corn, Field Corn, Potato, Snap Bean) |
Sine | 41F | 86F | January 1 |
| Tree and shrub pests | Modified | 50F | 86F | January 1 |
| Western Bean Cutworm (More info) | Simple | 50F | None | May 1 |