No. 1 Article 2/March 18, 2004

Internet Source for Daily Pest Degree-Days and Growing Degree-Days in Illinois

A new and exciting feature on the IPM Web site will provide you the ability to determine degree-day accumulations for selected pests throughout the season. The development of the project was a collaborative effort among scientists with the Illinois State Water Survey and the Department of Crop Sciences at the University of Illinois. In particular, I wish to thank Bob Scott (Illinois State Water Survey) and Kelly Cook (Extension IPM--Entomology, Department of Crop Sciences) for providing leadership for the project. The end result will enable you to combine daily weather data and pest information to generate Web pages showing current degree-day totals in Illinois associated with pest and crop development.

Following is some of the text from a recent press release prepared by Bob Scott: "The agricultural community in Illinois now has a new Internet tool to track growth cycles of agricultural pests and Illinois crops using daily degree-day totals. This collaborative effort between scientists from the Illinois State Water Survey (, a division of the Illinois Department of Natural Resources, and the Integrated Pest Management Program, Department of Crop Sciences ( at the University of Illinois, combines daily weather data and pest information to generate Web pages that show current degree-day totals in Illinois associated with pests and crop development.

"Growth of pests and crops in Illinois can be tracked and projected by maintaining an account of the 'heat' accumulated during each growing season. This process involves comparison of daily maximum and minimum temperatures to a base temperature, specific for a particular pest or crop, above which development of the pest or crop will occur. Computer algorithms were developed for tracking 30 agricultural pests and also determining growing degree-day totals for corn and cold weather crops.

"Degree-day accumulations for some pests, regardless of their location in Illinois, have a specific calendar day when heat tracking begins, such as January 1 each year. Local accumulations for other pests and those for crops are tied to specific, user-provided events: first spring trapping of adult pests, sighting of insect eggs, planting date, etc. One- and two-week degree-day projections, based on climate records at each site, also are included. The tool also produces maps of degree-day totals and projections for the entire state where appropriate.

"This information is computed from data collected at 19 weather sites across Illinois and is specific for those locations. These data are valuable in helping users determine when to monitor their fields for approaching stages of pest development and with the subsequent operational decisions that follow.

"All degree-day information is computed from data collected through the day just prior to the day each user accesses the system. In general, up-to-date information will be available by 4:00 a.m., seven days a week. The URLs are (pests and crops) and (pests)."

If you access the degree-day accumulation tool through the IPM Web site, you first will encounter a page that explains insect growth and development, with specific references to minimum and maximum developmental thresholds. Kelly Cook prepared all of the information associated with this page. Clicking on "Degree-Day Calculator" in the upper right corner takes you to a Water and Atmospheric Resources Monitoring (WARM) Web page that enables you to select the "Degree-Day Calculator" or "Degree-Day Maps." By selecting "Degree-Day Calculator," you will be able to select from a list of pests (e.g., alfalfa weevil), select a site from the map (e.g., Dixon Springs), and calculate the accumulated degree-days through the end of the preceding day. By selecting "Degree-Day Maps," you can choose from a small list of insects and obtain maps that show current totals, one-week projections, and two-week projections for accumulated degree-days for the state of Illinois. Both a map and a table are displayed. The maps are the same as the maps we have been printing in the Bulletin for years.

We hope that this new feature is useful for you. Because of its availability, we no longer will provide printed maps in the Bulletin. However, we will refer to accumulated degree-days in articles written about the insect in question. Let us know what you think, and don't hesitate to contact us if you encounter any problems. Happy accumulating!--Kevin Steffey

Close this window