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Issue No. 1, Article 5/March 16, 2005

Degree-Day Accumulations Behind Compared to One Year Ago

Average winter temperatures were higher than they were last year and were warmer than normal (Figures 1 and 2). However, we are considerably behind in degree-day accumulations compared to one year ago. How is that possible, you might ask? Temperatures in March thus far have been 2 to 6 de-grees below normal across the state (Figure 3). Degree-day accumulations from January 1 through mid-March (2004 and 2005) are compared in Table 3. Throughout the growing season, you can check on degree-day accumulations on insects and growing degree-days for crops at the Degree-Day Calculator.

The degree-day calculator is an Internet tool developed to assist Illinois producers in making pest management decisions using pest development models and Illinois climate data. A collaborative effort between the Integrated Pest Management program (Department of Crop Sciences, University of Illinois) and the Illinois State Water Survey (Illinois Department of Natural Resources), the degree-day calculator provides users with the ability to determine degree-day accumulations for specific pests of field crops, fruits, and vegetables in Illinois. The calculator tracks and projects the growth of insect pests and crops in Illinois. It is designed to help the user determine when to monitor for specific insect stages that may be approaching in their region and aid in subsequent management decisions. Just as important, it provides this information in an up-to-date format that is designed to be user-friendly.


Figure 3. Average temperature departure from the mean (in degrees F) from March 1 to March 14, 2005. Source: Midwestern Regional Climate Center, Illinois State Water Survey, Champaign.

Currently, degree-day calculations can be generated for 30 different insects at each of 19 weather sites. The degree-day calculator can also generate contour maps for specific insects and base temperatures. If the user wants to compare degree-day accumulations between different locations, the map function affords them this option. Whether determining degree-days at one site or creating a contour map, both of these functions can project degree-day accumulations 1 and 2 weeks into the future. Information is also provided to describe the relationship between insect developmental stages and degree-day accumulations, as well as a background section on how degree-days are calculated. Additional information on the insect's life cycle, potential injury, scouting procedures, and management can be found via a link to an insect fact sheet on the IPM Web site.

During the course of the spring and summer, we will undoubtedly make reference to degree-days and approaching insect stages. We hope that you too take advantage of this tool and use it to stay on top of developing insect problems--Kelly Cook

Kelly Estes

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