Degree Day Update and Temperature Comparisons

For those readers living in Illinois, Indiana, Wisconsin, Michigan, or Ohio, there’s a handy degree day information site available, courtesy of Michigan State University, and supported by several turfgrass associations. All you have to do is enter your zipcode  and the site provides you with a chart indicating the degree days to date for your specific location. Since the website is primarily for the benefit of those managing turf, there are also charts to tell you the window for applying pre-emergent crabgrass control, when to be on the lookout for Japanese Beetle grubs, and so forth, as well as a “blog” containing insights on turf, weeds and insects by state university professionals. Growing Degree Days are used to monitor crop growth as well as insect emergence that affect many different plants, so even though this particular site focuses on turfgrass pests, the GDD information is the same that is used for all plants and pests.

Since GDD calculations are based on average temperatures exceeding 50°F. to date during the calendar year, it’s interesting to compare current conditions with both the prior year and the norm. Those of us living in the Midwest are not just imagining a substantially cooler spring than normal. For example, the Growing Degree Days in Milwaukee this year as of May 18, 2011 were 143. That compares with 295 by May 18, 2010, and a norm of 274 by May 18. It’s no wonder that plant growth is so slow this year.

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