The concept of ‘normal’ temperatures might be a thing of the past. After record warm temperatures last year, and record cold temperatures this year, tracking degree days is more crucial than ever. A degree day (DD) at its simplest is an average of the daily high and low temperature minus a developmental threshold. As DDs accumulate over the course of a summer, they can be used to predict certain events like bloom, moth flights, etc., regardless of the calendar date. Currently only the thresholds for the cranberry plant are published (lower threshold: 41°F, upper threshold: 85°F). These thresholds are used for predicting the stage of plant growth but only provide a rough estimate for insect development. We are working on determining the specific thresholds for Sparganothis fruitworm and we should have these results ready by the end of the summer (stay tuned!).
So how delayed are we? The DD accumulations calculated from March 1-May 15 for the past 6 years for Tomah, WI (41/85°F thresholds, single sine method, horizontal cutoff) are:
2008 – 369
2009 – 463
2010 – 607
2011 – 354
2012 – 832 (wow!)
2013 – 336
It seems that slowly, but surely, spring is arriving.
If you are interested in calculating your own DD accumulations, the University of California-IPM has an excellent DD calculator available on their website. Scroll down to the bottom of the page, enter your upper and lower thresholds (the default calculation methods are fine for the rough estimate) and click on calculate. You can then either enter your weather data online or upload a file.
Cranberries were featured in the latest article about the challenges that agricultural producers face in a changing climate. Rebecca Harbut and Ed Grygleski were interviewed about the unusual weather patterns that stressed the vines this past growing season. See pages 3 and 4 of the article for their contribution.
The College of Agricultural and Life Sciences, at University of Wisconsin-Madison, publishes Grow Magazine three times a year, highlighting agricultural research in Wisconsin. The University offers a free subscription, go here for the subscription form. For a pdf copy of the latest Grow issue, Spring 2013, go here.
— Liz Bosak
Cranberry, a fruit native to North America, is grown primarily in Wisconsin, Massachusetts, New Jersey, Maine, Oregon, British Columbia, Quebec, and Washington. Contrary to the public’s perception from television commercials, cranberries are not grown underwater. Flooding is used periodically throughout the growing season for harvest, pest control, and frost protection. Cranberry marshes are intimately tied to their wetland areas to provide water for irrigation, frost protection, and flooding.
Wisconsin cranberry growers have avoided many negative effects of the drought but the same is not true for growers in Washington. Reduced water resources may delay or prolong the harvest. For the full Seattle Times article, go here.
Click here for the latest article from the Wisconsin State farmer discussing this year’s early Spring and cool temperatures. A Michigan State University extension article covers growing degree day accumulations for this Spring and its impacts on grape production. If you’d like all of the gory details of how frost injures plant tissue, then check out Janna Beckerman’s article at Purdue University.
The National Agricultural Statistics Service offers weekly email updates for a variety of crop data including crop-weather data, for more information go here and for Wisconsin click here.
Still want more information, check out this earlier post.
Recently, Shawn posted an article on the Entomology Department’s website about frost injury to cranberries in Wisconsin, follow this link.
For more information about spring frost injury in Wisconsin fruit crops, go to the University of Wisconsin Extension Fruit Crops website.
Specifically, see Rebecca Harbut’s article on “Understanding Frost in Fruit Crops”. She and Patty McManus have another article on “Impacts of High Spring Temperatures on Fruit Crop Management”.