Update 11 – June 20, 2020

Yi Wang, Assistant Professor & Extension Potato and Vegetable Production Specialist, UW- Madison, Dept. of Horticulture, 608-265-4781, Email: wang52@wisc.edu.

This week I have three vlogs to share with you: poor emergence issue in some potato varieties (https://youtu.be/l6GiosGoLts), potato chip processing out of storage (https://youtu.be/16RMafn0Szo), and dark red kidney bean planting (https://youtu.be/YSt9hoOIyrc). I welcome you to subscribe to my YouTube channel “Proud to be a spudbadger!” to stay informed of the latest potato and vegetable production research updates.

For our healthy potato plants that emerged on time (planted between April 30 and May 4), there is about 40% canopy cover as of June 18. Silverton started to flower, and we saw tuber initiation on varieties such as Russet Burbank and Dark Red Norland (picture below). Overall weather looks dry and growers need to keep running their irrigation systems to keep the soil moist during this critical growing stage.

Over the last 12 months, I worked with Dr. Deana Knuteson, director of the Healthy Grown program, and several water specialists at UW-Madison and other state and local agencies to develop an online extension course named the “Water Stewards Training Program”.

This course is built on the CANVAS platform within the UW-Madison website, and is for self-guided- education. The six modules of the course focus mainly on water quantity issues in Wisconsin. They are:

  • Module 1: Basic terms and principals of water conservation in agriculture
  • Module 2: Water management in Wisconsin, overall water levels, natural landscapes and agricultural use, on-farm management of landscapes
  • Module 3: New approaches to optimize water use Module 4: Managing Irrigation to optimize water use Module 5: Modeling water use: approaches and practices Module 6: Implementing water conservation

Water quality is also discussed in many of the modules since it is closely linked with the quantity issue. Six Certified Crop Advisor credits (4 for soil and water, 2 for sustainability) are available for participants upon completion of the course. To sign up for the course, please contact the course moderator, Deana Knuteson (dknuteson@wisc.edu, 608-347-8236) who will add you to the system and let you start the process.


Amanda Gevens, Dept. Chair, Associate Professor & Extension Specialist, UW-Madison Plant Pathology, gevens@wisc.edu, Cell: 608-575-3029.

Current P-Day (Early Blight) and Disease Severity Value (Late Blight) Accumulations (Many thanks to Ben Bradford, UW-Madison Entomology; Stephen Jordan, UW-Madison Plant Pathology). A P-Day value of ≥300 indicates the threshold for early blight risk and triggers preventative fungicide application. A DSV of ≥18 indicates the threshold for late blight risk and triggers preventative fungicide application. Red text in table indicates threshold has been met/surpassed. TBD indicates that data is To Be Determined as time progresses. Weather data used in these calculations comes from weather stations that are placed in potato fields in each of the four locations. Data are available in graphical and raw data formats for each weather station at: https://vegpath.plantpath.wisc.edu/dsv/

Location Planting Date 50% Emergence Date Disease Severity Values 6/19/20 Potato Physiological Days 6/19/20
Grand Marsh Early Apr 17 May 18 16 233
Mid Apr 25 May 26 13 178
Late May 6 June 1 10 137
Hancock Early Apr 8 May 18 11 246
Mid Apr 20 May 25 9 195
Late May 4 May 30 6 158
Plover Early Apr 10 May 23 12 205
Mid Apr 20 May 30 6 151
Late May 5 June 1 6 139

Station set up at airport 5/29

Early May 14 June 5 2 107.56
Mid May 24 June 10 2 70.36
Late Jun 1 June 17 0 22.75


We are getting close to threshold of 18 DSVs for early planted potaotes in the Grand Marsh area (16 DSVs on June 19). The accumulations for the past week were very limited due to limited moisture and high heat. PDays are nearing 300 for early planted potatoes in Grand Marsh and Hancock areas.

As a reminder the UW Plant Disease Diagnostic Clinic is open for sample processing, but they cannot take walk-in samples; all must come in the mail or connect with a UW representative to have samples brought directly to the lab. We have a 1-2X weekly drop off from the UW Hancock ARS to Madison. E- mail diagnostics have been on the rise and can be very useful in narrowing causes of challenges in potato and vegetable crops. Please send pics and descriptions to me by email and we can get the dialogue going.


National Late Blight Reports: (https://usablight.org/map/) No new reports of late blight in the US over the past week. Late blight has been confirmed on tomato (FL) and potato (FL and AL) during the growing season of 2020. I will continue to monitor this national database and offer updates here in the newsletter.


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