Update 8 – June 19, 2022

Amanda Gevens, Chair, Professor & Extension Vegetable Pathologist, UW-Madison, Dept. of Plant Pathology, 608-575-3029, Email:  gevens@wisc.edu, Lab website:  https://vegpath.plantpath.wisc.edu/

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; and our grower collaborator weather station hosts for supporting this disease management effort again in 2022.  A Potato Physiological Day or P-Day value of ≥300 indicates the threshold for early blight risk and triggers preventative fungicide application.  A Disease Severity Value or DSV of ≥18 indicates the threshold for late blight risk and triggers preventative fungicide application.  Red text in table indicates threshold has been met or surpassed.  TBD indicates that data are To Be Determined as time progresses.  Weather data used in these calculations will come from weather stations that are placed in potato fields in each of the four locations, once available.  Data from an alternative modeling source: https://agweather.cals.wisc.edu/vdifn will be used to supplement as needed for missing data points.  Data are available in graphical and raw formats for each weather station at:  https://vegpath.plantpath.wisc.edu/dsv/.

Location Planting Date 50% Emergence Date Disease Severity Values (DSVs) 6/18/2022 Potato Physiological Days (P-Days) 6/18/2022
Grand Marsh Early Apr 5 May 10 13 285
Mid Apr 20 May 15 13 244
Late May 12 May 25 12 186
Hancock Early Apr 7 May 12 13 260
Mid Apr 22 May 17 13 226
Late May 14 May 26 11 182
Plover Early Apr 7 May 15 12 242
Mid Apr 24 May 20 12 208
Late May 18 May 27 11 173
Antigo Early May 1 Jun 3 4 106
Mid May 15 June 15 0 31
Late June 10 TBD TBD TBD

In addition to the potato field weather stations, we have the UW Vegetable Disease and Insect Forecasting Network tool to explore P-Days and DSVs across the state (https://agweather.cals.wisc.edu/vdifn).  This tool utilizes NOAA weather data (stations are not situated within potato fields).  In using this tool, be sure to enter your model selections and parameters, then hit the blue submit button at the bottom of the parameter boxes.  Once thresholds are met for risk of early blight and/or late blight, fungicides are recommended for optimum disease control.  Fungicide details can be found in the 2022 Commercial Vegetable Production in Wisconsin Guide, Extension Document A3422, linked here: https://learningstore.extension.wisc.edu/products/commercial-vegetable-production-in-wisconsin

Our UW Hancock Agricultural Research Station potato field weather station is not properly collecting weather data which drives our Disease Severity Value calculations.  We will be addressing this problem this week.  I utilized the UW Vegetable Disease and Insect Forecasting Network tool to populate the Hancock risk values in the table above.  We are nearing threshold of 18 DSV in Grand Marsh, Hancock, and Plover.  These will likely be met early this week for earliest planted potatoes.  With cooler nighttime temperatures and associated, extended humidity periods the DSVs will accumulate more readily.  According to usablight.org there have not been recent diagnoses of late blight in tomato or potato crops in the US.  For this year, there were just 2 reports entered back in March in southern Florida (US-23 clonal lineage/strain type).

With the stormy weather this past week, some fields took a beating with high winds and blowing sand and rain.  Damaged plants become more susceptible to typically ‘weak’ pathogens (causing diseases such as black dot, bacterial diseases, Botrytis). Damaged fields, even prior to row closure, would benefit from treatment with a preventative fungicide to broadly protect from a range of potential pathogens.  Many of the fungicides registered and routinely used for early blight control are also active on (and registered for) black dot and Botrytis.  For bacterial diseases, the only treatments with some prophylactic control are those containing copper.  Early blight and brown spot are not yet noted in lower canopies in southern Wisconsin, but the activity of these Alternaria species begins typically at the end of June into early July (timing aligned with P-Day 300).  Potatoes are resilient and with more normal summer day temps and cooler night temps, healthy growth will be well supported.


Becky Eddy, Superintendent/Program Manager at UW Rhinelander Agricultural Research Station (ARS); Office Phone:  715-369-0619; becky.eddy@wisc.edu.

UW-Rhinelander ARS Field Day Agenda – July 28, 2022

Location:  4181 Camp Bryn Afon Rd., Rhinelander, WI 54501

  • 9:30-9:35 a.m. Opening remarks – Mike Peters
  • 9:35-9:50 a.m. RARS improvements over the years – Becky Eddy
  • 9:50-10:00 a.m. Timber Management – Manny Oradei
  • 10:00-10:10 a.m. US Forest Service – Ryan Vinhal
  • 10:10-10:20 a.m. GLBRC – Kurt Thelen
  • 10:20-10:30 a.m. Seed Cert Update – Brooke Babler
  • 10:30-10:40 a.m. KFarm Update – Alex Crockford
  • 10:40-11:00 a.m. Travel to field (stop at pollinator plot to say a few words – Becky Eddy)
  • 11:00-11:10 a.m. – Lin Song
  • 11:10 – 11:20 a.m. – Sitonik Chelangat
  • 11:20-11:35 a.m. – Jeff Endelman
  • 11:35-11:45 a.m. –  Amanda Gevens
  • 11:45 -11:55 a.m. – Russ Groves
  • 11:55-12:10 p.m. – Travel back to Station
  • 12:10-1:00 p.m.- Lunch (Sponsor Insight FS)


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