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637 - 2024 Cercospora Control Recommendations

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Want higher recoverable sugar/acre potential and better Cercospora Leaf Spot (CLS) control? Initiate your Cercospora fungicide program just prior to row closure.

Crop year 2023 set a lot of records for sugar production: Highest recoverable sugar/acre; highest tons/acre; lowest sugar loss to molasses; 2nd highest sugar %; 2nd highest recoverable sugar/ton. There were a lot of variables that came together to make that crop. One important component to not overlook is that 2023 had the earliest average initial fungicide application for Cercospora control on record so far which added to the overall 2023 crop potential.

Since 2021, Agriculturists have taken early leaf samples weekly from 168 locations throughout the Red River Valley. By the 1st week of July each of the last 3 years, nearly 100% of the locations, North to South, are identified as being positive for Cercospora infection by Dr. Wyatt’s lab at the USDA. This is before visual spots are even present.

Cercospora has adapted to be in full force to infect sugarbeet leaves just prior to row closure, taking full advantage of the optimal environment the closed canopy provides. It can take 5 to 21 days for spots to appear after infection occurs. This is why it is critical to make the initial fungicide application at row closure which normally occurs from the 3rd week of June to 1st week of July, depending on the crop year. This reduces and delays the onset of Cercospora becoming established in the field.

You can’t catch up once Cercospora becomes established. Fungicides are protectants and they don’t cure crop infections. Think of other crop fungicide protection programs. It isn’t recommended to wait to spray fungicide in wheat until we see scab; or in soybeans until we see white mold, or in potatoes until we see late blight. It’s too late then. Why should Cercospora control in sugarbeets be any different?

Dr. Wyatt’s lab also analyzed samples taken by Agriculturists during the growing season between fungicide applications. This revealed resistant CLS population shifts occur in response to the fungicide applied and increase the prevalence of susceptibility to the next fungicide applied in sequence with a different mode of action. This stresses the importance of tank mixing and rotating fungicide modes of action.


RRV Initial CLS Fungicide Application and # of CLS Fungicide Applications

The below charts are compiled from data collected by American Crystal Agriculturists from growers on their Cercospora fungicide application programs from 2019 – 2023 for the Red River Valley.

  • Your Agriculturist has these same charts for their factory district and their growing area.
  • The trends are the same for these as compared to the Red River Valley.
    The charts below show increases in recoverable sugar/acre and revenue/acre with earlier initial fungicide applications and with additional fungicide applications.

The charts below show increases in recoverable sugar/acre and revenue/acre with earlier initial fungicide applications and with additional fungicide applications.

Timing the start of your Cercospora Leaf Spot Spray program.

  • Initial fungicide timing for both CR+ and non-CR+ varieties are the same.
  • Be prepared to start as early as the end of June to the 1st week of July.
    • ACSC data shows, in general, that recoverable sugar/acre and revenue/acre are optimized when starting fungicide applications in this time frame.
  • Start early and stay on track.
    • Fungicides are protectants and are not curatives, use them as such.
    • Limit CLS infections and year-end disease severity with proactive fungicide applications to protect the sugarbeet leaves before infections can occur.
  • Factors contributing to a conducive environment for CLS development:
    • Moderate to severe Daily Infection Value’s (beginning June 15th).
    • Sugarbeet leaves 4” from closing the row.
    • Free moisture on leaves (rain/dew).
  • For CLS control and resistance management, ACSC’s fungicide tank-mix recommendations combine 2 different modes of action which also pairs a translaminar/systemic fungicide with a contact fungicide.
    • Exception is when EBDC is alone in the 5 & 6 spray programs.
      • There is no documented resistance to EBDC fungicides


CR+ Management Considerations

  • CR+ has higher CLS tolerance, NOT immunity.
  • Keep CR+ fields disease free to withstand late-season CLS outbreaks (Sept. & Oct.).
  • Maintaining a healthy late-season canopy:
    • Continues providing energy for sugar & yield growth.
      • Especially through extended heat shutdowns.
    • Protects and provides faster recovery from frost events.
  • CR+ high tolerance allows planning of fungicide timing around forecasted rain events.
  • CR+ resistance management is still necessary to:
    • Preserve CR+ trait’s effectiveness.
    • Preserve fungicide efficacy.
    • Decrease CLS inoculum.
  • Placement of CR+ Varieties:
    • Fields not planned for prepile deliveries.
    • Field bordering last year’s beet fields.
    • Fields protected from wind (higher humidity)
      Ex. river fields & shelter belts.
    • Farther away field difficult for timely fungicide.

Work with your Agriculturist for proper Cercospora fungicide timing based on environmental conditions and crop development.


2024 ACSC Cercospora Recommendations


Tips for Maximizing Cercospora Leafspot Control

  1. CLS variety rating – CLS control should improve with a better CLS variety rating. However, this may not equate to fewer fungicide applications.
    Variety Selector CLS Ratings
  2. Daily Infection Values – Beginning June 15th Monitor Daily Infection Values (DIV’s) and weather forecasts for timing initial and following fungicide applications @ NDAWN
  3. Timing of fungicide program – Start program once rows are 4” from closing and coinciding with Moderate to Severe DIV’s. Start early and stay on track. Cercospora Leaf Spot can appear 5 to 21 days after spore infection. Fungicides are protectants, being proactive by applying fungicides ahead of infection limits the development of Cercospora leaf spot.
  4. Full rates – In tank mixes utilize full application rates of each tank mix partner, following label recommendations.
  5. Spray intervals – The time interval between applications should not exceed 12 days, plan best as possible around adverse weather conditions (rain, wind, hail). For EBDC’s alone follow a 7-day spray interval. CR+ “Extended Intervals” should not exceed 21 days.
  6. Aerial application – If too wet for ground application, stay on schedule with an aerial application.
  7. Glyphosate tank mixes – Are not recommended with CLS fungicide applications since optimum water volume requirements are different for glyphosate and CLS fungicide applications as the target pests are not the same.
  8. Pre-Pile & Fungicide Pre-Harvest Intervals – Be aware of each fungicide’s Pre-harvest Interval and how that may impact pre-pile harvest plans. Adjust your fungicide spray program accordingly.
  9. Water volume – CLS fungicides need excellent coverage to protect the sugarbeet leaf surface. To achieve this requires a minimum of 15 to 20 gallons of water per acre. More water is better!
  10. Pressure – High pressure applications at 80+ psi provides improved leaf coverage depending on the spray tip chosen.
  11. Spray nozzles/tips & droplet size – Using nozzles that will produce Medium droplet sizes of 250–350µm (microns) is optimum for fungicide applications. Utilize nozzle manufacturer’s recommended application pressure to operate within this range. Use proper spray boom height above crop canopy depending on chosen spray nozzle degree angle for best coverage.
  12. Tank mixes – All fungicide applications should contain more than one chemistry or mode of action (MOA). Only exception would be EBDC’s. Tank-mixing fungicide MOA’s and rotating MOA’s are paramount. Using only a single fungicide, MOA, increases resistance development pressure to that fungicide. Single fungicide applications may “get you by” but will increase and compound resistance to fungicides on your farm and surrounding neighbors. Utilizing all available fungicide chemistry wisely is vitally important for current fungicide options today and tomorrow. Any tank mix should be sprayed out as soon as possible, with agitation. Do not allow mix to sit overnight, spray tank out completely, and rinse sprayer (all lines and tank) with clean water daily.
    • Wales tank mixing order for Pesticides

      1. Wettable powders & dispersible granules
      2. Agitate tank to mix thoroughly
      3. Liquid flowables & suspensions
      4. Emulsifiable concentrate formulations
      5. Surfactants & Solutions

  13. Water temperature – Warm water is best for dissolving & mixing fungicides. Pre-warm water in dark bulk tanks a few days prior to use, sunlight aids in warming the water.
  14. Jar test – If in doubt about a tank mix, run a jar test to see if combination is compatible before loading sprayer.
  15. Scout fields – during the growing season to evaluate how your fungicide spray program is working.