ISSUE #485

485 - Fungicide Use Strategies For 2006


The 2006 growing season will have a very wide range in planting dates, crop development stages and required Cercospora leafspot management program intensity. One Cercospora management strategy will not fit all situations. Ask your agriculturist to assist you with customized control strategies for each field.

Factors to Consider When Planning a CLS Management Strategy

  • Planting date
  • Diploid versus triploid canopy development differences
  • Variety KWS leaf spot rating
  • Date CLS first found in a field or growing area
  • Inoculum level in an area from previous years
  • Past resistance management history in an area
  • Daily infection values in late June, July, August and early September
  • Plant health benefits and fungicide use Intensity of field scouting
  • Crop Rotation length

Maximizing Profit with Fungicides

American Crystal Sugar Company historical grower practice data and research at NDSU and the University of Minnesota indicate higher revenue per acre is achieved with 3 or 4 fungicide applications. Late season plant health benefits can be realized with a fungicide application 30-45 days before harvest even in the absence of Cercospora on the crop.


Practice Resistance Management to Maximize Long Term On-Farm Profit

Field Samples Collected in 2005 show:

  1. Resistance to Topsin remains very high.
  2. Tin resistance is very low.
  3. The resistance to Eminent is quite high now.
  4. The potential for resistance development to GEM & Headline is high

2006 Cercospora Management Recommendations:

  1. Review resistance data for your area with your agriculturist who has the RRV resistance maps.
  2. Rotate fungicides throughout the season.
  3. Give priority to resistance management whenever compatible with disease control.
  4. Tin fungicides should be effective at about half the cost of Strobulurins and Eminent.
  5. Use one Gem or Headline application per season in one, two, or three spray programs.
  6. Use both Gem and Headline only if four separate fungicide applications are needed in a single season.
  7. With four applications, Gem should be first and Headline should be fourth.
  8. Never use Topsin alone and never more than once per year. It mixes well with Tin.
  9. Eminent should be used only once per season unless in townships with no resistance.
  10. Use enough water volume to maximize disease control with ground sprayers. The minimum use should be 10 gpa, with 15 gpa preferred and no need to exceed 20 gpa.
  11. Spray air systems can do a superior job of application. However, water volumes as low as 3 gpa are too low and are often off label. At least 5 gpa and up to 10 gpa is recommended with spray air equipment.
  12. Cercospora inoculum is as low as it has been since 1998.
    • The amount of inoculum present will determine how quickly disease onset occurs.
    • First fungicide application may be delayed depending on planting date, KWS rating, disease onset and disease infection value data. Fields must be monitored frequently if spraying is to be delayed.
    • Later spray initiation removes the need to stretch spray intervals and increases the chance for a late application which will obtain best late season benefits. 

Late Season Growth Enhancement/Frost Tolerance Benefits

  • Maintaining plant and leaf health during September and October is critical. Up to 35% of total sugar accumulation occurs in these months.
  • Maintaining a good canopy allows for maximum photosynthetic efficiency and light interception.
  • Research by Dr. Larry Smith (NWROC) has demonstrated a late season growth benefit of $75/acre.
  • Research in European Union countries and the UK supports the research of Dr. Smith.
  • Results from American Crystal Sugar Company Grower Practice Database shows a late season growth benefit of $82/acre.
  • Spraying with Headline fungicide 30-45 days prior to harvest triggers the effect.
  • Maintaining a healthy canopy reduces the risk of frost damage.
  • Improving disease control and reducing frost damage puts a better product into storage.