ISSUE #423 Cercospora Management More Important Than Ever

423 - Cercospora Management More Important Than Ever

7-8-02

Cercospora leafspot can cause losses of 2-10 tons per acre in yield and 1-3% loss in sucrose content. Fields with uncontrolled cercospora leafspot can lose $50, $100, even $200, or more in revenue per acre.

American Crystal Sugar Company grower practices records for 1999 show its critical to keep cercospora under control, figure 1. Revenue per acre increased with each fungicide application up to a total of four applications for the season. Late planted beets will have a delayed date of first fungicide application, but may still require 2, 3, and in some cases four fungicide applications. 

423.1

Beets planted May 2nd had $115/acre increased revenue when sprayed three times versus once. Beets planted May 30th had $85/acre more revenue when sprayed three times instead of once.

Beginning the Spray Program:

The 2002 crop varies tremendously due to planting date, replanting date, wind, water, stress and flooding. Many factors need to be considered as cercospora management strategies are planned.

  • Disease incidence and severity in the area is most important.
  • Apply the first spray when disease is found in your township or piler district.
  • Scout or spray fields adjacent to 2001 beet fields earlier.
  • Scout or spray fields on short rotations earlier.
  • Scout and spray fields with less leafspot resistant varieties earlier.

Cercospora resistance Management:

  • Use recommended rates of fungicides (don’t cut rates).
  • NEVER use the same fungicide back-to-back
  • NEVER use the same class of fungicide back-to-back.
  • Apply only one fungicide in the strobilurin class in a given year.
  • Use only the 5-oz. rate of tin fungicides.
  • Only use Topsin once and in a tank mix.

Know The Fungicide Classes:

ClassProductPreharvest Interval
Strobilurin GEM 21
Quadris 0
Headline (not yet registered) 7
Sterol Inhibitors (Triazoles) Eminent 14
TPTH Supertin 7
Agri Tin 21
EBDC Dithane 14
Manzate 75DF 14
Penncozeb 14
Manex 14
Others 14
Benzimidazole Topsin M 21