ISSUE #441

441 - Another Look at Cercospora Leafspot Control for Financial Gain

7-1-03

Cercospora leafspot control is always more challenging when fields are planted early and disease impacts the crop for a long period of time. Crop potential in 2003 is above average in a great many fields. Shareholders must effectively manage Cercospora to achieve that potential in 2003.

Local Level of Resistance to Fungicides

Agriculturists take 100's of samples for USDA and NDSU analysis each year. Data shows fungicide resistance by section and township. Go to www.crystalsugar.com then "Agronomy," then "Pest Alert" for local information and maps.

Areas With Very High Topsin Resistance

  • Southwest of Grand Forks
  • West of Grafton
  • East of Euclid
  • Near Cummings

Contact your agriculturist for information on resistance levels in the townships and sections where you grow beets in 2003.

Date of Planting Impacts

Net Return/A on Fungicide Investment of Different Planting Dates *
Planting Date Variety
VDH 66240 (KWS 5.13)Beta 6447 (KWS 4.85)Beta 6400 (KWS 4.52)
4/26 $184 $123 $97
5/14 $115 $78 ($1)
5/28 $30 ($12) ($37)

* Dr. Larry Smith, U of Mn, 2002

Cercospora Ratings Near or Over 5.0 Are Considered High
Cercospora Ratings Near 4.8 Are Considered Intermediate
Cercospora Ratings About 4.5 or Less Are Considered Low

  • Varieties with high leafspot ratings gave positive net return/A for all three planting dates for 3 sprays.
  • Varieties with intermediate leafspot ratings gave a positive net return for both early planting dates.
  • Varieties with a low Cercospora leafspot rating gave a positive net return for the early planting date broke even for the mid - May planting and needed only two not three fungicide applications if planted late.
  • Four sprays may be necessary in many early planted 2003 fields.

Fungicide Benefits by Variety at Different Planting Dates*

 Variety
 VDH 66240Beta 6447Beta 6400
Planting Datelbs/A Increased Recoverable Sugar
4/26 1399 1237 923
5/14 1172 696 359
5/28 542 242 166

* Average of three applications of fungicide applied.

Resistance to Fungicides

Remember the Strobilurin fungicides Headline, Gem and Quadris are EXTREMELY susceptible to fungal resistance development. Resistance to one is resistance to the others. Use only one spray of a Strobilurin for Cercospora per season if at all possible

Protect Potential

Many fields planted early have excellent yield potential. A total of 4 fungicide applications may be required on many of these fields in 2003.