ISSUE #499

499 - Cercospora Control - Plant Health - Frost Protection

6-20-07

Cercospora control is no longer the easy straight forward management program it was in the past. Growers must consider resistance management issues, plant health benefits and achieving frost protection during harvest as well. Headline applied in late August has been proven to give significant increases in recoverable sugar per acre in research at the U of MN, in Idaho and other locations. Grower practices data has also shown similar results. Dr. Larry Smith has also shown definite reduction in frost injury with properly timed fungicide applications. Agriculturists also observed frost protection benefits throughout the Red River Valley during frost shutdowns for the 2006 harvest, figure 1. Below freezing temperatures occurred on 8 days from October 9-19 in the field below.

499.1

Planning Your 2007 CLS Management Program

    1. Consider crop rotation length - longer is better because inoculum declines.

    2. Consider variety resistance level - varieties with a KWS rating of 4.4 or less usually require one less spray. Varieties with a rating >4.8 may require an extra spray.

    3. Inoculum levels are low in almost every area of the RRV - don't start too early.

    4. Don't spray too early - wait until CLS is found in your fields or township.

    5. Eminent resistance has declined but is still present - check resistance in your area at our pest alert section.

    6. Strongly consider tin use in 2007 - resistance is not a concern, it performed very well in 2006, and it's less costly too.

    7. Plan your CLS management strategy around a Headline plant health application the last week of August.

Cercospora Control Begins With I.D.

It's not easy to identify Cercospora early in the summer. The photos below compare Cercospora and Bacterial leaf spots.

499.2

Control Recommendations For 2007

  • Base the entire program off a Headline application the last week of August.

  • Do not use any Strobilurin, (Headline and/or GEM,) more than once per season.

  • Never apply Eminent in a one spray program.

  • UM research shows Headline gives greater plant health benefits than GEM.

  • Tilt and Enable (alone or in tank mixes) do not control CLS as well as Eminent and aren't recommended based on NDSU and UM research.

  • Tank mixes of fungicides are not generally recommended until proven effective in further NDSU and UM research.

Choosing a Control Strategy Based on Headline Timing and First Application Date

Fungicide Application Dates
 Dates
Control StrategyJuly - Aug 10Aug 10-24Aug 25-31Sept 1-15
1 Application ----- ----- Headline -----
2 Applications ----- Eminent* Headline -----
2 Applications ----- Tin Headline -----
3 Applications Eminent* Tin Headline -----
3 Applications Tin Eminent Headline -----
4 Applications Tin Eminent Headline Tin
*Don't apply Eminent first in fields adjacent to sections with Eminent resistance in 2005 or 2006.