ISSUE #526

526 - Cercospora Control and Resistance Management

7-14-09

526The 2009 Cercospora control program will be built around the late season disease control and health benefit of a Headline application. The health benefit of Headline is too great to use any other way and frost tolerance is vital to beet receiving and pile storage. Dr. Larry Smith's research data indicates the best balance of health benefits and frost tolerance is realized with applications the last week of August or very early September.

Q. What if fungicide needs to be applied in late July or early August?

A. The first application should be one of the Triazole fungicides (Proline, Inspire XT or Eminent). In fields with a history of Rhizoctonia, Proline may be the fungicide of choice due to its activity on Rhizoctonia.

The Triazoles are the most effective of the fungicides for control of Cercospora. They should be used in the time frame where the disease is most likely to be spreading.

Q. If a fungicide application is needed in mid-August and one of the Triazole fungicides has already been applied, what should be used?

A. This application should be a Tin fungicide (TPTH). TPTH presently has a history of lower resistance potential and if resistance does start to develop, it has been demonstrated to be reversible. In 2008 no TPTH resistant isolates were found. University trials have shown good Cercospora control with multiple fungicide treatments that include TPTH in the rotation. TPTH will also do a good job of controlling any Cercospora strains that are developing resistance to the Strobilurin or Triazole fungicides.

Q. What should be used in a 2 spray program?

A. The fungicide chosen to be applied in early to mid-August should be Proline, Inspire XT or Eminent. Follow with Headline in late August.

Q. What should be used in a 4 spray program?

A. Use a Triazole then Tin, then Headline and Tin as the 4th spray.

Q. Can I use Headline more than once per year?

A. Multiple applications of Headline accelerate the development of disease resistance. Cercospora sensitivity to Headline remains relatively stable, but there are rare isolates identified with a decrease in sensitivity to Headline. Use Headline only once per year.

Q. Should I apply Headline in late August even if incidence and severity of Cercospora is low?

A. Yes, the plant health and frost benefits are definitely worth it.

Other Considerations: 

  • July applications of Headline show no health benefit or increased frost tolerance.

  • Gem provides good Cercospora control but has less health benefit than Headline and is not recommended. 
  • Apply only one Triazole (Proline, Inspire XT or Eminent) per season and only when a follow up treatment is planned. Multiple applications of Triazole fungicides accelerate the development of disease resistance. 
  • Tank mixes of fungicides other than TPTH plus Topsin are not recommended in 2009. 
  • Stretching application intervals or making the first application of fungicides too late greatly reduces disease control. 
  • Care should be taken to maintain the correct pre-harvest intervals for each fungicide. 
  • It appears that the fungicide resistance management plan that we are following is working since resistance is stable and there have been no fungicide failures in our area due to fungicide resistance. 
  • Alternation and combination of fungicides with different modes of actions will continue to be necessary to prevent reduced sensitivity of Cercospora to currently registered fungicides. 
  • Cercospora Resistance maps can be found here.
  • Contact your Agriculturist with questions about Cercospora control, fungicide resistance and plant health.  

Label Specifications for Proper Fungicide Use *

FungicidesREI - HoursPHI - DaysWater Volume - Gal.
AgriTin 48 7 At least 15
Eminent 12 14 5 or more
Gem 12 21 Minimum 10
Headline 12 7 Sufficient water to ensure thorough coverage of foliage
Inspire XT 12 7 15 is recommended
Manzate, Penncozeb 24 14 Minimum 10
Proline 48 7 Minimum 10
Super Tin (4L), Super Tin (80WP) 48 7 At least 15
Topsin 4.5L, Topsin M WSB, Thiophanate Methyl 85 WDG 12 21 5 or more

* Best results with ground application are to apply 10-15 gpa.

Zone Fertility Management

Make plans now for your zone soil sampling and variable rate fertilization for 2010. A 3-year average revenue increase from zone management is $52/acre