402 - Cercospora Management Success Enhances Crop Quality
At this point in the growing season good stand establishment practices and use of best management practices for weed and insect control provide a solid foundation for 2001 crop yields and quality. Understanding how the sugarbeet crop develops is critical when making Cercospora management decisions. Figure 1 shows how leaf, petiole and root growth changes from planting to harvest of the crop.
Shareholders must maintain a healthy crop canopy from early July to harvest to maximize root development and on-farm profit. Choice of best Cercospora control practices is the last critical management practice shareholders have control over prior to harvest. Grower Practice records from 2000 show the value of effective leafspot control. Losses of up to nearly $175 per acre can occur with only moderate disease pressure if Cercospora reduces root growth in July, 'August and September (Table 1).
Cercospora Management 2001:
A one strategy fits all fields approach is destined to 1) fail to adequately control Cercospora or 2) be excessively costly. Effective disease control and cost efficient leafspot management demands attention be given to the details influencing disease development in each individual field.
Steps to Successful Cercospora Control:
- Timely initiation of fungicide applications
- Management of fungicide resistance
- Choose the correct fungicide and rate to use
- Proper application of the fungicides
Factors to Consider When Beginning the Spray Program:
- The incidence and severity of disease in the area is most important
- Date of planting - spraying late planted or replanted fields can be delayed by a few days to a week or two versus early planted fields
- Distance from 2000 fields with disease. The closer a field is to a diseased 2000 field the sooner it should be sprayed
- Fields in 2 or 3 year rotations need to be sprayed earlier and more often than 4-5 year rotations
- Varietal resistance level:
- Varieties with a leafspot rating near 5.0 or higher need to be sprayed early and more often
- Varieties with a rating of 4.5 or less may enable the first fungicide application to be delayed a few days and might require one less spray for the season
How to Manage Leafspot Resistance:
- Levels of Cercospora Beticola resistance to fungicides has been determined from leaf samples collected by each agriculturist in 2000
- The "Pest Alert" section of crystalsugar.com has detailed maps of resistance by RRV section and township
- Never make back to back applications of any fungicide - NEVER
- Never use Topsin or Benlate more than once per season
- Never use Topsin or Benlate alone, tank mixes are more effective
Eminent Label Changes for 2001:
The EPA approved section 18 label for 2001 states" Eminent MUST be alternated with other fungicides."
- It is illegal for anyone to apply back-to-back Eminent applications in 2001
- It is illegal for anyone to recommend back-to-back
Eminent use in 2001
Proper Fungicide Application Recommendations:
- Lower labeled rates of fungicides must be applied more often at shorter application intervals and higher cost.
- The contact fungicides (tins and mancozebs) require better canopy coverage and higher spray volumes.
- Reduced disease control results when intervals between spray applications exceed label requirements.
- Observe pre-harvest application intervals in late August and September.
Contact your agriculturist, university specialist or go to "Pest Alert" under agronomy at crystalsugar.com for daily infection values, resistance maps, and other information.
2001 Grower Idea Contest
Entry forms for the 2001 contest are available from your agriculturist. Now is the time to take photos and document your good ideas. Over $2,000 in cash prizes available for the top 5 entries.