When growers bring in peanut samples to County Extension maturity clinics, often they ask about when to terminate fungicide applications. Well, it all depends on their particular disease situation they are facing. Bob Kemerait, UGA Peanut Plant Pathologist, has given some great suggestions to answer these questions..
Below are some typical situations that peanut growers may find themselves in and suggestions for control:
- Grower is 4 or more weeks away from harvest and currently has excellent disease control.
- Suggestion – I recommend the grower apply at least one more fungicide at least for leaf spot control.
- Suggestion – Given the low cost of tebuconazole, the grower may consider applying a tank-mix of tebuconazole + chlorothalonil for added insurance of white mold and leaf spot.
- NOTE: If white mold is not an issue, then the grower should stick with a leaf spot spray only.
- Grower is 4 or more weeks away from harvest and has disease problems in the field.
- If the problem is with leaf spot – Grower should insure that any fungicide applied has systemic/curative activity. If a grower wants to use chlorothalonil, then they would mix a product like thiophanate methyl (Topsin M) or cyproconazole (Alto), with the chlorothalonil. Others may consider applying Priaxor, if they have not already applied Priaxor twice earlier in the season.
- If the problem is white mold – Grower should continue with fungicide applications for management of white mold. If they have completed their regular white mold program, then they should extend the program, perhaps with a tebuconazole/chlorothalonil mix. If the grower is unhappy with the level of control from their fungicide program, then we can offer alternative fungicides to apply.
- If the problem is underground white mold – Underground white mold is difficult to control. Applying a white mold fungicide ahead of irrigation or rain, or applying at night, can help to increase management of this disease.
- Grower is 3 or less weeks away from projected harvest and does not currently have a disease issue. Good news! This grower should be good-to-go for the remainder of the season and no more fungicides are required.
- Grower is 3 or less weeks away from harvest and has a problem with disease.
- If leaf spot is a problem and 2-3 weeks away from harvest, a last leaf spot fungicide application may be beneficial. If leaf spot is too severe, then a last application will not help.
- If white mold is a problem and harvest is 3 weeks away, then it is likely beneficial to apply a final white mold fungicide. If harvest is 2 weeks or less away, then it is unlikely that a fungicide will be of any benefit.
- NOTE: If harvest is likely to be delayed by threat from a hurricane or tropical storm, then the grower may reconsider recommendations for end-of-season fungicide applications.