White mould, caused by Sclerotinia sclerotiorum, is a major disease problem of green beans.
It can cause yield losses by premature plant death through lower stem infection and/or infection of beans. Crops with greater than 8% Sclerotinia are rejected due to difficulties in processing. Benomyl (Benlate) and procymidone (Sumisclex) are the two fungicide products currently registered for use to control Sclerotinia disease on beans.
In recent years, field officers and growers have noted poor control of this disease. It is not clear whether this relates to fungicides used, spray application, crop density, spray timing, fungal resistance to fungicides, or other factors.
- None of the 36 isolates of S. sclerotiorum were found to be tolerant to benomyl or procymidone.
- Sumisclex consistently gave the greatest disease reduction compared to other products evaluated.
- The grower survey findings showed that application methods used by growers are highly variable.
The trials indicated that application methods influenced the level of disease.
- In areas that are prone to Sclerotinia diseases, the timing of the first spray application is likely to be the most important factor in determining the level of disease control.
- The first application, applied at 10% plants with open flowers, gave much better disease control than those applied at 90% plants with open flowers.
- However, in the second field trial, which was conducted in an area not prone to severe Sclerotinia disease, the level of disease control on plants first treated at 10% flowers was similar to those first treated at 90% flowers.
- Spray nozzle types and spray water volume have little or no influence on disease control. An increase in the spray water volume from about 250 to 600 and 700 L/ha, did not cause a significant improvement in the level of disease control.
Horticultural Research & Development Corporation, bean growers, and Crop Care Australasia provided funding for this work.
Technical assistance from Christine Horlock and Pam Cox are also gratefully acknowledged.
The assistance of vegetable growers, Garry McNab of Simplot Australia Pty Ltd, Darren Briggs of McCain Foods and Rob Wilson of Serve-Ag Pty Ltd, is gratefully acknowledged.