Infection with the fungus that causes white mold of bean occurs during or after flowering of the crop. Several filamentous fungi can prevent the colonization of bean flower petals by Sclerotinia sclerotiorum to prevent development of white mold. However, there have been many discrepancies in results obtained from different controlled and field environments with selected isolates of these fungi.
Nine isolates of fungi and two isolates of bacteria that were effective in previous studies were compared against fungicides in field evaluations in Ontario, Canada over two years.
The biological control agents suppressed disease in five of the six trials, and six of nine antagonists suppressed white mold in at least one trial. Only Bacillus subtilis reduced disease in more than one trial. Although the reduction in disease incidence was statistically significant in these trials, it was often too small to be of practical value in crop production. Only fungicide applications gave consistent disease suppression.
These studies were conducted under a range of conditions of disease incidence. Stability analysis revealed that all treatments were less effective when conditions were conducive for disease development. When conditions were highly favorable for disease development, the biological control agents did not control disease, but the fungicides did. These biological control treatments were only effective when environmental conditions were less favorable for disease development.
These results suggest the need to integrate existing disease management practices (mainly fungicides) with biological control when environment conditions are not favorable for the biological control agents to suppress disease.
Boland, G. J. 1997. Stability analysis for evaluating the influence of the environment on chemical and biological control of white mold (Sclerotinia sclerotiorum) of bean. Biological Control 9: 7-14.
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