White mold of pea occurs worldwide under wet conditions on foliage and stems with excessive vine growth. White mold is caused by Sclerotinia sclerotiorum, a fungal pathogen that has a wide range of host plants including many cultivated crops such as beans, Brassica spp., vegetables, potato, sunflower, soybean, and pea.
The pathogen infects stems, leaves and flowers that are in contact with the ground due to lodging. It produces prominent black sclerotia within mycelium and in cavities of infected stems. Sclerotia can germinate and produce mycelium for infection, but they most often develop apothecia, a sexual fruiting body produced after a period of dormancy. Within the apothecia, asci develop which eventually release ascospores into the air. The disease is most severe at the late growth stage when plants are flowering and the canopy is closed.
Under these conditions, a humid microclimate in the lower pea canopy is produced, that is conducive to disease development. Senescent flowers are considered to be the initial nutrient source for infection. Once infection has started, the pathogen can quickly infect all plant parts.
To control white mold, seed used for planting should be free of sclerotia. Dicarboximide can be used as a protectant fungicide during the flowering stage in fields with known risk of white mold. Pea cultivars with semi-leafless traits may offer advantage for reducing white mold. Rotation with cereal crops, but not with many of the broad leaf crops such vegetables, beans, soybean and oilseed rape, can reduce inoculum build-up in the soil. No resistant cultivars of pea are available although resistance in some plant introduction accessions has been reported.
Source: Grünwald, N. J., W. Chen, and R. C. Larsen. 2004. Pea Diseases and their Management. In Disease Management of Fruits and Vegetables. II. Vegetable Diseases, edited by S. A. M. H. Naqvi and K. G. Mukerji. Dordrecht, The Netherlands: Kluwer Academic Publishers.