Pest Profile: White Mould in Pulses

Image credit: Soybean Research and Information Network

Sclerotinia sclerotiorum is a pest of many species across the prairies, not limited to chickpeas, lentils, peas, soybeans, dry beans, and canola. In pulse crops it is commonly referred to as white mould, while in Canola it is referred to as sclerotinia stem rot. White mould appears regularly in crop rotations where canola is also present.

Symptoms

• Beans: flowers and developing pods see initial lesion formation. Mould lesions can also develop when infected blossoms fall onto other plant parts. White fluffy mycelium form and within a week black sclerotia start forming.
• Chickpeas: after canopy closes watery white lesions may form on above-ground tissue, generally starting in leaves and flowers. Infection spreads to girdle stems and on pods, leading to brittle bleached stems and damaged pods. Sclerotia form throughout the mycelia
• Lentils: symptoms are similar as to peas. Mycelia form on plants leading to wilting, infection of the stem and bleaching as the tissues die. Sclerotia form in the mycelia. Infection usually occurs in lodged plants that are in contact with sclerotia in the soil or have plant to plant contact.
• Peas: Above ground plant parts see soft rot occurring. With adequate humidity mycelia form on the leaves, pods and stems. These areas become slimy and premature ripening or wilting occurs. Under drier conditions bleaching and brittle stems are more common. Sclerotia form in the mycelia on and inside the stems and pods. Severe infestations may result in yield loss of 70% or more. Typically processing peas are harvested prior to disease damage.
• Soybeans: In the lower canopy bleached lesions develop on stems, leaves and petioles. Mycelium are visible when conditions are humid. Once lesions form the plants wilt rapidly with plants turning grey and then brown. The pods and infected stems see the formation of sclerotia form on or inside them. Severely infected pods may see mycelia formation on the seeds themselves.

Disease Cycle

Main infection mechanism:

• Sclerotia germinate and produce mushroom-shaped asexual reproductive structures called apothecia
• Apothecia release ascospores into air
• Ascospores spread by wind, infect petals of host plant
• Infected petals drop onto leaves and leaf axils/stems, as well as on pods
• Pathogen grows into plant, lesions formed become bleached and brittle in stems or mycelium form on flowers and pods
• Once in new plant sclerotia begin to form
• At harvest plants are shredded and sclerotia are spread onto soil

Secondary infection mechanism:

• Sclerotia may germinate and produce mycelium, infecting roots and stem bases directly
• Sclerotia start developing in stems
• At harvest stems are shredded and sclerotia are spread onto soil

Management: 

While this disease is common, management varies due to weather conditions and overall range of infestation. Generally economic impacts are minimal if there are scattered infestations, however humid growing regions can result in severe yield reductions. Some soybean varieties have resistance mechanisms, however it remains important to maintain multiple year crop rotations with unsusceptible crops, and to use clean, uncontaminated seed. Wide row spacing and lower nitrogen rates to prevent lodging also aid in reducing the impact of the disease.

Control:

Fungicides are the primary control mechanism for white mould and are highly effective.

References:

https://www.saskatchewan.ca/business/agriculture-natural-resources-and-industry/agribusiness-farmers-and-ranchers/crops-and-irrigation/disease/lentil-diseases-identification-and-management#:~:text=Lentil%20varieties%20classified%20as%20%22resistant,plant%20and%20control%20the%20disease. Date accessed: January 7, 2026

https://albertapulse.com/growing-chickpeas/ Date accessed: January 7, 2026

Chickpea Diseases - Alberta Pulse Growers Date accessed: January 7, 2026

https://albertapulse.com/pea-diseases/field-pea-foliar-diseases/ Date accessed: January 7, 2026

https://pmc.ncbi.nlm.nih.gov/articles/PMC6662107/ Date accessed: January 7, 2026

https://albertapulse.com/dry-bean-diseases/ Date accessed: January 7, 2026

https://albertapulse.com/dry-bean-diseases/dry-bean-foliar-diseases/ Date accessed: January 7, 2026

Canadian Phytopathological Society. Diseases of Field Crops in Canada. Saskatoon : Canadian Phytopathological Society, 2003. p. 159, 178, 187, 204