ECONOMIC IMPORTANCE
- Yield loss. During periods of wet or humid weather, yield loss from white mold can be as high as 50%.
- Grade loss. Sclerotia (resting bodies) found in seed can reduce grades.
What are the Symptoms?
- Symptoms occur on all above ground parts of the plants.
- Infected plants show small, circular, dark green lesions that appear water soaked and quickly increase in size.
- White cottony mycelium may be present under very humid conditions.
- Advanced stem lesions become very dry and bleached and stems may appear shredded.
- Hard, black resting bodies (sclerotia) may be found on and in affected tissue.
- Crops may become badly lodged.
What is the Disease Cycle?
- Sclerotia overwinter on or just below the soil surface and germinate when conditions are right to produce small mushroom-like structures.
- The cup-shaped surface of these “mushrooms” produce spores within membranes that rupture when the spores are mature.
- These spores are spread by wind or rain splash to stems, leaves or flowers of susceptible plants.
- Spores that land on and infect flowers can spread the disease to pods and seeds, or to other plant parts when the petals fall and come in contact with leaves or stems.
- Under humid conditions, large amounts of cottony white mycelium are produced which can develop into sclerotia in and on affected tissue.
- During harvest, sclerotia remain in or on crop debris, or fall to the soil surface.
- When disease lesions form on pods, sclerotia can be harvested with the seed only to be planted with that seed the following year.
How is it Controlled?
- Use clean, disease free seed.
- Proper crop rotation using non-host crops such as cereals or corn.
- Deep plowing under of infected crop debris (to 8 cm) will prevent the germination and encourage the decay of sclerotia.
- Control of broad-leaved weeds, many of which are susceptible to the disease.
- Use semi-leafless varieties of seed if available to improve air circulation under the canopy.
- Fungicide sprays may be considered if weather conditions are favorable to the disease.
How Does 20/20 Seed Labs Inc. Test for Sclerotinia White Mold in Pulses?
Purity test
- 20/20 Seed Labs Inc. routinely checks for and reports the presence of sclerotia during a seed purity test.
Culture test
- 200 seeds are surface sterilized to remove surface contaminants from the seed coat then placed on culture agar plates and incubated for 7 days.
- A qualified staff member examines the plates presence of Sclerotinia sclerotiorum. The type of mycelium produced and the presence of sclerotia forming on the plate identify this fungus.
- This test gives the percentage of infected seeds to 0.5%.
- This test takes 7 days to complete.
Combined tests for botrytis, ascochyta, anthracnose and sclerotinia are available at reduced rates, depending on the number of disease tests requested.
Please contact us for more information.
