Major diseases of Mustard are:-
1.Sclerotinia Stem Rot: Sclerotinia sclerotiorum
Symptom:
- The stems develop water-soaked spots which later may be covered with a cottony white growth.
- As the disease progresses, affected portions of the stem develop a bleached appearance, and eventually the tissues shred.
- Girdling of the stem results in premature ripening and in lodging of plants.
- Hard black bodies, the sclerotia, are formed inside the stem and occasionally on the stem surface. Basal stalk infections rarely occur.
- Yield loss of 10 to15% has occurred in Saskatchewan, Manitoba and North Dakota; occasionally losses of 50% have occurred in Manitoba
Management:
- Use crop rotation; do not plant highly susceptible crops more than once in four years, including dry edible beans, sunflowers, mustard and canola. Use at least a five-year rotation for severely infested fields.
- Avoid planting next to a field that had severe Sclerotinia in the past four or five years. Control broad-leaved weeds.
- Plant thoroughly cleaned seed. Avoid dense stands of canola.
2.Alternaria Black Spot- Alternaria brassicae and A. raphan
Symptom:
- The stems develop water-soaked spots which later may be covered with a cottony white growth.
- As the disease progresses, affected portions of the stem develop a bleached appearance, and eventually the tissues shred.
- Girdling of the stem results in premature ripening and in lodging of plants.
- Hard black bodies, the sclerotia, are formed inside the stem and occasionally on the stem surface. Basal stalk infections rarely occur.
- Yield loss of 10 to15% has occurred in Saskatchewan, Manitoba and North Dakota; occasionally losses of 50% have occurred in Manitoba
Management:
- Crop rotation helps reduce disease carry over but does not eliminate airborne spores from another field.
- Clean seed to remove shrunken seed that may be infected with black spot and have low viability.
- Use seed with high germination (over 90%). Swath badly infected crops early to minimise shattering losses and seed shrinkage due to black spot.
3.Mustard White Rust: Albugo candida
Symptom:
- White to creamy yellow pustules develop on the lower leaf surface. The pustules, later coalesce to form patches on the lower leaf surface.
- Tan-yellow spots develop on the upper leaf surface opposite the pustules.
- Pustules may also form on the pods. Infected flowers develop a “staghead” in which the flowers are sterile, malformed and green, and various flower parts may be thick and club-shaped and greatly enlarged.
- Most turnip or Polish varieties of canola, as well as brown and oriental mustard, are susceptible.
- Yield losses are about 1% for each 1% of staghead observed in a field. Yield losses in Manitoba are usually less than 10%.
Management:
- Argentine varieties are resistant. If growing Polish type canola, select resistant varieties.
- See current variety recommendations for information on susceptibility.
- Use at least a three-year crop rotation. Control volunteer canola and susceptible mustard-type weeds in the rotation.
4.Mustard Downy Mildew: Peronospora parasitica
Symptom:
- Leaf spots initially are angular, translucent, light green, later developing into grayish-white irregular necrotic (dead) patches.
- The stems of flower clusters become swollen.
- Frequently associated with white rust. May develop late in the season on turnip-type (Polish) canola varieties.
Management:
- Destroy crop refuse; crop rotation.
Source-
- TamilNadu Agritech Portal
