Diseases of Cauliflower
1.Downy Mildew: Peronospora parasitica
Downy mildew can cause much of a field of milk white cauliflower curds to develop superficial discolored spots that renders the disease damage heads unmarketable.
Conidiophores are erect, dichotomously branched; conidia are broadly oval, ellipsoidal and hyaline.
Mode of Spread and Survival
The fungus penetrates in the soil through oospores in hosts. Secondary spread of the disease is through water and wind borne conidia.
Seed treatment with Metalaxyl (Apron 6g/kg). Foliar spray with Metalaxyl (Ridomil) @ 0.4%
2.Wire stem: Rhizoctonia solani
Wire stem can be a seed problem where cauliflower or other cruciferous transplants are grown crowded together in unsterilized soil or seedling beds. This disease makes the seedlings unsuitable for transplanting since many of the affected plants will die or grow poorly.
The fungus shows branching at right angles near the distal septum in young hyphae. Sclerotia are irregular, brown to black and 5mm in dia. The fungus produces both terminal and intercalary, barrel shaped chlamydospores. In the perfect stage basidia are produced on the host. They are barrel shaped, clavate and have four sterigmata. Basidiophores are hyaline and ellipsoid.
Sterilized soil and seedbed drenches with Copper oxychloride 0.25% will give good disease control