Broccoli Diseases

Damping Off

Disease symptoms:

• Damping off occurs in two stages, i.e. the pre-emergence and the post-emergence phase.
• In the pre-emergence phase the seedlings are killed just before they reach the soil surface.
• The young radical and the plumule are killed and there is complete rotting of the seedlings.
• The post-emergence phase is characterized by the infection of the young, juvenile tissues of the collar at the ground level.
• The infected tissues become soft and water soaked. The seedlings topple over or collapse.

Favourable Conditions:

• High humidity, high soil moisture, cloudiness and low temperatures below 24° C for few days are ideal for infection and development of disease.
• Crowded seedlings, dampness due to high rainfall, poor drainage and excess of soil solutes hamper plant growth and increase the pathogenic damping-off.

Survival and spread:

• Primary: Soil, Seed, Water
• Secondary: Zoospore through rain splash or wind

Club root of crucifers or Finger and toe disease

Disease symptoms:

• Stunting and yellowing of plants
• Leaves become yellowish and wilt on hot days.
• Club like swelling of root and rootlets
• Club root is particularly prevalent on soils with a pH below 7, whereas it has been observed that the disease is often less serious on heavy soils and on soils containing little organic matter.

Survival and spread:

• Primary: Soil borne resting spores, which survive for longer periods in soil (10 yrs.) Collateral hosts: Broccoli, Brussels sprout, cabbage, cauliflower, Chinese cabbage, mustard, raddish, turnip
• Secondary: Resting spores or zoospores carried through irrigation water or by root contact.

Favourable conditions:

• It occur at a temperature range of 12-27⁰C.
• High soil moisture
• Neutral to acidic soils 5-7.0 pH

Alternaria leaf spot

Common on cabbage, cauliflower and mustard.

Disease symptoms:

• Spots are small, dark coloured
• They enlarge, soon become circular with a 1mm in diameter
• Under humid conditions groups of conidiophores will be formed in the spot
• Spots develop concentric rings
• Finally the spots coalesce leading to blighting of leaves.
• Shriveling of seeds and poor germination occurs.
• Linear spots also appear on petioles, stems, pods and seeds

Survival and spread:

• Primary: Mycelium persisting in the seed or as spores on seed or from debris
• Secondary: Wind or insect borne conidia

Favourable conditions:

• Soil temperature of around 28⁰C
• High humidity or persistent dew
• Moist weather with intermittent showers

Black rot

Serious on cabbage, cauliflower, knol-khol and radish

Disease symptoms:

• First appear as chlorotic or yellow (angular) areas near the leaf margins
• Yellow area extends to veins and midrib forming characteristic ‘v’ shaped chlorotic spotswhich later turn black
• Veins and veinlets turn brown and finally black
• Vascular blackening extend beyond affected veins to midrib, petiole and stem
• In advanced stages, infection may reach the roots system and blackening of vascular bundles occurs. Bacterial ooze can also be seen on affected parts
• If the infection is early, the plants wilt and die
• If the infection is late plants succumb to soft rot and die.

Survival and spread:

• Primary : Bacterial cells internally seed borneand soil borne
• Secondary: Bacterial cells dispersed through irrigation water and rain splashes.

Favourable conditions:

• Relative humidity more than 90%
• High soil moisture
• Frequent rains

Downy mildew

Severe in radish, cabbage, cauliflower, mustard and knol-khol.

Disease symptoms:

• Small purplish brown spots on under surface of leaves
• Small, pale yellow angular spots on upper surface of leaves, with downy growth on the under surface. The spots coalesce and the leaves shrivel and dries up prematurely
• In cabbage, these spots expose the heads to soft rot
• Cauliflower curds look brownish
• Stems show dark brown and depressed lesions or streaks which later develop downy growth of fungus.

Survival and spread:

• Primary: Oospores in infected plant debris or in soil
• Secondary: Wind borne and rain splashed sporangia

Favourable conditions:

• It occur at a moderate temperature range of 12-27⁰C
• High soil moisture
• Neutral to acidic soils, pH 5-7.

White rust

Disease symptoms:

• White, shiny raised blisters (pustules) on the lower surfaces of leaves, stems and flowers
• Pustules coalesce to form irregular patches
• The epidermis ruptures exposing white spore mass which gives the pustule a powdery appearance
• Distortion of the floral parts including petals, pistils and anthers due to hypertrophy and hyperplasia
• Plants are malformed

Survival and spread:

• Primary: Oospores in soil and sporangia from perennial weed hosts in the vicinity
• Secondary: Wind borne and rain splashed conidia (sporangia) or autonomous zoospores

Favourable conditions:

• Relative humidity more than 90%
• High soil moisture
• Frequent rains

Disease cycles

Downy mildew

White rust

Alternaria leaf spot

Damping off

IPM for Braccoli

To know the IPM practices for Braccoli, click here.

Source: NIPHM, Directorate of Plant Protection, Quarantine & Storage