Fennel: Diseases and Symptoms

Leaf (Ramularia) blight

• Symptoms first appear on the lower and older leaves in the month of January, as a minute, angular brown, necrotic spot.
• Later these spots become large and are covered with grayish white erumpent growth.
• At later stage, linear and rectangular spots cover the entire stem, peduncles and fruits.
• Severely affected leaves shrivel and dry up.
• In case of severe attack whole plant turns to brown colour, resulting in drying up of plant

• Pathogen survives on infected plant debris in the soil
• Pathogen infects lower part first and then above plant parts
• It spreads through wind and rain splash.

• Disease favours high humidity >80%.

Leaf spot

• The disease primarily affects older foliage. Affected leaf tips and stems turn brown to black in color and dry up.
• Examination of the stems and leaves show tiny, discrete, dark brown to black fungal patches.
• Early patches are less than one-sixteenth inch wide, and can be oval, circular or irregular in shape

• Primary: Through dormant mycelium remains in the infected crop debris, seeds and volunteer plants
• Secondary: Through wind dispersed conidia

• Disease favours high humidity >80%.

Damping off

• 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.
• Infected seedlings are toppled on the ground surface.

• Primary: Through soil, seed, water
• Secondary: By conidia through rain splash or wind

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

Fusarium wilt

• Disease produces wilting symptoms at seedling and later stage of plant growth
• Infected plants turn yellow.
• Fungal growth may be seen in the infected plant stem if cut longitudinally

• Pathogen is both soil and seed borne and survives as saprophyte in the soil debris as a mycelium and all spore types. It spreads short distances by water splash, planting equipment, and long distances by infected transplants and seeds.
• After the plant dies the fungus invades all tissues, sporulates, and continues to infect neighboring plants.

Favourable condition:

• Soil temperature is between 12.5-14° C and high moisture

Powdery mildew

• The disease symptoms appear at flowering stage in cloudy weather during February-March.
• The powdery fungal growth usually develops first on leaves which later can cover all succulent stems and branches including flowers.
• In severe case seed development may not take place.

• Primary: Through soil and seed,
• Secondary: Dispersal of conidia through wind, rain splashes

• Cool high humid weather (20-25˚ C) or cloudy weather favours conidial germination and disease development
• High RH > 80% favours disease development.

Collar rot

• Disease appears in plots where water stagnation near the plant stem is more.
• Collar portion of the affected plants start decaying and the plants turn to yellow colour & die later on.
• Later collar region of the plant/seedlings get rotted and plant topple down.

• Primary: Dormant mycelium and fruiting bodies survive in the infected crop debris, seeds and volunteer Plants.
• Secondary: Irrigation disperses conidia to nearby plants.

• High humidity, high soil moisture and temperature
• Crowded seedlings

Root rot

• Symptoms consist of seed decay and brown to reddish lesions on seedling stems and roots just below the soil line.
• These reddish brown lesions may become sunken and girdle the stems and kill the plant.
• Plants may often appear stunted and unthrifty and will die.
• Often the stand will appear uneven because of stunted plants.
• Disease is often found in patches in fields.
• On older plants, the pathogen causes a reddish brown dry cortical root rot that may extend into the base of the stem.
• Foliar symptoms may include yellowing or wilting of leaves.

• The disease is mainly soil-borne and pathogen can survive in the soil as sclerotia for several years.
• Sclerotia disseminate by irrigation water, implements, and other cultural operations.

• Dry weather following heavy rains,
• High soil temperature (35-39˚ C)

IPM for Fennel

To know the IPM practices for Fennel, click here.

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