Sunflower Necrosis Disease

Seasons:

•     The low incidence is seen in kgarif (10%), moderate in rabi (10-15%) and high in summer (upto 40%) sown crops.
• The incidence and spread was ow during rainy season.

Stage of the Crop:

• The disease was observed at all growth stages of the crop (seedling to maturity).
• The disease was found to be more severe on parental lines in the seed production plots.

Symptoms:

Vegetative stage:

• Necrosis (death of the tissue) on part of the leaf lamina near the midrib resulting in twisting of the leaf.
• Necrosis (black streak) extends through one side of the lamina to the petiole and stem and finally terminate at shoot of the plant leading to partial paralytic symptom.
• The tip of the growing plant become necrotic giving typical bud necrosis symptoms , the plants fail to produce flowers and finally die.
• Few aggected plants continue to show necrosis on young leaves, whereas few other plants after infection show mosaic mottling symptoms with rough and narrow leaves.
• Few affected plants which showed stunting after infection recovered and later become normal.

Flowering stage:

• Necrosis at bud formation stage lends to partial twisting of the capitulum.
• Necrosis on bracts and back of the capitulum as common.
• Opening of the flower head, expansion of capitulum and seed filling are affected depending up on the stage at which the flower bud/capitulum got infected by necrosis.
• Similar symptoms were observed on weed hosts like, parthenium hysterephorus, Xanthium stromarium, Agrimene masicana and water Melon, surrounding sunflower crop.

Mode of Transmission:

• The disease is transmitted by mechanical sap inoculation under laboratory conditions.
• Studies indicated that white fly (Bemisia tabaci), aphids  (Aphis craecivera, Myzus persicae) do not transmit the disease.
• Thrips (the vector of similar virus disease on water melon, groundnut etc.)suspected to act a vector or sunflower necrosis disease.
• Transmission through sees was not observed.

Management of the disease:

• Uproot and destroy the infected plants as soon as they are noticed in the field.
• Remove the weeds both in and around the fields preferably before sowing.

Prophylactic spray at 15 days interval with systemic insecticides like Dimecron (0.1%) or Imidacloprid (Confidoe) (0.1%)to control possible insect vectors after sowing.

• The planting of 3-4 rows of sorghum/maize all round the sunflower fields is also reported to reduce the incidence of the disease as experienced by the commercial seed growers.

Pre-sowing:

Remove the weeds and self crops, in and around fields.

Sow sorghum (3 to 4 rows) as a border crop.

Treat the seeds with Imidacloprid.  4 g/kg of seed to protect the crop from insect vectors during early stage of the crop.

Post-sowing:

Keep the plots weed free throughout the growing period.

Monitor the fields frequently (every alternate day) for the incidence of the disease.

Carefully uproot and destroy by burying the infected plants as and when noticed in the field.

Prophylactic sprays (3 to 4) at 15 days interval starting from 15 days old seedling to 50 % flowering stage with systemic insecticides like, Phosphamidon (0.1%) or Imidocloprid (0.1%) or Metasystox (0.2%) to control the insector vectors.