DISEASES

DISEASES

Fungal Diseases
Damping off: Same as cabbage
Root rot
  • This disease is characterized by severe stunting and rosetting followed by wilting and death of the plant.
  • Lateral roots and cortical tissues of the tap root are severely rotted.
Control measures:
  • Removal and destruction of affected crop and follow crop rotation.
Downy Mildew
  • Light green to yellow areas develop on the leaves which later become brown.
  • Excess moisture enhances this disease.
  • Cos and butter head cultivars are more susceptible than crisp head and leaf types.
Control measures:
  • Spraying of 0.2 per cent zineb can control this disease.
VIRAL DISEASES
Big Vein of Lettuce
  • Yellow discoloration of veins is the primary symptom of big vein.
  • Later, entire leaves become thickened and crinkled.
  • Plants remain stunted and do not form heads.
Control measures:
  • Avoid moist condition of soil and planting susceptible cultivars.
  • Fumigation of the soil with chloropicrin checks this disease.
PESTS
Cabbage Semilooper
  • It prefers lettuce for oviposition and prefers young plants.
Control measures:
  • Apply malathion (0.05 %) and repeat after 10 days.
Aphids
  • These are small in size.
  • Both adults and nymphs suck sap from plant tissues due to which, the plant become weak.
Control measures:
  • Spray malathion (0.05%) or oxy-demeton methyl (0.025 %).
PHYSIOLOGICAL DISORDER
Tip burn
  • The disorder may be caused due to the prevalence of high temperature, light intensity and long duration, excess of nitrogen, deficiency of Ca and B, antigenic age of plant, high Mn and soil moisture content and high endogenous level of IAA.
  • It is characterized by the appearance of tip burning of lateral margins of inner leaves of mature heads.
Correction:
  • Increase the dark period and relative humidity.
  • Spray the crop with CaCl2 @ 0.5 per cent on the standing crop.

SEED PRODUCTION
Climatic requirement
  • Lettuce is an annual cool season crop.
  • It does well in cool growing season with a monthly average of 12-15oC.
  • Its leaves become tough and bitter in hot dry weather.
Land requirement
  • Land to be used for seed production should be free of volunteer plants.
  • The soil of selected field should be rich in organic matter.
Isolation requirement
  • Lettuce is highly self-pollinated, but 1-6 per cent cross pollination due to insects also occurs.
  • At least 50 meters isolation distance for foundation seed production and 25 meters for certified seed production should be maintained.
Time of sowing
  • For seed crops, sowing should be done in October.
Method of sowing
  • The seeds may be sown in raised nursery beds in rows 3-4cm apart, and seedlings later transplanted at a distance of45 × 30-45cm, when they are 5-6 weeks old.
  • Apply well-rotten farmyard manure @ 200-250 quintals, 60 kg phosphorus and 50 kg potash per hectare at the time of preparation of land.
  • Nitrogen @ 60kg per hectare is to be applied in three splits. First part is applied at the time of field preparation and remaining two parts are applied each at six weeks interval.
Irrigation
  • Irrigation should be given as and when needed to maintain uniform soil moisture conditions in the soil.
Rouging
  • Off types plants at vegetative growth stage,
  • During flowering for early and late bolters.
Harvesting and threshing
  • Lettuce seeds ripen unevenly and fully mature seed shatter readily.
  • It is advisable to harvest when 30-50 per cent of the seed in the heads show white pappus.
  • The plants are cut by hand and left to dry on the ground for a few days.
  • Latter, the seeds are collected by gently shaking them.
Seed Yield
  • The leafy types usually produce 5 to 6 quintals seeds per hectare.
  • However, the heading type varieties like Great lakes produce only 1.0-1.25 quintals seed yield per hectare.
Last modified: Tuesday, 19 June 2012, 2:10 AM