Disorders in cole vegetables are caused by non-pathological reasons such as poor light, weather damage, water-logging or a lack of nutrients, and affect the functioning of the plant system. The major disorders in cole vegetable crops and their management are discussed below.
CAULIFLOWER & BROCCOLI
1. Brown-rot or Red-rot
This disorder is due to boron deficiency. Water soaked areas are formed in the centre of curd and the affected plants have hollow stems.
Correction measures: Application of borax @ 10-15 kg/ha minimizes the incidence of brown rot.
This disorder is caused due to the deficiency of molybdenum occurring mostly in acidic soils where pH is below 5.0. Leaf blades do not develop properly and remain strap like and severely savoyed. In several cases only midrib develops. The growing point is severely deformed and hence does not produce marketable curds.
Correction measures: Application of about 1-1.5 kg Sodium or Ammonium Molybdate per hectare or raising the pH of soil to 6.5 by liming. Spraying of 0.01% Ammonium or Sodium molybdate on plants.
Magnesium deficiency especially on acidic soil causes yellow mottling of older leaves.
Correction measures: Application of magnesium oxide @ 300 kg/ha.
Development of very small sized 'curds' or 'buttons' while the plants are still small. Probable causes include transplanting of over aged and weak seedlings, inadequate supply of nitrogen in the nursery and in the main field, hot and dry weather, use of poor quality seeds, inadequate moisture supply and improper plant protection measures and crowding of plants or late planting etc.
Surface of the curd becomes loose and has velvety appearance due to elongation of pedicel. Apart from fluctuating and unfavourable temperature, heavy application of N and high humidity may cause riceyness.
Correction measures: Selection of proper varieties for a particular time of cultivation, optimum application of nitrogenous fertilizer and planting of resistant and tolerant varieties.
6. Hollow Stem
In heavy nitrogen fertilized soils, rapidly growing plants of cauliflower develop hollow stem and curd.
Correction measures: Adopt close spacing and use optimum dose of nitrogenous fertilizers.
Curds become leafy due to the growing of small green leaves between the curd segments. This appears due to unfavourable weather conditions.
During early stages of plant growth, damage to growing point by insects, low temperature or frost causes blindness. Such plants fail to form any curd. Leaves become thick and leathery.
Correction measures: Avoid damage of growing point by insects by proper spraying of pesticides.
1. Tip burn:
It is the common physiological disorder of Chinese cabbage in which leaf margin rot due to calcium deficiency. It is also found in cabbage. Affected tissue may be invaded by secondary pathogens, which can cause further breakdown. Inhibition of calcium absorption from the soil due to high salt and NH4 form of nitrogen concentration or high moisture tension induce this disorder. High fertility, especially nitrogen, promotes rapid growth and, consequently, tip burn development. Maintenance of uniform soil moisture by supplementary irrigation during times of moisture stress may be beneficial.
Correction measures: Most effective control of tip burn is development of resistant/ tolerant varieties. Apply calcium.
About Author / Additional Info:
Working as a Senior Scientist at ICAR-Indian Agricultural Research Institute, Pusa, New Delhi