A. Cavity spot It is one of the devastating problems affecting carrots mostly in European countries.
- Cavity spots attack the surface of the roots where the outermost cells of the epidermis rupture progressively.
- There is a deposition of suberin and lignin on the ruptured/injured portion of the roots.
- Further polyphenols accumulate around lesions and as a result there may be secondary infection.
- It is characterized by elliptical lesions present on the surface of the roots.
- Cavity spot generally occurs due to deficiency of calcium and excess of K as K reduces the uptake of Ca.
- It has also been reported that adverse soil weather condition is also responsible for causing cavity spot. The workers reported that brief period of soil anaerobiosis and other unfavorable physical condition of soil such as compaction leads to the deterioration in the root surface.
- Recently, researchers show that cavity spot not only occurs due to reasons mentioned above, but also occurs due to fungus spp. like :
(ii) Pythim ultimum: Most commonly occurring spp. causing cavity spot.
(iii) Pythium salcatum.
(iv) P. violae is responsible for causing limited necrosis whereas the development of symptoms caused by P. ultimum is more progressive with water soaked lesion.
- Proper and balanced dose of fertilizer should be given to avoid cavity spot.
- Good physical condition of the soil is requisite factor for eliminating this disorder.
- Proper water management and irrigation done at correct stage also overcome this disorder.
- Increase in Ca level in growing medium results in increased Ca accumulation in plant and leads to reduction of cavity spot.
- Growing of resistant varieties.
- Seeds should be treated with Thiram, Captan and Bavistin before sowing.
- Appearance of longitudinal cracks on the carrot root is known as carrot splitting.
- Carrot splitting occurs due to genetic factors and other factors which are responsible for carrot splitting. These are as follows:
(ii) Higher dose of N2 especially when given in ammonical form causes more splitting.
(iii) The wider spacing between the plants causes splitting.
(iv) Irregular irrigation and fertigation at the time of root development are also responsible for causing this problem.
- Split carrots had large top in relation to the size of the root than the smooth carrots.
- Its disorder commonly occurs in France.
- This disorder attacks on the roots and numerous brown spots appear in cluster on the surface of roots, the epidermis dries and becomes early accompanied by micro-checks.
- It is more prevalent in soil having fine silt and pH > 8.
A. Pore Extent or Pithiness 1. It damage to the quality of radish, destroying its commercial value.
2. Pithiness is formed by the collapse of paranchymatous tissue/cells in root tissue caused by excessive root growth in comparison with the corresponding assimilation ability of leaf tissue.
3. Pithiness is the sign of senescence and its degree varies depending upon the varieties to varieties.
4. Varieties which produce early pores or pithiness have:
(i) Large parenchymatous cells in roots
(ii) More tender basal tissue
(iii) Low starch content.
- The varieties which produce early pores are:
(ii) Earlier enlargement of root, and
(iii) Rapid reduction in TIR ratio (Ratio of root to top ratio).
- Pithiness is characterized by the death of xylem, paranchymatous cells in which gas accumulates.
- It has been reported that pithiness tissue originates from the largest cell which are relatively far from vascular tissue and which are located half-way between centre and epidermis of the root.
- Elongation of root cells may torn apart leading to hollow root.
- It occurs due to delay in harvesting.
- Due to excess N, P and K.
- High temperature prevailing for 3-4 weeks before harvesting is responsible for causing pithiness.
- Over-maturity of roots causes pithiness.
- It has been suggested that variety having large pore development and early elongation of roots might be bred by crossing with variety having early growth/high accumulation ability.
- Harvesting should be done at appropriate time.
- Planting should be done at proper spacing.
- Proper or optimum soil moisture should be maintained in the soil to overcome pithiness.
- Injury to the young roots during intercultural operation also causes forking.
- It is a common disorder in radish and carrots.
- It generally occurs due to excessive moisture during root development.
- Forking generally occurs in heavy soil due to compactness of soil.
- Use of undecomposed organic matter also causes forking.
- It can be overcome by reducing the excess moisture from the field by giving balanced irrigation and proper drainage system.
- Forking can be eliminated by growing in sandy loam soil which is loose and friable in nature.
- Well decomposed organic manure should be used.
B. Irregular supply of moisture also causes this disorder.
D. Akashin Symptoms
- This disorder generally occurs due to deficiency of Boron.
- This disorder is induced by fluctuation in day and night temperature.
- Low soil moisture regime in the soil is responsible for causing this disorder.
- In this disorder, growth of the root is checked.
3. Garden beet
A. Internal black spot (Brown heart or Breakdown of beet)
- It is caused due to deficiency of Boron in neutral or alkaline soils.
- Boron deficient plants remain dwarf and stunted.
- The leaves remain smaller than normal. The leaves may assume a variegated appearance due to development of mixture of yellowish and purplish red blotches over parts or whole, while the stock of the leaves show longitudinal splitting.
- The roots do not grow to full size and under severe deficiency conditions the roots become distorted and very small and have rough, unhealthy grayish appearance instead of clean and smooth. The surface is often wrinkled and cracked.
- Hard and corky black spots are scattered throughout the roots and always found in light coloured zones. The light coloured zones are youngest cells of the beet and are actively growing. Its deficiency first affects youngest cells and tissue.
- Soil application of boron may overcome or surmount the deficiency of boron or this disorder. The quantity of boron may vary from 5 to 50 kg/ha depending upon type of soil, soil moisture and soil reaction.
- Detroit Dark Red variety shows comparatively less symptoms of Bo deficiency.
B. In zoning, alternate dark and light coloured rings are formed on the beet root.
Reason for Zoning Symptoms
- Zoning occurs due to high temperature above 30oC.
- The other reason which causes zoning is wide-range fluctuation in day and night temperature.
- Irregular supply of moisture during root growth and development.
- This disorder of cauliflower is marked by velvetty or granular appearance on the surface of the card..
- Premature initiation of flower bud is characterized by riceyness and is considered to be poor quality for marketing. It manifests in the elongation on peduncle wearing flower buds, granular loose and somewhat velvety.
- Riceyness mainly developed due to temperature fluctuation at the curd formation during warm weather when the crop is closed to maturity and harvesting has been delayed.
- Poor seed stock, heavy dose of nitrogen and high relative humidity also contributes to riceyness.
- Control by cultivation of genetically pure seed.
- Optimum dose of N2 should be applied.
- Use of appropriate varieties with recommended cultural practices.
- Selection of proper variety and transplanting at right time
- . Good seed stock and favorable weather condition tend to prevent this disorder.
- This disorder is commonly seen by formation of small thin leaves from the curds, which reduces the quality of curds.
- Extremely small leaves appear in between curd segment due to heritable or non-heritable factors.
- Prevalence of high temperature during curding aggravates leafiness.
- Browning occurs due to deficiency of Boron.
- Water soaked area in the centre of the curd but in later stage seriously affected stem plant becomes hollow with water soaked tissue surrounding walls of the cavity. In more advanced stage, pinkish or rusty brown areas developed on the surface of the curds, known as brown rot or red rot and causes bitter taste, not fit for consumption.
Symptoms A. Deficiency of Mo causes whiptail syndrome especially in high acidic soil.
B. High Manganese concentration in such soils hinders the uptake of Molybdenum which seldom occurs when pH is 5.5 or higher.
C. The young cauliflower plants may become chlorotic and may turn white along with leaf margins. They also cupped and wither.
D. The leaves blade fails to develop properly and leaves are reshuffled and distorted.
E. In older plants, the lamina of newly formed leaves is irregular in shape and consisting of large bare mid-ribs and hence, the common name is known as 'Whiptail".
Control Measure 1. Molybdenum should be applied in soil @ 1-2 kg/ha or spraying Na molybdate @ 3 g/m2.
Development of small curds with inadequate foliage in cauliflower is known as buttoning. It is also known as premature heading.
Symptoms A. Generally when over-aged seedlings i.e. more than 6 weeks old seedlings are transplanted in the field, it takes more time in establishment due to less developed root system.
B. Planting of early variety late and vice-versa.
C. Hot and dry weather is unfavourable for vegetative growth but favourable for inducing curd formation and inhibits further enlargement and produces button size curds.
D. Buttoning occurs due to inadequate supply of N2.
E. When soil moisture is a limiting factor it checks the growth of the plant which, in turn, causes early formation of curd.
F. When the seedlings are transplanted from poorly managed nursery soil.
- Proper management of nurseries to avoid any check in plant growth.
- An adequate amount of N2 and water should be applied.
- Transplanting should not be delayed.
- Cultural practices should be done in time and water logging and over-crowding should be avoided.
- Care full handling of the plants and good plant protection measure so that the terminal bud may not be injured.
- Exposure of plants to low temperature should be avoided
- Care full handling of the plants and good plant protection measure so that the terminal bud may not be injured.
- Exposure of plants to low temperature should be avoided.
H. Leafiness or bracting: This disorder of cauliflower is indicated by the appearance of green leafy bracts in-between the segment of curd. The main cause of leafiness is prevalence of high temperature than the optimum for a particular variety during curd development.
1. Selection of right variety for the particular growing season.
I. Hollow stem: This disorder of Cole crops is caused due to boron deficiency and or higher supply of nitrogen. Hollowness caused by boron deficiency may be indicated by water-soaked and discolor tissue and if the hollowness is caused due to excess nitrogen, the stem is perfectly clear white with no sign of disintegration.
- Hollowness due to boron deficiency may be control by Spraying 0.25 to 0.50% borax.
- Hollowness due to excessive growth may be controlled by reducing the fertilizer doses and by closer spacing.
K. Black speck: This disorder of cauliflower is marked by the development of black lesions with collapse of cells in interior of the curd of snowball (late) cauliflower. This disorder, though not very common, is caused when snowball (late) cultivars exposed to warm weather at curd development stage.
A. Tip burn: It is the most common physiological disorder of Chinese cabbage in which leaf margin rot due to calcium deficiency. It is also found in cabbage also. It is associated with the death of leaf tissue, usually along the leaf margins in the interior of the head. At first the tissue turns tan or light brown, but later may appear to be dark brown or even black. The affected tissue loses moisture and takes on a papery appearance.. Affected tissue may be invaded by secondary pathogens (i.e., bacterial soft rot), which can cause further breakdown. Because tip burn cannot be detected externally, the head must be cut open to determine whether the disorder is present. Inhibition of calcium absorption from the soil due to high salt and NH4 form of nitrogen concentration or high moisture tension induce this disorder. Tip burn initiation is influenced by plant growth rate because the plant has a high demand for Ca during periods of rapid growth. High fertility, especially nitrogen, promotes rapid growth and, consequently, tip burn development. Well-drained soils with good structure encourage root growth and water and nutrient uptake. The maintenance of uniform soil moisture by supplementary irrigation during times of moisture stress may be beneficial.
Most effective control of tip burn is through the development of resistant varieties. Selection of varieties that have a high level of resistance is difficult, however, because it is impossible to adequately control the environment in the field during that period when susceptible leaves are being formed. Varieties must be evaluated for a number of seasons at several locations before the level of resistance can be reliably determined. To date no varieties have been developed that are completely immune to tip burn, but some varieties do have a high degree of tolerance.
A . Black heart: This occurs due to internal breakdown of tissues in tubers and become black. Lack of oxygen is the probable cause. It is also probable that at high storage temperature (35-40oC) accumulation of CO2 at the centre of the tuber might contribute to damage and the subsequent decrease in respiration and development of black heart. Avoid storage temperature above 35oC and poor ventilation.
B. Hollow heart: Hollow heart consists of an irregular cavity in the centre of tubers. In tissue surrounding the cavity, there is no decay or discoloration. Hollow heart condition appears often in varieties which bulk rapidly and produce large sized tubers. In extra large sized tubers of Kufri Jyoti and Kufri Sindhuri hollow heart may appear. This condition can be avoided by closer spacing of plants and avoiding excessive use of fertilizers.
C. Greening: When tubers are exposed to sun, they develop green colour due to formation of chlorophyll and thus proper earthing up is required in potato
A. In situ Sprouting and Sprouting in Storage - Sprouting is one of the main causes of quality loss during post harvest storage period. The use of chemicals for sprouting inhibition and the use of ionizing radiation will be the alternatives to reduce the losses.
B. Tip Burn - Same as onion.
C.Waxy Break Down -The symptoms are not apparent until the skins surrounding the cloves are removed. Affected cloves are often on the outside of the head, and initially show slightly sunken yellow areas. The entire clove eventually turns amber colored, but remains firm, if slightly shrunken. Waxy breakdown may be associated with poor ventilation and low oxygen levels during storage. Good ventilation during storage may help prevent this problem.
A. Bolting in Bulb Crop - Due to early planting and exposure to inductive temperature. It can be controlled by planting at proper time.
B. Greening - The occurrence of greening is due to exposure of bulbs to sunlight.
C. Splitting and Doubling of Bulb - It may be due to genetic factor or compact soil or due to sudden irrigation after a long dry spell. Loose and friable soil should be used. There should not be long gap for irrigation.
D. Sprouting in Storage
E. Tip Burn -The tips of the oldest leaves first show signs of yellowing and sometimes the symptoms affect the entire leaf. These symptoms are easily mistaken for Botrytis leaf blight, herbicide injury or ozone damage. The cause is believed to be anything that puts stress on the plant and may include heat, drought or fertilizer imbalance. It may be due to calcium deficiency.
About Author / Additional Info:
I am scientist working at Indian Agricultural Research Institute, New Delhi. I am working in the field of agriculture.