Physiological Disorders of Mango

The productivity, as well as the quality of fruit crops, is affected to a greater extent due to the physiological and nutritional disorders. Disturbance in the plant metabolic activities resulting from an excess or deficit of environmental variables like temperature, light, aeration and nutritional imbalances result in crop disorders. Micronutrient deficit creates far more problems in fruit crops than macronutrient deficiency.

With the reduced use of organic manures, the adoption of high density planting, the use of root stocks for dwarfing, disease and salt tolerance, imbalanced NPK fertilizer use, and the expansion of horticulture to marginal lands, nutritional problems have become widespread. To get high quality fruit and yields, micronutrient deficiencies have to be detected before visual symptoms are expressed. The deficiencies of Zn, Mn and B are common in sweet orange, acid lime, banana, guava and papaya in India. To correct both visual and hidden micronutrient deficiencies, appropriate foliar and soil applications are necessary. The description of physiological and nutritional disorders in crops include a number of technical terms and it is essential to understand the terms for better identification of symptoms.

Some common terms are, bronzing (development of bronze or copper color on the tissue), chlorosis (loss of chlorophyll resulting in loss of green colour leading to pale yellow tissues), decline (onset of general weakness as indicated by loss of vigour, poor growth and low productivity), die-back (collapse of the growing tip affecting the younger leaves), firing (burning of tissue accompanied with dark brown or reddish brown color), lesion (a localized wound of the leaf/stem tissue accompanied with loss of normal color), necrosis (death of tissue), scorching (burning of the tissue accompanied with light brown color resulting from faulty spray, salt injury etc.).  

Mango malformation  

Thick vegetative stems are produced, and floral portions are transformed into a compact clump of sterile blooms. There are two forms of mango malformations. The first is vegetal, and the second is floral. Vegetative malformation resembles a "bunchy top" that will eventually dry out and die. Floral malformation causes floral growth and the production of additional flowers even after fruit set, but only a small percentage of hermaphrodite flowers. Panicles with malformations can be both loose and compact. Malformation is serious in North than in South. It may result in loss of about 50- 60% crop. Krishnabhog, Collecter, Langra, Neelum are tolerant (seedling trees are found to be tolerant) Virus, fungus, mites, nutrients, C/N ratio, carbohydrates, nucleic acids, amino acids, proteins, phenolic compounds, enzymatic activity in the plant, phytohormones and occurrence of malformation like substance are all supposed to be the probable causes for malformation.  

Contol measures:  

1. Application of plant growth regulators and phenolic compounds (NAA, Ethrel, GA, Paclobutrozol, etc. 

2. Deblossoming: at bud brust stage with the help of Ethrel

3. Use of antagonists and antimalformins like Glutahione, Ascorbic acid, Silver nitrate 

4. Application of nutrients: High NPK added with FeSO4, Cobalt sulphate

5. Pruning of malformed parts. 

6. Application of pesticides: Parathion, Kelthane, Kerathane. 

7. Covering panicles with polythene film to raise the temperature around the panicle. 

Biennial bearing in mango: 

Biennial bearing or alternating bearing refers to a mango that produces a good crop one year and no crop or fewer crops the following year. This is a hereditary trait that is present in all mango types. The main reasons for this are said to be:  

1. Climatological factors: Rain, high humidity, low temperature making on to off year 

2. Age and size of shoots: Shoots of 8-10 months maturity will be productive. 

3. Carbon/Nitrogen ratio: High carbon/moderate N encourages flower bud formation (30- 40) 

4. Hormonal balance: Higher levels of Auxin and inhibitor like substance and lower levels of gibberellins like substances were found to be vital for a flowering shoot.

Black tip  

Physiological disorder causing distal end of fruit to become black hard Polluted atmosphere with smoke, carbon monoxide, carbon dioxide, Sulphur Dioxide, acetylene causes this disorder. Spraying Borax 0.6% from fruit set at 10-15 days intervals controls this (Punjab, UP, Bihar, WB). The damage has been seen in mango orchards up to 200 meters away from the brick kiln. It's identified by depressed spots of yellowing tissues at the fruit's distal end that gradually grow in size, turn brown, and finally black. The necrotic area is always restricted to the tip of the fruit. The growth of the fruit is almost at stand still and the fruit becomes soft after premature ripening. Such fruits never reach full maturity and drop earlier. The preventive measure is to have orchards 1.5km to the east and west and 0.75km to the north and south away from the kilns.  

• Spraying of 2% sodium carbonate or 0.6% borax is recommended as control measure. 

Spongy tissue in fruit  

Spongy tissue is a non-edible sour patch that develops in the mango fruit's mesocarp. Only Alphonso has been affected by the disease. The uniqueness of this disease is that the external indications of spongy tissue-affected fruit are not visible at the time of harvest or at the ripe stage. Only by cutting the mature fruit can these be recognized. The fruit is unfit for human eating as a result of this ailment. Because of hydrolyzed starch induced by physiological and biochemical disruptions caused by heat in mature fruit at pre- and post-harvest stages, the fruit pulp remains unripe.. Single and double Pre-harvest dip of fruits in calcium solution significantly increased the calcium content in the ripe fruits, whereas there was no significant increase in calcium content by post-harvest Ca dip treatment. The pre harvest dip significantly reduced the occurrence of spongy tissue in the ripe ‘Alphonso’ fruits.  

• The preventive measures is to have the use of wind-breaks for protecting the orchard from warm air during May month.

• Use of proper precautions at post-harvest stage checks the disorder. 

Fruit drop  

In mango, there is a heavy drop of hermaphrodite flowers and young fruits amounting to 99% or more. In general, in mango 0.1% or less hermaphrodite flowers develop fruits to maturity. The maximum drop of fruits in ‘Langra’ and ‘Dashehari’ takes place in the first three weeks of April and differs significantly from the drops in the following weeks. Fruit drop is to some extent associated with the variety, as the variety ‘Langra’ is more prone to fruit drop than ‘Dashehari’. The most important internal mechanism causing the post-fertilization decline in mango could be a lack of nourishment for many developing embryos. This occurs as a result of competition among panicle fruitlets that are overloaded. Another cause of decline could be the embryo's degeneration during its early stages of development. If the blooms are self-pollinated, this will always happen. Control measures 

• 2, 4-D produced better results at concentrations below 20ppm, because at higher concentrations fruit and seed development is retarded. 

• Single spray of NAA or 2,4-D each at 20ppm or Alar 100ppm at pea stage of fruit gives promising results. 

Zinc deficiency  

Little leaf, which is caused by a zinc deficiency, is the most common nutritional problem in mango. Roots, shoots, and leaves are stunted as a result. The leaf lamina turns pale yellow, but the midrib remains green.. Leaves become very small, little with interveinal chlorosis. Yellowing, necrotic patches develop on old leaves with drying of leaves. Subsequently necrotic patches turn grey and cover the entire surface. Control measures is to have two sprays of 1-2% Zinc Sulphate, one at the time of flowering and the other at one month after the first spray correct the disorder. 

Authors

Balkesh Kumari¹,Lokesh Kumar²  

¹ Department of Horticulture, Rajasthan College of Agriculture, MPUAT, Udaipur 

 ² Department of Horticulture, College of Agriculture, Agriculture University, Jodhpur