Disturbance in the plant tissue metabolic activity and environmental variables like temperature, light, aeration and nutritional imbalances resulting disorders in the fruit crops. In fruit crops, the deficiency of micro-nutrients just like Zn, Bo, Mn causes many more disorders than that of macro-nutrients.
1. Physiological disorders of Mango:
Spongy Tissue in Mango:
It is a major problem in Alphonso, It is a physiological disorder in which fruit pulp remains unripe because of unhydrolyzed starch due to physiological and biochemical disturbances because of high temperature, convective heat and post harvest exposure to sunlight.
Use of mulching and post harvest exposure to low temperatures between 10-15 C for 10-18 hours has been useful in reducing the malady.
Biennial Bearing in Mango:
This is one of the most burning problems since it renders mango cultivation less remunerative to the growers. Biennial bearing is also known as alternate bearing. It indicates yield variations in alternate years i.e. an year of optimum or heavy fruiting followed by a year of little or no fruiting.
The problem of biennial bearing is a varietal character governed by genetic makeup, and this tendency starts exhibiting in mango plant even at the second year of fruiting and become more serious as the age advances.
Proper upkeep and after care of orchards, adequate manuring and proper irrigation after fruit set can help in reducing irregular/erratic bearing in mango. Soil drenching with paclobutrazol (5-10g tree) results in minimum outbreak of September to October flushes, which results in early and profuse flowering.
It may be applied every year for regular fruiting, particularly in young trees. Ringing of branches is recommended as means of inducing flowering in the 'Off' year. Ringing should be done in August or early September, well before the time of fruit-bud differentiation.
It involves removal of 1 cm wide ring of bark on a branch of about 15 cm thickness. Ringing stops vegetative growth and results in accumulation of carbohydrates and other metabolites in the portion of the branch above the ring, thereby creating physiological condition for flowering.
Fruit Drop in Mango:
In mango, there is a heavy drop of hermaphrodite flowers and young fruits amounting to 99% or more.The commercially grown varieties, Langra and Dasheri are more susceptible to drop in the month first three weeks of April. The fruit drop is more or less a continuous process and can be classified into three phases, viz. (i) pinhead drop, (ii) post-setting drop and (iii) May-month drop. The fruit drop in first two phases are insignificant compared to the third phase which affects the final yield significantly and needs more attention.
Regular irrigation during fruit setting and development period can reduce this problem. application of plant bio-regulators like NAA 40 ppm and 2,4 D 20 ppm at 6 week after fruit set, reduce fruit drop considerably. Single spray of NAA or 2,4-D each at 20ppm or Alar 100ppm at pea stage of fruit gives promising results.
Black Tip in Mango :
Black tip is a serious disorder, Coal fumes of brick kilns containing sulphur dioxide, ethylene and carbon monoxide are observed to be responsible for black tip. The damage has been noticed in the mango orchards located up to 200 metres of distance from brick kiln.
The damage to the fruit gets initiated right at marble stage with a characteristic yellowing of tissues at distal end. Gradually, the colour intensifies into brown and finally black.
At this stage, further growth and development of the fruit is retarded and black ring at the tip extends towards the upper part of the fruit.
Planting of mango orchards in North-South direction and 5-6 km away from the brick kilns may reduce incidence of black tip to a greater extent. The incidence of black tip can also be minimized by spraying Borax (1%) or other alkaline solutions like 2% sodium carbonate.
The first spray of Borax should be done positively at pea stage followed by two more sprays at 15 days interval.
Mango Malformation in Mango:
Mango malformation is of two types viz. vegetative and floral. The vegetative malformation generally affects seedlings of young plants in which there is a swelling of buds and formation of small shoots with short inter nodes at the apical portion and given an appearance of witches broom like structure.
In floral malformation, panicles become deformed, axis become short and rachis thick, due to this inflorescence look like a cluster. Malformed panicles have bigger flowers than the normal flowers and are mostly male.
Spraying of Planofix (200 ppm) during the first week of October followed by deblossoming at bud burst stage is recommended as a remedial measure against malformation. Cutting of the malformed twing alongwith the approximate 15cm healthy portion after complete fruit set in may.
Clustering in Mango ('Jhumka') in Mango:
A fruiting disorder, locally known as 'Jhumka', is characterised by the development of fruitlets in clusters at the tip of panicles. Such fruits cease to grow beyond pea or marble stage and drop down after a month of fruit set. Absence of sufficient population of pollinators in the orchards is the major reason. The other reasons causing the disorder are old and overcrowding of trees, indiscriminate spraying against pests and diseases, use of synthetic pyrethroids, monoculture of Dashehari and bad weather during flowering.
Introduction of beehives in the orchards during flowering season for increasing the number of pollinators and restrict insecticidal sprays at full bloom to avoid killing of pollinators. Pests and diseases should be controlled in time by spraying the recommended pesticides and concentrations.
Spraying of NAA (300 ppm) during October-November is recommended. The practice of monoculture of a particular variety may be avoided. Particularly in case of Dashehari, 5- 6% of other varieties should be planted in new plantations.
2. Physiological disorders Banana
Formation of slitted fingures in Banana
Symptoms are appears longitudinal cracks in fruits this disorder prominent in rainy month occurred immediately after the dry spell.due to the severe water stress,tissue of the fruit get damaged with the absorbtion of water. This damaged tissue tend to expand from cracks.
Chilling Injury in Banana:
Symptoms include surface discoloration, sub-epidermal tissues reveal dark-brown streaks, failure to ripen, and, in severe cases, flesh browning. The discoloration is ascribed to the enzymatic oxidation of dihyroxy phenylalanine.Chilling injury results from exposing bananas to temperatures below 13°C for a few hours to a few days, depending on cultivar, maturity, and temperature.
Choke throat in Banana
It is due to low temperature affecting active growth of the plant. Leaves become yellow and the tissue gets killed. In case of normally flowering plants, the stalk carrying bunches elongates freely so that the entire inflorescence comes out of the pseudostem and hangs down.when the time of flowering synchronizes with low temperature, the bunch is unable to emerge from the pseudostem properly. The distal part of the inflorescence comes out and the basal part gets stuck up at the throat. Hence, it is called Choke throat. Maturity of the bunch is delayed by taking 5-6 months instead of 3.5-4 months for harvest.
Management Provision of shelter belts using Casuarina or Eucalyptus to prevent the effect of cold wind blowing into the orchard and planting low temperature tolerant varieties like Kullan check the disorder.
3. Physiological disorders of Citrus
Fruit Splitting in citrus
It is mainly due to high atmospheric humidity following heavy rains or heavy irrigation during hot weather. Two types of splitting, namely radial and transverse have been noticed. Radial cracking is more common than transverse one. Partial splitting is more prevalent while splitting down to inner core is rather rare.
Often the cracked surface of the fruit gets infected by disease causing organisms such as Aspergillus, Aalternaria, Fusarium, and Penicillum which lead to partial rotting and early fruit dropping from trees.
Proper application of potassic fertilizers, keeping of regular moisture during summer around bearing trees and application of 2-3 sprays of gibberellic acid (10 mg /litre water) during fruit development are some preventive measures for this physiological disorder.
In lime, the spray of 40 ppm NAA after fruit set of monsoon crop (3rd week of May) reduces fruit cracking and improves weight and size of fruit. GA3 10-20 ppm can also reduce fruit cracking to some extent and improve fruit quality.
Fruit Drop in Citrus
The causes attributed to fruit drop in citrus are lack of fertilization, mechanical shock, insects, disease, high temperature, rainfall, and defective irrational practices. The most pronounced stages of fruit drop occurs when the fruits are at marble stage.
For controlling fruit drop in citrus fruits, apply 2,4-D @ 50mg /5 litres of water/tree during April-May and August-September. The spray should not be given at the time when a dicot crop is already standing in the orchard as intercrop
Citrus decline is not a specific disease, but a malady involving complexities of the indistinguishable disorders in the plant. The malady is characterized by stunted growth with sickly appearance, chlorosis and shedding of leaves, dying of twigs, excessive flowering, appearance of sun blotched fruits that seldom mature, rotting of wood and darkening of feeding roots.
Adopting a package of practices such as selection of proper site and soil, raising of genuine and healthy plants from certified bud wood, use of proper rootstock, judicious irrigation and manuring and scientific spray schedule against insect pests and diseases can successfully control the disease.
Granulation in citrus
Granulation is a serious problem of citrus. This abnormality is initiated at the stem end of the fruit which gradually extends towards the stylar end. The affected juice sacs become hard and dry, fruits become grey in colour, enlarged in size,have flat and insipid taste and assume a granular texture. Granulated fruits contain less extractable juice as most of it turns into gelatinous mass.
The incidence of granulation could be reduced to 50 per cent by applying two to three sprays of NAA (300 ppm) in the months of August, September and October. Spraying of GA 15 ppm followed by NAA 300 ppm in October and November also reduce granulation.
4. Physiological disorders of Grape
Water Berries in Grape
Water berry is associated with fruit ripening and most often begins to develop shortly after berry softening. The affected berries become watery, soft, and flabby when ripe. They shrivel and dry by the time of harvest. Such berries mostly confine to the tip of the main rachis or its branches.
Excessive irrigation and nitrogenous fertilizers should be avoided during berry development to reduce the water-berry formation.
Cluster-Tip Wilting of Grape
Light brown lesions on the apical end of the rachis affect the conductivity of the rachis. This results in shriveling and drying of the rachis at the tip of the bunch. In severe cases the tip of the bunch up to 30-40% dries up completely leaving hard small and light brown berries at the tip. Thompson Seedless is more susceptible to this disorder.
Cluster pinching or berry thinning is recommended to reduce excessive crop load on the vines. Ensuring adequate irrigation during the berry development and protection bunches from direct sunlight.
Shot Berries of Grape
They are formed due to delay in pollination and fertilization of a few flowers or due to inadequate flow of carbohydrates into the set berries. Boron deficiency, incorrect stages of GA application and girdling are the known reasons for shot-berry formation.
Similarly application of GA at proper stage should be ensured. Boron or Zinc deficiencies should be corrected.
Pink Berry of Grapes
As the bunch approaches maturity some berries in the bunch develop pink colour at random. The pink colour changes to dull red colour rendering the bunch unattractive.
Indiscriminate use of Etherel for berry colouration can also cause this disorder.
Bud and Flower Drop in Grapes
The malady has been investigated and the association of a number of factors such as, improper nitrogen application, improper fertilization, ambient temperature, heavy crop load,uneven ripening and endogenous auxin deficiency at a particular stage of berry development are reported to cause the malady.
Making 0.5 cm wide girdle from the trunk about 10 days before full bloom which results in better berry set. 500 ppm ethrel at veraison stage should be applied; dipping of bunches in NAA 100ppm 10 days before ripening reduces berry drop, heavy irrigation at bloom should be avoided.
Poor Cane Maturity in Grape:
In this type of disorder shoots fail to mature and their barks remain green until late in autumn. Such shoots turn pink-red due to low temperature in winter. It is more serious in vineyards, where the shoot growth is vigorous and dense; vines are planted closely and excess nitrogen and irrigation are provided.
Judicious shoot pinching to check excessive vegetative growth; shoot thinning 30 days after summer pruning to prevent mutual shading of the shoots and promote light interception are some of the suggested remedial measures. Avoiding excess irrigation and nitrogenous fertilizers during 40-70 days after back pruning helps to overcome cane immaturity.
5 Physiological disorders of Litchi
Poor Fruiting/ Non Fruiting / Irregular Fruiting in Litchi
Poor fruiting/ non fruiting/ irregular fruiting are the problems in litchi growing area of the country.Irrigation, nutrition and environmental factors are also responsible for the cause of irregular bearing in litchi. Type of soil coupled with management practices also found to be associated with irregular bearing or alternate bearing.
Late harvesting and severe pruning and training operations may lead to non bearing in that particular year of operation.
Varieties chosen for planting must be regular in bearing, apart from other desirable characters.The cultivars Shahi, Rose Scented, Dehradun are regular bearer, while China, Seedless and Late Bedana are irregular/shy bearers.
On the basis of age of the trees, the commercial orchards should be properly fed with balance nutrition immediately after fruit harvest and irrigation at right time through right method, particularly at aril development stage.
The plant protection measures to control major pests and diseases should be followed. Proper pruning and training at the time of harvesting and just after harvesting is needed, while harvesting of the fruit bunches, the branches having 8-10 inches length should be plucked to give rise strong and healthy flush to bear fruits in next year.
Late pruning and training should be avoided. The tree should be trained to give canopy shape in a semicircular manner or an open umbrella shape.
Flower and Fruit Drop in Litchi
Sometimes even after profuse flowering and fruit set, poor yield has been observed as because litchi trees suffer a heavy flower and fruit drop between flowering and fruit maturity. Only a small proportion of it (2-18%) is carried to maturity in different cultivars.
The flower and fruit drop is thought to be due to failure of fertilization, embryo abortion, nutrition and hormonal imbalance and external factors like high temperature, low humidity and strong westerly winds as well as due to fruit borer and heavy mite attack. The young bearing tree suffers fewer drops than the older trees.
Honey bees are the main pollinating agent in litchi. Increasing bee population in orchards ensures better pollination and fertilization which increases the fruit set and retention. It is advised not to do any type of spray at the blooming stage of the orchard. Spraying of ZnSO4 @ 0.2% at 30 days before panicle emergence induces healthy inflorescence leading to more fruit set.
Foliar application of 0.2% Boron, 2-3 times during the period of fruit growth and development enhance fruit retention, minimize cracking, improve fruit colour, sweetness and enhance maturity leading to increased percentage of quality production.Two foliar applications of planofix @ 4 ml/5 litre water may be done at an interval of 15 days from peanut size fruits.
Treatment with growth regulators like NAA at 20-30 ppm, GA, at 20-25 ppm, 2,4-D at 10-20 ppm are effective in minimizing fruit drop when sprayed on panicles, before the flower opening.
Fruit cracking in Litchi
It is the most important disorder in litchi found occurring in almost all the important litchi growing tracts. It is a major problem in litchi in India which causes loss as high as 5-70%. This may occur due to varietal characters, orchard soil management, inappropriate levels of water at maturity stage, light, mechanical injuries, and temperature and micro-nutrient deficiency. All cracked fruits lose their value for fresh market and they are used for processing (especially for fruit juice) only. Cracked fruits are susceptible to storage disease, have shorter storage as well as shelf-life.
Selection of site is a most effective way to minimize rain drainage of fruit orchard.To save the cracking problem at maturity stage, fruit plants may be covered only on the top and permit free air flow into the sides.
Mulching can play a big role in stabilizing the temperature and moisture level in root zone. Planting of maize or sugarcane around the litchi orchard and daily irrigation in such border crop creates congenial microclimate which reduces fruit cracking.Application of calcium @ 2 m/l liquid formulations and Gibberellins @ 20 ppm, reduces the activity of cellulose and thereby reduced cracking.
Sprayings of 2,4-D and NAA at concentrations 20 ppm or 20 mg/litre reduces cracking. Boron sprays in the form of Borax or Boric acid @ 2g/l at the initial stage of aril development with enough soil moisture in the root zone checks fruit cracking significantly.
6. Physiological disorders of Pineapple
Multiple Crowns in Pineapple
Ordinarily fruit bears a single crown but in some cases fruit bears more than one. Consequently the top of the fruit will be flat and broad and fruit will be unfit for canning. Such fruits taste insipid and are corky. It is supposed to be a heritable character, found mostly in Cayenne group to which the variety Kew belongs.
Fruit and Crown Fasciation in Pineapple
Fasciated fruits are deformed to such an extent that they are totally useless. In certain cases,proliferation is so extreme that fruit is highly flattened and twisted with innumerable crowns. Fruits and crowns fasciation is associated with high vigour of plants, which take longer time to flower.
High fertility of soil, warm weather and calcium or zinc deficiency may favour fasciation.
Collar of Slips in Pineapple
The collar of slips is typified by the presence of a large number of slips arising from stem close to the base of the fruit, or even directly from the fruits itself. The excessive slip growth is at the expense of the fruit, resulting in small, tapered fruits, often with knobs at the base.
High nitrogen fertilization and high rainfall along with relatively low temperature are supposed to be congenial for such an abnormality.
Dry Fruit and Bottle Neck in Pineapple
The dry fruit and bottle neck fruit types are very similar and may be derived from the same parent. In dry fruit type, fruit is small, flowers are absent and fruitlets do not develop. In bottle neck, lower fruitlets develop normally and upper ones do not develop and give the same appearance as dry fruits. Suckers are freely produced from both the types.
Sun-Scald in Pineapple
This results when plant leans or falls over to one side, thus exposing one side of the fruit to direct sunlight. The cells of the exposed surface get damaged. Later shell surface assumes a brownish to black colour and cracks may appear between fruitlets.
Affected fruits soon rot and become infested with pests. Under favourable climates where leaf growth is luxuriant, leaves can be tied around the fruits to protect them from sunscald. The other method is to cover sun-exposed portion of the fruit with dry straw or grass or with any other locally available materials.
7. Physiological disorders of Pomegrante
Fruit cracking is a serious problem of pomegranate. It is due to boron deficiency in young fruits while in developed fruits it may be caused due to extreme variations in day and night temperatures. At the time of fruit ripening, if the soils become too dry followed by heavy irrigation or rains, cracking may occur.
Delay in harvesting of fully ripened fruits for a long time or severe attack of pest and disease also leads to cracking of the fruits.
The water retention capacity of the plants should be increased by the use of organic manures. The plants should be irrigated regularly during the entire fruit development stage. Spraying of Boron (50 ppm) and GA (40ppm) on the young fruits minimizes the incidence of fruit cracking.
1Vijay Kumar Suryawanshi and 2Neetesh Gupta
2 Horticulture Floriculture and Landscaping, SHIATS ALLAHABAD