Cultivation of Potato (Solanum tuberosum)

Introduction

Potato (Solanum tuberosum) is being grown as a commercial crop in India since 1830. With the initiation of systematic potato research and the establishment of the ICAR-Central Potato Research Institute, Shimla, in 1949, there had been a phenomenal increase in area, production, and productivity of the crop in the country. In 2013-2014, India produced 44.3 million tonnes of potatoes from an area of 2.0 million ha. Compared to the production figures of 1949-50 (1.54 million tonnes from 0.234 million ha with an average yield of 6.58 tonnes/ha), the increase in area, production, and productivity of this crop had been 8.6, 28.8, and 3.3 times, respectively. India ranked third in the area as well as production in the world in 2013, and contributed 10.2 and 12.3% to the global potato area and production, respectively. Potato is grown in almost all the states in India under diverse agro-climatic conditions. Major potato-growing states in India are Uttar Pradesh, West Bengal, Bihar, Madhya Pradesh, Punjab, Gujarat, Karnataka, and Haryana. These states account for 83% of potato area and 90% of potato production in the country. In 2013-2014, Gujarat recorded the highest potato productivity, followed by West Bengal, Punjab, and Uttar Pradesh.

Table of contents (toc)

Climate and soil

Potato is largely grown in cool regions, where mean night temperature does not normally exceed 18°C in the season. The optimum temperature for potato growth and development ranges between 15-25°C. Minimum night temperature is of great significance for tuberization and 17°C is most favorable for tuber formation. At night temperatures above 18°C, tuberization and yield are reduced. For this reason, the tropics are considered unsuitable for profitable potato cultivation. At low temperatures, the vegetative growth of the plant is restricted and at temperatures near the freezing point, the plants are killed. Therefore, potato is grown as a summer crop in hills (March/April-September) and as a winter crop in tropical and subtropical regions (October/ November-January/February) of the country. The planting time of the potato is adjusted keeping in view the prevailing temperatures. Long photoperiods promote vegetative growth and delay tuberization and maturity, whereas short photoperiods reduce vegetative growth but enhance tuber initiation and crop maturity. For best yields, potato crop needs long day conditions during vegetative growth (early 30-40 days after planting) and short-day conditions during tuberization. Potato can grow in all types of soils, but light, well-drained sandy loam soils are best suited. With adequate fertilizer application, potato grows well even in sand. Heavy soils are difficult to work with and are not well suited for potato production. The potato plant prefers soils in the acidic to a neutral range (pH 5.5-7.5).

Varieties

The major area under potato cultivation in India is covered by varieties Kufri Jyoti, Kufri Bahar, and Kufri Pukhraj. The improved and commercially important potato varieties recommended for different agro-climatic zones in the country are given below:

Improved and commercially important potato varieties

North-Western Plains (Haryana, Punjab, and Rajasthan)

Early (70-90 days) – Kufri Ashoka, Kufri Chandramukhi, Kutri Jawahar, Kuin Khyatd, Kutri Pukhraj and Kulri Surya

Medlum (90-110 days) – Kulri Anand, Kufri Arun, Kulri Badshah, Kuri Bahar, Kut Chipso na-1, Kufri Chlpsona-3., Kufrl Garims, Kufri Gaurav, Kutri Jyot, Kutrni Pukhral, Kulri Pushkar, Kudri Sadabahar and Kufrn Sutlej

North-Central Plains (North-western districts of Madhya Pradesh and Western Uttar Pradesh)

Early (70-90 days) – Kutri Chandramukhl, Kutrl Jawahar, Kutri Khyati, Kutri Pukhra, Kul Lauvkar and Kulri Surya

Medium (90-110 days) – Kutrl Anand, Kutr Arun, Kutri Badshah, Kutn Bahar, Kutri Chipsona-1, Kufrl Chipsona-3, Kufri Frysona, Kufri Garima, Kulri Gaurav, Kufrl Jyotl, Kufri Pukhra, Kufri Pushkar, Kutri Sadabahar and Kulri Sutlej

Late (>110 days) – Kufri Sindhuri

North-Eastern Plains (Plains of Asom, Bihar, Northeastern Madhya Pradesh, Odisha, Eastern Uttar Pradesh, and West Bengal)

Early (70-90 days) – Kufri Ashoka, Kufri Chandramukhi, Kuri Khyati, Kutr Pukhraj and Kufri Surya

Medium (90-110 days) – Kutrl Arun, Kutri Bahar, Kufri Chipsona-1, Kutri Chipsona-3, Kutri Frysona, Kufri Garima, Kufri Gaurav, Kutri Jyou, Kutri Kanchan, Kutri Lalima, Kufri Lalit, Kufri Pukhraj, Kufri Pushkar, Kufri Sutej and TPS Population 92-PT-27

Late (>110 days) – Kufri Sindhuri

Plateau Region (Southern parts of Bihar, Gujarat, Karnataka, Madhya Pradesh, Maharashtra, and Odisha)

Early (70-90 days) – Kufri Chandramukhi, Kutri Jawahar, Kufri Khyati, Kutri Lauvkar, Kufri Pukhraj and Kufri Surya

Medium (90-110 days) – Kufri Badshah, Kufri Garima, Kufri Jlyot and Kutrn Pukhraj

North-Western Hills (Southern Jammu and Kashmir and Himachal Pradesh)

Early (70-90 days) – Kufri Chandramukhi, Kutri Jawahar, Kufri Khyati, Kutri Lauvkar, Kufri Pukhraj and Kufri Surya

Medium (110-120 days) – Kufri Girdhari, Kufri Giriral, Kutri Himalini, Kufri Himsona, Kutri Jyoti and Kufri Shaila

North-Eastern Hills (Hills of Arunachal Pradesh, Manipur, Meghalaya, Mizoram, Nagaland, and Tripura)

Medium (110-120 days) – Kufri Girdhari, Kufri Giriraj, Kufri Himalini, Kutri Jyot, Kutrni Megha and Kufri Shailja

North Bengal and Sikkim Hills (North Bengal hills and Sikkim)

Medium (110-120 days) – Kufri Girdhari, Kufri Jyoti and Kufri Kanchan

South Indian Hills (Hills of Tamil Nadu)

Medium (110-120 days) – Kufri Girdhari, Kufri Giriraj, Kufri Himalini, Kufri Jyot, Kufri Neelima, Kufri Shailja and Kufri Swama

Propagation

Potato is propagated vegetatively using tubers as planting material. Each tuber has several eyes distributed over its surface with each eye having 3-5 buds, which develop into sprouts. When planted in the soil, the sprouted tuber establishes itself into a plant. Each sprout, on emergence above the ground, develops into a stem bearing leaves and branches. Seed tubers account for about 40-50% cost of cultivation and the quality of tuber seed is most important to ensure good crop production. Prior to 1960, potato seed was imported to replace the old seed stocks in the country. Some attempts were also made to produce potato seed in the hills and in Bihar and Uttar Pradesh. Northern hills were the major sources of healthy seeds for planting potato crops in the plains. However, the area in the hills was highly inadequate to meet the total seed demand of the country. Besides, the seed harvested in the hills during September/October used to be in dormant stage at the optimum time of planting (October/ November) of the crop in the plains and the varieties grown under long-day conditions in the hills were often not popular for cultivation under short-day conditions in the plains. In view of these constraints, efforts were made to produce healthy seeds in the plains. Extensive research led to the development of the Seed Plot Technique for the production of healthy seeds in north Indian plains.

Seed plot technique: This technique of seed production envisages raising a potato seed crop during low aphid (vectors of viral diseases) period, use of insecticides, periodic rouging of diseased plants and finally dehaulming the crop before aphids reach the critical level of 20 aphids/100 compound leaves. Potato seed produced in the plains using this technique gives better plant stand and yield in all the potato growing regions because of its better physiological age for quick emergence and faster growth of haulms. Thus, the seed produced in the north-western plains and kept in cold stores during April-September is most useful for planting in the plains in October, particularly when early crops are to be raised. After it is removed from the cold store, the seed should be carefully sorted and dried by spreading on the floor. This post-cold-storage treatment is necessary to get rid of the problems of sweating, rottage and brings about the respiratory equilibrium of tubers. 

Seed size and spacing: All sizes of seed tubers can be utilized as seed but medium-size tubers (25-55 mm or 25-75 g) are often better than other grades. Even in seed size, tubers of 35-40 mm or 45-50 g are ideal. Comparable yields can be obtained by planting medium-size tubers at 60 cm x 20 cm spacing and large-size tubers at 60 cm x 25 cm spacing keeping the plant populations at 83,000 and 67,000 plants/ ha, respectively. For small-size seed (25-35 mm), a population of 111,000 plants/ha (60 cm x 15 cm inter and intra-row spacing) is ideal. The optimum seed rate for getting a high yield is 2.5-3.0 tonnes/ha.

The use of large-size tubers increases the seed rate. Therefore, in some areas the big tubers are cut into 2-4 pieces before planting However, it is advisable to use medium-size whole seed tubers, because several saprophytic organisms often establish on the cut surface of the tubers causing seed piece decay leading to poor and gappy germination. In the plateau region, which depends on seed potatoes from north Indian hills, the large tubers are generally cut and planted late in November. For spring crops in north-western plains, for which the seeds are procured from the hills, the cut potatoes are used as seed. The seed tubers are cut about a week or 10 days before planting and treated with fungicides (dipped for 10 min in 0.2% solutions of Mancozeb) and spread at a cool and covered with moist hessian cloth so that the cut surface suberizes and seed pieces do not rot.

Pre-sprouting of seeds:Pre-sprouting of tubers before planting ensures multiple, stout, and healthy sprouts which help in quick emergence and uniform stand of the crop. It also increases the number of shoots per plant and leads to a larger proportion of seed-size tubers. For pre-sprouting, the tubers are kept in shade in diffused light in baskets or trays or spread in a thin layer on the floor. Seed stocks are examined twice a week to remove rotten tubers. Cold stored seed tubers are generally dormant, give low yields if planted immediately. One week pre-sprouting period is sufficient for all sizes of tubers in north-western plains and of 3 weeks in eastern plains.

Breeder’s seed production:Production of breeders’ seed and its supply to the state/central seed producing agencies is an important national mandate of ICAR CPRI. This program is being undertaken at 5 regional stations: Kufri (Himachal Pradesh) in the hills and in Indo-Gangetic plains at Jalandhar (Punjab), Modipuram (Uttar Pradesh), Gwalior (Madhya Pradesh), and Patna (Bihar) with targeted production of 25,200 q. To achieve the targeted production, a scientific approach is being followed starting with tuber indexing, field multiplication in stage-I, stage-II, stage- III, and stage IV.

Tuber indexing: Yearly about 32,000 tubers are indexed at Modipuram (12,000), Gwalior (10,000), Jalandhar (4,000), Patna (2,000), and Kufri (4,000), out of which about 26-27 thousand tubers are tested by ELISA during indexing against all common viruses (PVX, PVS, PVA, PVY, PVM and PLRV). In total 19 commercial varieties are covered in the tuber indexing program.

Stage I multiplication: The healthy indexed tubers are planted in stage-I individually at a wider spacing of 1 x 1 m and tested individually by ELISA against 5 potato viruses and also inspected visually for mosaics and other abnormalities/ varietal mixture. The produce of only healthy plants is planted in the next stage.

Stage-II multiplication (clonal multiplication): The healthy produce of a single hill in stage-I is planted in a row as a clone. The crop in stage-II is again tested against viruses and inspected for visual mosaics. The healthy produce of stage-II is bulked variety-wise and planted in the next stage.

Stage-III multiplication (bulk multiplication): The variety-wise bulked produce of stage-II is planted in stage-III for bulk multiplication. The crop here is randomly check tested against contagious viruses (PVX and PVS) and the whole crop is visually inspected for mosaics. The healthy produce is bulked for multiplication in the next stage to produce breeders’ seed

Stage-IV multiplication, Breeders’ seed production: The healthy produce of stage-III is planted in stage-IV to produce Breeders’ seed. This crop is also check tested and visually inspected for disease freedom. The plants showing any symptoms of the virus in testing or mosaics/ varietal mixture in visual inspection in all the stages are rouged out. A total of 27,755 q breeder seed (stage I-IV) was produced during 2003-04 against the targeted production of 25,200q.

Micropropagation: Keeping in view the cumbersome method of maintaining the stocks free from viruses and diseases the new technology of tissue culture, micropropagation production of microtubers and microplants, etc. was introduced to supplement the availability of virus-free seed stocks in the breeders’ seed production program. Potato: readily responds to the totipotent nature of plants. tissues for micropropagation that facilitated risk-free export/import of disease-free planting material in tissue culture. The process typically consists of: (i) production of virus-free potato plants using meristem culture, (ii) micropropagation of virus-free plants, (iii) production of micro-and/or mini-tubers from micropropagated plants, and (iv) growing healthy seed crops using minitubers as planting material. Seed production through the hi-tech system has three different sub-systems, viz. (i) microplant based seed production system, (ii) microtuber based seed production system and, (iii) aeroponic based seed production system. Under hi-tech seed production system, nucleus planting material is produced in the laboratory under controlled aseptic conditions. The virus-free plants. are used as mother plants for micropropagation. The microplants/microtubers are planted in net-house conditions for the production of mini-tubers (G-0). The minitubers produced in Generation-0 are multiplied in Generation-I at a spacing of 60 cm x 15 cm. The produce of Generation-I is further multiplied in generation II. The produce of Generation-II is called Breeders’ Seed. Aeroponics is the process of growing plants in an air mist environment without the use of soil or an aggregate medium. There is a tremendous scope to increase healthy seed production vertically by adopting aeroponic technology of seed system where the increase in multiplication rate up to 1:50 can be achieved. The aeroponic seed production system has very high productivity. It prevents exposure to unfavorable soil conditions and the minitubers harvested from this system are free from all soil-borne pathogens. The desired size of minitubers can be harvested sequentially and this could reduce the cost of minituber production. 

For the elimination of viruses each year 300-400 apical domes of different varieties are excised and inoculated on MS medium. The explants are indexed/tested by ELISA and ISEM and healthy plants are sub-cultured 8-10 times to get the desired number of healthy plants/ microtubers required in each variety. About 45,000 microtubers and 10,000 microplants are produced annually for direct planting in net houses in the plains and more infrastructure is being created in the new Seed Technology Laboratory to augment the production of more microtubers/microplants. These microtubers/ microplant yield about 175,000 to 180,000 minitubers and they are planted in fields next year in Generation-1. The produce of Generation-I is planted in Generation-2. The produce of Generation-2 is supplied to the state Agri/ Horticulture Department as breeder seed. Though this program covers only 10% area of breeders’ seed program, if one more field exposure is done at CPRI this percent can increase to 35-40% in near future.

True potato seed: The non-availability of good quality seed tubers, high seed cost, virus infiltration in seed tubers causing degeneration of seed stocks, and problems of long-distance transportation of seed from producing areas have led to the development of true potato seed (TPS) technology. This technology envisages the use of botanical seed or TPS for potato production. It has gained significance because unlike seed tubers, the TPS can be produced in all parts of the country by providing extra light for 4-5 hr depending upon climatic conditions. It can be easily stored over long periods of time. Disease transmission through botanical seed is negligible and it provides cheap planting material. About 100-120 g TPS is enough to raise a transplanted seeding crop. If the commercial crop is to be raised using seeding tubers, the nursery bed produce of 40-50 g TPS is enough to plant a 1 ha crop next year. Crop raised from TPS also provides better disease resistance because of high heterogeneity in the population.

A ware potato crop using TPS can be raised either through a transplanting of seedlings in the field or by using seeding tubers as planting material. In the first method, the seed is sown in nursery beds as practiced for seedling production of other vegetable crops. Potato seedlings at the 4-5 leaf stage are transplanted in the field to raise the crop. This method of raising a ware crop has been successful in Bihar, Gujarat, the plateau region of Madhya Pradesh, and Tripura where adverse temperatures do not limit the crop growth. In Punjab, Haryana, and western Uttar Pradesh, this method is not very successful owing to high temperatures in September and low temperatures from November, which restrict the crop grown resulting in poor yield. In the second method, the seedlings in nursery beds are allowed to grow till maturity to produce seedling tubers. These seedling tubers are used as seeds for raising the commercial crop next year. The crop production using seedling tubers is successful in all potato-growing regions of the country. The crop yields are also higher with seedling tubers. This technology is becoming popular in Bihar, Karnataka, and Tripura. The ICAR-Central Potato Research Institute, Shimla, has developed and recommended a relatively uniform and high-yielding TPS population of 92-PT-27 for commercial cultivation in the country.

Cultivation

Planting

Potato has wide adaptability for planting and harvesting in different agro-climatic zones In the north-western Himalayas, it is planted in May/June in valleys and during April in high hills (2,500-3,000 msl), as spring crop during January/February and as an autumn crop in August/September in the mid-hills (1,000-1,800 msl). In north-eastern hills, potato is planted in March in the high hills. In valleys and lower hills, there are 2 potato-growing seasons with plantings in January/ February and August/September. In Nilgiri hills, 3 potato crops are raised almost in succession, their planting times are April, August, and January.

In Punjab and western Uttar Pradesh, early potato crop is planted during 10-20 September, in central Uttar Pradesh the first week of October, and in Bihar between the second and third week of October. The crop is usually harvested after 60-70 days to take advantage of the high prices of fresh potatoes. Mulching of early potato crops with paddy straw, paddy husk, maize stalks, and dhaincha stalks is beneficial for getting high yields. The main crop in Gangetic plains is planted during October-November. The potato season first starts in the north-western plains and culminates in the northeastern plains. Planting of late or spring crops in December/January is confined to some parts of northwestern plains only. In plateau regions of peninsular India, where summer temperatures are somewhat mild, 2 crops, one in winter and the other in summer are raised.

For hot weather cultivation, the fields are ploughed during summer in May and June to reduce the incidence of soil-borne disease and control perennial weeds. Green manure crops like dhaincha and sanali may be sown before the onset of the monsoon. The green manure crop is buried in the soil after 7-8 weeks. This practice reduces the N, P, and K requirement of the crop by 20-30% and improves potato yields up to 3 tonnes/ha.

If green manuring of the fields is not possible, farmyard manure @15-20 tonnes/ha incorporated and ploughed in the field before planting may be After deep ploughing and good pulverization of the soil, when the seedbed is ready, tubers are planted in lines. The first line is drawn straight with a rope and subsequent lines are marked at a distance of 60 cm from row to row with help of a marker. Half dose of N and a full dose of P₂O and K₂O is applied in furrows and mixed in the soil. Seeds are kept in the furrows at a distance of 20 cm from tuber-to-tuber and covered with soil using a ridger. The planting should preferably be done in the morning or in the evening to avoid heated soil covering during mid-day in plains. Tractor-drawn semi-automatic or automatic planters are also used for planting.

Manuring and fertilization

A mature potato crop yielding between 25-35 tonnes/ha needs about 120-150 kg N/ha. The peak period of N uptake varies from 40-70 days in plains and 65-85 days in hills. Nitrogen application increases the plant growth, leaf area, tuber number, and tuber size. The maximum N response is recorded in alluvial soils followed by hill soils, red soils, and black soils. Potato varieties differ among themselves in their N fertilizer needs. The long-duration varieties are more responsive to N fertilizers than the short-duration ones. N is applied in split doses. Half of the dose should be applied at the time of planting and the remaining half at the time of earthing up.

Phosphorus is the second limiting nutrient in potato production and its deficiency is more pronounced in acidic hill and red laterite soils. An average crop yielding 25 tonnes/ha needs about 45 kg P₂O₂/ ha. Phosphorus deficiency retards growth with leaves becoming dull dark green without luster. The application of 50-100 kg P₂O,/ha along with N is required in most of the soils. A full dose of P is applied at the time of planting.

The application of K along with N and P is required to get optimum yield. On average, the potato plant removes 150 kg K/ha from alluvial soils of the plains and 190 kg/ha from acidic brown hills soils. Response to K is the highest in alluvial soils, followed by hills. soils, red soils, and black cotton soils. The optimum K dose is 98 kg/ha for alluvial soils, 93 kg/ha for hills soil; 111 kg/ha for red soils, and 70 kg/ha for black soils. P deficiency retards plant growth and shortens internodes. Leaves become dark bluish-green in mild K deficiency and under severe deficiencies, terminal leaves show bronzing accompanied with necrotic spots.

The response to N, P, and K depends not only on the fertility status of the soil but also on variety, cropping system, and source of nutrients. The P and K applied to soil leave significant residues which reduce the fertilizer needs of the succeeding crop.

The potato crop in most parts of the country generally does not to the application of Zn, Cu, Mg, and Fe. Only a marginal increase in the yield of potato was observed with the application of Zn at Kalyani (West Bengal), Kanpur (Uttar Pradesh), and Palampur (Himachal Pradesh). Similar are the cases with Fe, at Kanpur and S at Hisar (Haryana), Faizabad (Uttar Pradesh), and Deesa (Gujarat).

Interculture 

Earthing-up is done when potato plants are about 8-10 cm tall. Final earthing-up in the plains is done 25-30 days after planting and in hills when the crop is about 6-8 week-old. The second half dose of N is applied at the time of the final earthing-up. Weeding is done as soon as weeds emerge in the crop. Application of pre-planting weedicides such as Fluchloralin (0.7-1.0 kg a.i./ha) and Pendimethalin (0.5 kg a.i./ha) is useful to control weeds in potato crop.

Irrigation

Potato tuber contains nearly 80% of water. Adequate and regular water supply is, therefore, needed for sustained growth of the crop and getting higher yields. Potato crop in high hills and plateau region in Kharif season is grown as rainfed, whereas, in the plains, it is grown under irrigated conditions. The quality of water used for irrigation is an important factor. Water with a high concentration of dissolved salts is undesirable for potatoes. First irrigation immediately after planting, particularly if the soil is relatively dry, is desirable for better emergence. Second irrigation may be given after 12-15 days when 2-5% germination has taken place. Subsequent irrigations may be given at 6-10 days intervals depending upon soil and water demand. Water stress reduces tuber yield and increases the proportion of small-size tubers. Mulching helps in getting higher yields in warmer regions of the country.

Water is one of the vital inputs in potato production and its optimum use is a major concern. Sprinkler and drip irrigation systems have been evaluated and compared with the standard furrow irrigation in Indian plains. The drip system is the most economical, giving the highest productivity, enhancing the quality of tubers, and saving about 50% water. The system also enables fertilizer economy by applying fertilizers through irrigation water. The sprinkler system is the second best. This system is beneficial on frosty nights as it reduces frost damage in potatoes. For the hills, several methods of water harvesting were developed. These are used to conserve snow meltwater and run-off water during rainy seasons to meet the water requirements during dry periods.

Physiological disorders

There are several disasters commonly referred to as non-parasitic, which are the result of physiological imbalances caused by unfavorable environmental conditions. These are discussed here.

Internal brown spot 

It is characterized by irregular, dry brown spots scattered through the flesh of tubers but not in the vascular region as in the case of brown rot. It is a very minor disorder that appears particularly in light sandy soils, which are not irrigated regularly. The affected tubers lose much of their value as table potatoes. It is not transmissible, however, planting of severely affected tubers should be avoided as they often produce weak plants. An old variety, Craigs Defiance, is prone to this disorder.

Black heart

If potato tubers are stored at a temperature of 35-40°C, they develop black heart in a few days. In a black heart the inner tuber tissues breakdown and become black. Lack of oxygen is the probable cause. It is also probable that at high storage temperature, accumulation of CO₂ at the center of the tuber might contribute to damage and to the subsequent decrease in respiration leading to the development of the black heart. This disorder is of minor importance as it appears only in ordinary over-heated and ill-ventilated farm stores. Therefore, avoid storage at temperatures above 35°C and poor ventilation.

Hollow heart

The hollow heart consists of an irregular cavity in the center of tubers. In tissue surrounding the cavity, there is no decay or discoloration. Hollow heart condition appears often in varieties that bulk rapidly and produce over-size tubers. In extra large-size tubers of Kufri Jyoti and Kufri Sindhuri hollow hearts may appear. This condition can be avoided by the closer spacing of plants and avoiding excessive use of fertilizers.

Chilling injury

Chilling injury may follow prolonged storage of tubers at a temperature of about 0°C. This results in the development of discolored blotches in the flesh of tubers, which vary from light reddish-brown to dark brown. This disorder completely inhibits the sprouting and the emergence of affected tubers when planted.

Freezing injury 

Freezing injury occurs due to ice formation in potato tubers when exposed to temperatures below 0°C. Tubers, which are only briefly frozen show a blue-black discontinuous ring in the vascular region. More severe injury leads to a blue-black necrotic network in the pith, in addition to necrosis in the vascular region. In tubers frozen for more than half an hour, the cut surface of the thawed tuber shows diffuse areas of black discoloration. If the tubers are frozen for about 4-5 hours they show no blotch or discoloration but on thawing the whole tuber becomes wet, soft, and liquid oozes out of it.

Diseases and pests

Bacterial diseases

Brown rot or bacterial wilt is the most important in the mid and lower hills as well as in the plateau areas. The affected plants first show drooping of the leave which turn pale green, wilt, and ultimately die. The disease is soil-borne carried through seed tubers. Common scab is another soil-borne tuber disease found in India. The symptoms appear as small round spots around the lenticels and several of them coalesce and form patches on the tuber surface. The scab decreases the market value of the produce. Soil factors like texture, moisture, temperature, and fertilizers influence the incidence of the disease. Fertilizers, which increase the soil pH, favor diseases while dry and warm soils also favor the development of the disease. Black leg and soft rot are the other bacterial diseases of localized importance in some pockets.

Viral diseases 

Viral diseases are important since they reduce the yield, which decreases with each successive generation of the seed and so it is called seed degeneration. There are many viral and mycoplasmal diseases affecting potato crops like leaf roll virus, purple top roll, marginal flavescence, witches broom, stem necrosis, mosaics, etc.

Fungal diseases

The fungal diseases that afflict potatoes are given here.

Late blight

The potato crop in the northeastern, northern, and southern hills of India faces a heavy attack of late blight. In the plains, it occurs less frequently but its damage could be very severe. Under favorable conditions, it spreads very fast making it one of the most dreaded diseases. With reports of sexual reproduction of Phytophthora in India, the risk of pathogen threat has become even more pronounced. It appears as small brown-purplish lesions of varying sizes on the foliage. The blight-affected leaves show, on the under surface, a whitish cottony growth all-around a faint purplish-black central lesion.

Early blight 

Though it occurs both in the hills and plains of India it is a major problem only in the Deccan plateau during the Kharif crop. The symptoms range from large spots, which later assume a blotchy appearance or small angular irregular spots. The disease first appears as small dots on the leaves, later these enlarge to dark brown necrotic spots with characteristic concentric rings.

Common scab

It is another soil-borne tuber disease found in India. The symptoms appear as small round spots around the lenticels several of which coalesce and form patches on the tuber surface. The scab decreases the market value of the produce. Soil factors like texture, moisture, temperature, and fertilizers influence the incidence of the disease. Fertilizers, which increase the soil pH, favor disease while dry and warm soils also favor the development of the disease.

Wart 

This disease is restricted to Darjeeling and the nearby hills of West Bengal. The spread of warts to other areas was checked by effective quarantine measures. The abnormal growth activity of the host tissue leads to wart formation. Severely infected tubers assume the form of a shapeless wart ss. In the Darjeeling hills planting of wart immune varieties like Kufri Jyoti and Kufri Kanchan are recommended.

Other fungal diseases 

These were the diseases that were once important or are now restricted to certain situations only-fusarium wilt, leaf blotch, stem canker, verticillium wilt, black scurf, etc.

Insect pests

The pests that afflict potatoes are described here.

Tuber moth (Pthorimaea operculella): Larvae of the insect make mines in tender leaves, petiole, and stem. They also mine into tubers and form dirty-looking silk-lined galleries. In stores, saprophytes grow in damaged tubers and rot sets in. About 30-70% damage of tubers in storage and 0-45% tuber damage in fields have been reported. It is a major field and country store pest in the plateau region.

Aphids: Aphids suck the sap from potato foliage causing leaves to curl downwards. The leaves become yellow and die. Myzus persicae and Aphis gossypi are efficient vectors of potato virus (es). Major damage is through the transmission of viruses.

White flies (Bemisia tabaci):Whiteflies are tiny, soft-bodied, winged insects. They are active and thrive year-round in the south but go dormant during the winter in northern states. Whiteflies can seriously injure plants by sucking sap causing wilting, stunting, or even death of the young plants. Adults can also transmit several viruses. The most economically important whitefly transmitted viruses are gemini viruses.

Cut worms (Agrotis segetum and A. ipsilon): The larvae damage the crop at the initial stages by cutting young plants at ground level. They also feed on shoots resulting in stunted plant growth. After tuberization, they feed on potato tubers by boring and nibbling into tubers. About 40% of plants are damaged by this pest.

White grub (Lachnosterna longipennis/Lachnosterna coracea): Two species, viz. Lachnosterna longipennis and L. coracea are predominant and damage potato crops in the hills of Uttrakhand, Himachal Pradesh, Jammu and Kashmir, and Northeastern hills. White grubs feed on potato tubers. Losses range from 10-75%, which may be even higher if harvesting is delayed much.

Leafhoppers: Leafhoppers (also known as jassids) suck plant sap and may cause direct damage to the crop. Among the hopper species, Alebroides nigroscutulatus and Seriana equata are reported as the vectors for yellows diseases, viz. Purple Top Roll (PTR) and Marginal Flavescence (MF) in potato. Other species of leafhoppers (Empoasca devastans, Balclutta hebe and Amrasca biguttula) cause direct damage to potato crops as their nymphs and adults suck sap from potato plants and cause hopper burns.

Thrips (Thrips palmi): High temperatures and dry weather during September/October are favorable for thrips. Under these optimum conditions, many thrips species can explode in population. Thrips palmi is the most predominant species in India. During winters many thrips species hibernate either as pupae or adults in the underground litter. In addition to feeding on foliage, thrips also spread plant diseases through the transmission of tospoviruses. Thrips acquire the virus only as nymphs but retain and transmit it throughout their life. Thrips palmi is the predominant species and probably the most efficient vector of tospoviruses. In India, potato stem necrosis disease (PSND) is spread by this vector.

Mites (Hemitarsonemus latus): The damage starts from the apex leaf and goes downward. The leaves roll inward, showing oily spots on upper surfaces. The lower surface gets a sooty appearance. The leaves ultimately become bronze in color and wither. The plants become stunted and finally die. A heavy mite infestation might cause a 50% loss in yield. It is a major pest in the Deccan plateau.

Nematodes: Both root knot nematode (Melidogyne incognita) and cyst nematodes (Globodera pallida, G. rostochinensis) occur in India. Cyst nematode is serious but is restricted to Nilgiri hills. Symptoms include loss in the vigor of plants, similar to a mineral deficiency. The disease appears in patches. The underground symptoms include the presence of galls/cysts on roots and pimple-like structures on tubers.

Cultural management of Diseases and Pest in Potato 

Viral diseases: The diseases can be managed through the use of healthy seed tubers, produced/multiplied under vector-free or low vector pressure period of which occurs in high hills during summer and in the Indo Gangetic plains during autumn/early winter. Disease-free stocks, in the beginning, are selected through indexing of tubers and subsequently through field inspections and rouging of diseased/suspected plants. When healthy stocks are not found, they are freed from viruses through mericloning followed by testing for viruses.

Fungal diseases:Management of important fungal diseases are discussed below.

Late Blight: Plains-Plant resistant-varieties like Kufri Jyoti, Kufri Badshah, Kufri Chipsona, Kufri Sindhuri, Kufri Jawahar, Kufri Sutlej, etc. Check seed tubers thoroughly before planting and cull out infected tubers. Make high ridges to prevent exposure of daughter tubers. When the temperatures are favorable for late blight stop/give light irrigation.

Hills-grow suitable resistant variety depending upon the location like Kufri Jyoti, Kufri Giriraj, Kufri Megha, Kufri Kanchan, and Kufri Swarna. Plant disease-free seed. Remove ground keepers/bolters as early as possible.

Early Blight: Follow optimum cultural practices to keep the crop vigorous. Mancozeb 0.2% controls early blight also. Avoid solanaceous crops in nearby fields. Common scab: Practice hot weather cultivation. Use disease-free seed tubers. Use seed treated with 3% boric acid. Irrigate the crop frequently to keep the soil near field capacity especially at the time of tuber initiation. Grow crops like wheat, pea, oats, barley, lupin, soybean, sorghum, bajra, and green manuring in rotation.

Wart: Practice long rotations. Grow immune varieties like Kufri Jyoti, Kufri Sherpa, and Kufri Kanchan. Use disease-free seed. Rogue out infected plants and burn warty tubers to destroy them. Practice sanitation and avoid throwing warty lumps and peelings in the manure pit but burn them.

Bacterial wilt: Use only disease-free seeds. Do not cut seed tubers. Apply stable bleaching powder (12 kg/ha) along with fertilizers. Follow 2-3 years rotation with crops like maize, finger millet, cereals, garlic, lupin, onion, cabbage, and sunhemp. Follow minimum. tillage after emergence and keep the fields weed-free to minimize the chances of the survival of the pathogen.

Insects pests: Cultural methods for control of important insect pests are given below.

Tuber moth: Use unifested seed. Remove leftover tubers, volunteer potatoes. Practice deep planting and prevent exposure of daughter tubers due to cracking of the ridges by giving frequent light irrigations.

Cut worms: Hot weather cultivation. Fire accompanied with light during the night. Cutworm moths get attracted to light and fall in the fire.

White grub: Hot weather cultivation. Shaking shrubs around the field to down beetles and killing them by spraying suitable spray.

Mites: Spray foliage with wettable sulphur.

Root knot nematode: Practice hot weather cultivation. Avoid infested seed tubers. Follow minimum two-year crop rotation like maize-wheat-potato-wheat.

Cyst nematode: Practice crop rotation with crops like radish, garlic, beetroot, turnip so that potato comes after 3-4 other crops.

Harvesting and post-harvest management

Potato tubers are harvested as soon as they mature. In loamy or heavy soils, tubers should not be allowed to remain in wet soil after maturity because the lenticels on their surface may proliferate. There is less consumer acceptance for such tubers. It is never advisable to harvest the tubers in wetland. If the tubers are to be stored for some time before marketing or are to be cold stored it is better to cut haulms and not to irrigate the field 10-15 days before harvesting. This ensures tuber skin maturity and dryness in the soil. The late sown crop in plains should be harvested latest by the April-end to avoid high temperatures and charcoal-rot infection in tubers.

After harvesting, tubers should be surface dried and kept in shade in heaps for 10-15 days. All rotted and damaged tubers should be periodically removed. The produce should be graded on the basis of tuber size and packed in gunny bags for marketing.

If the product is to be marketed early to take advantage of the high market price, it is advisable to harvest potatoes in stages. This is because of the highly perishable nature of the immature tuber. Fresh potato has delicate skin, which gets bruised easily and extensively providing invasion sites to rot-causing organisms. Also, bruising initiates an oxidization process, which subsequently imparts dark color to the exposed surface of tubers reducing its market value.

Mechanization: Potato is an input-intensive crop and proper mechanization helps inefficient management of inputs and improves the timeliness of operations and quality of work. Potato has been grown in India for centuries using hand tools and animal-drawn implements. However, modern practices of potato production demand precise placement and utilization of costlier inputs like seed, fertilizer, pesticides, etc. Mechanization has played important role in the timeliness of farm operations, reduction of drudgery as well as cutting down labor costs. A number of tractor/animal-drawn equipment have been developed in India. These are fertilizer applicator-cum-line marker, potato planter, culti-ridger, inter-cultivator, pesticide applicator/sprayer, haulm cutter, potato digger, potato grader, solar dehydrator, etc. Some of this equipment is commercially available in India.

Processing: In developing countries like India, potato is primarily used as a vegetable for human consumption. In India about 0.05% of total potato production is exported, 7.5% processed, 10% used as seed, 12% as waste, and the remaining about 70% is consumed as a fresh vegetable.

Home scale processing of potato into chips and lachha is a common practice in potato growing areas. Perhaps the first attempt at processing potatoes in India on a commercial scale was made by Col. Rennick in 1911, who established a factory at Narkanda in Himachal Pradesh to produce potato meals. But there was no visible progress in potato processing under organized sector in the country for a long time. However, owing to increased potato production, incentives of the Government of India, increase in per capita income, and demand for processed potato products, there had been visible growth of potato processing in the country during the last two decades. Now about 7.5% of potatoes in the country are processed into main chips, French fries, flakes, and dehydrated products.