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Rice Production and Protection

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RICE PRODUCTION AND PROTECTION

PRODUCTION

Rice , which is known as Oryza sativa in Latin is one of three principal food crops in the world .It is consumed as staple food by more than 2700million people around the world. The overall production of rice globally is estimated to be around 575 million tonnes and the average productivity is about 3.83 tonnes/ha. In India rice accounts for close to 40% of foodgrain production and is grown on 44.8million ha and its cultivation provides gainful occupation and livelihood to about 70% of people in rural areas. Total production is estimated in the region of 125 million tones.

Rice cultivation in India is confined to four ecosystems which are as follows.

  • Irrigated
  • Rainfed Upland
  • Rainfed Lowland
  • Flood prone

Rice crop is extremely versatile and adaptive and as far as India is concerned it can be grown in most agro climatic zones and soil varieties. Rice can be grown at altitudes ranging from sea level to 3000metres. Heat and Humidity is a prerequisite for the rice plant The average temperature range throughout the crop cycle is between 21 to 37 degrees centigrade. Temperature, rainfall , humidity and other climatic conditions affect the plant. Rice is grown in all types of soils. Since rice cultivation requires  large amounts of water and moisture ,those soils which have water retention capabilities for long periods are ideal. Clay and loam soils suit growth of rice. The following soil types are most suitable for rice cultivation.

  • Alluvial soil
  • Black soil
  • Red soil
  • Lateritic soil

Rice is chiefly grown in the Kharif and Rabi season though there are parts of the country where it is grown in three or even four seasons. Harvesting of rice is generally undertaken upon the maturity of the grains. The paddy grains should consist of at least 20% moisture at harvest time. Harvested paddy is dried under shade to reduce the moisture content to about 14% which is the required limit for storing and milling.

Post harvest the the problem is one of marketing the rice produced. Buyers and Sellers together create a market. Being a staple commodity the demand for rice comes from millions of consumers. In rural areas producers are also consumers and and about 57% of the production is consumed  locally  by the farmers and the rest is marketed.

PROTECTION:   

Diseases and Pests take a heavy toll on the Rice crop every year. We can use the following classification  of diseases and pests to understand the above.

  • Insect Pests
  • Nematode Problems
  • Fungal disease
  • Bacterial disease
  • Viral disease

Insects Pests:

Rice in India is grown in different agro-climatic zones and ecosystems. Insect pests vary according to the conditions. Insect pests are more prone to irrigated areas. Another endemic factor is the use of nitrogenous fertilizers. There are about 100 species of insect species which attack rice crops out of which about 10 are considered common.

1.Stem borer      4.   Leafhoppers           7. Rice bug                  

2. Gall midge        5. Whorl maggot        8. Rice caseworm  

3. Plant hopper    6. Cutworm                  9. Rice hispa

Nematode Problems: 

A nematode parasite affects rice plants in most agro ecological systems The losses caused due to nematodes are often difficult to investigate. These problems are often ignored by the farmers due to their unstable economic conditions. It is imperative to develop resistant varieties  to reduce the incidence. Apart from causing direct damage nematodes often expose plants to disease causing pathogens thereby increasing the risk of disease infection. The average losses caused by the nematode pest is more in the developing countries than the developed ones.

Fungal Diseases :

Fungal pathogens cause a number of diseases. They are about a dozen in number and their etiology has to be understood in order to manage the consequences. The following fungal diseases are worth mentioning:

1.Blast                             4.Foot Rot            7. False Smut

2. Sheath Blight             5. Sheath rot        8. Bunt/kernel smut

3. Brown spot                6. Stem rot            9. Udbatta

Integrated Disease management is the best way to control the abovementioned diseases. The concern is to maintain the health of the crops. Chemical control generally dominates the IDM. Crop health surveillance is a good strategy within the IDM system. It involves a thorough monitoring system to check prevalence and severity of disease. It may be a one time activity or a regular periodical activity. Surveillance activity also help in identifying potential disease pretty early on so that corrective action may be taken. 

Bacterial Disease:

The etiology or the causes of bacterial disease are multifarious  ranging from heavy use of nitrogenous fertilizers, uneven sowing and planting, high plant population per unit area. Although there are nine types of bacterial diseases the two most common ones are Bacterial Blight and Bacterial Leaf Streak.  Bacterial blight was first observed in the coastal region of Maharashtra around the year 1951 . now the disease has spread throughout India. Within the country the losses have been huge , the quantum of loss generally depends on the stage of infection and the severity of it. The losses could range from 6 to 60%  as far as grain yield is concerned. The loss is always  greater when the disease strikes during the pre-emergence stage rather than the flowering and milk stages. The following management practices are generally recommended to ensure the minimization of the risk of incidence of bacterial blight disease

  • Tolerant cultivars should be grown widely
  • Seedlings must be raised from a disease free crop and infected seeds must be treated with antibiotics.
  • Susceptible collateral hosts around rice fields have to be eradicated.
  • Pruning of leaves either at the time of transplanting or afterwards must be avoided.
  • Water logging wherever possible should be avoided.
  • Field to field irrigation should be avoided and each field should be irrigated through a separate channel.
  • Moderate levels of nitrogen and required levels of potassium have to be used.

Viral Diseases of Rice

There are roughly 21 known viral diseases of rice which occur around the world. Historically , it was Japan where a viral infection was recorded as far back as 1897. It has been noted that 1965 onwards viral diseases like tungro, grassy stunt and ragged stunt have occurred mostly in South and South-East Asia. Rice viruses are generally transmitted by insect vectors. Insects such as leafhoppers, planthoppers, aphids and beetles play a large part in transmission of virus. Out of close to thirteen viruses, about ten occur in Asia and the remaining three in Europe. The three most widespread diseases need to be briefly discussed.

Tungro Disease :

It has originated in the Philippines and is known since 1940 by various names. This disease is widespread and causes serious losses in production. It has been widely reported from Indonesia, Bangladesh, Thailand , India and Malaysia.

Typical symptoms are the yellowing of leaves and severe stunting of the plant. Tungro is a composite disease caused by the combination of two distinct viruses either individually or jointly. They are the Bacciliform  and Spheroid. The tungro virus is generally transmitted by the leafhopper vector. There is no transmission either through the seed or through sap inoculation.  

Grassy Stunt Virus:

The incidence of this virus is presently very low in India, hence its management aspects have been neglected. It was discovered in Philippines in 1962. The countries where this virus is prevalent is Ceylon, Indonesia, Thailand , Malaysia and JapanThe symptoms are quite similar to what happens in Tungro, the stunting of the plant and the paling and yellowing of leaves. In addition short , erect and pale leaves start appearing. The transmission through an insect vector such as the brown plant-hopper. Rice is the main host for this virus but infection can take place, in other words it can be transmitted to 16 oryza spp and 5 weed hosts.

Ragged Stunt Virus :

It was discovered in 1976 mainly in Indonesia and Philippines Of late the incidence of this disease has been quite low and controlled but has a tendency to appear sporadically in localized areas wherever the vector insect and the virus are present. Plants affected with this virus display symptoms of stunted growth, twisting and ragging of leaves with swollen veins. Panicle emergence is late in the infected plants. It is transmitted by different species of brown plant-hopper but not through the eggs The incubation period is quite long varying from four to thirty three days. The insect is capable of long flight.  Apart from rice it can infect 17 other graminaceous hosts.

Control of Rice Viral Disease :

Conventional methods may not be able to control viral pathogens. Comprehensive and an integrated approach is needed. Resistant varieties, cultural control and chemical methods are used to control the virus. Time of transplanting, adjustment of  planting time in low vector population period and use of insecticides are other methods of prevention of disease.

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Please note that this is the opinion of the author and is Not Certified by ICAR or any of its authorised agents.