The rats can be brought under two different groups as domestic rats and field rats.

Domestic rats

These are found near human dwellings.

1. House rats (Rattus rattus): There are two subspecies; one with white belly and the other with grey belly. Tail length is more than the length of head and body. They are found in houses and eat anything that man eats. They also cause qualitative damage due to deposits of faecal matter, urine and hairs. It damages gunny bags, plastic containers, clothes, electric wires etc. These house rats in the fields damage tender coconuts and cocoa pods. They also act as carriers of several human and animal diseases.

2. House mouse (Mus musculus): Fur is short without spines. Tail is almost naked and larger than head and body. The mouse is very active and is found in houses and gardens. It can climb up walls. It damages clothes, plastic containers and food materials.

3. Large bandicoot rat (Bandicota indica): This is the largest domestic rat. Fur is coarse. Tail length is almost equal to the body length. Body weight ranges from 750 to 1000 g. It damages all tuber crops. It also damages concrete buildings by making burrows under the basement.

Field rats
1. Large bandicoot rat (B. indica): Large bandicoot rats are also seen in the field. So this can be considered both as domestic and field rat.

2. Lesser bandicoot rat (B. bengalensis): It is a short tailed mole rat. Tail length is only 70% of the body length. Fur is short and coarse. It is seen making burrows in the paddy field bunds and also in areas where crops like tubers, vegetables, coconut and young rubber are cultivated.

3. Field mouse (Mus booduga): Fur is short and coarse and is mostly found in gardens and fields. They make small burrows for living. Tail is slender and nearly naked. Tail length is shorter than body and head. The burrows of this species are found in the paddy fields. They are found feeding on paddy grains in the mature crop as well as seeds sown in the nursery.

4. White rat (Tatera indica): More than one rat per burrow is common in this species. The tail is longer than the body and is provided with a terminal tuft of long hairs. The eyes are large. Tail is double coloured.

5. Long tailed tree mouse (Vandeleuria oleracea): The fur is soft and tail is much longer than the body. They are found in most parts of India inhabiting trees and shrubs. They damage the inflorescence of arecanut and leafy vegetables by cutting its leaves.

6. Norway rat (Rattus norvegicus): These rats are found in waterlogged areas. This is a medium sized rat with tail more or less equal to the length of the head and body. These rats damage paddy crop. It cuts the plants at the base and chews the cut portion. Maximum attack is at the booting stage. The attack ceases after initiation of flowering. The damage is usually observed in patches away from the field bunds.

7. Soft furred field rat (Millardia meltada): These rats are found in cultivated field in pairs or small groups of 5 or 6. They are soft furred without spines. These rats cut the rice plants in the transplanted crop. The damage starts at the time of planting and continues up to harvest. The tillers are cut at the water level.

8. Bush rat (Golunda elliotti): These rats are seen in places near forest area. They live under bushes in nests. These rats are destructive to coffee plants. They feed on their buds and flowers. They damage paddy by cutting the plants in dryland paddy areas.

Integrated control of field rats
Rats cause considerable damage to agricultural practices and other human possessions in addition to acting as carriers of several human and animal diseases. Diseases like bubonic plague and weils disease (due to contamination of food by the urine of rats) are caused by rats. It is necessary that the importance of rat control be understood by all. An integrated approach to control rats involves the joint utilisation of all feasible control measures in a complementary manner to maintain the rat population at a very low level. Integrated control of field rats involves the following: (a) preventing their entry into a region or a building by putting up mechanical barriers or treating with repellents; (b) encouraging predators such as snakes, cats, dogs, mongooses etc.; (c) causing death by a variety of methods.

Methods of control

Environmental control
In this method of control rats are rendered to a hostile environment in which they cannot survive. The mud walls in villages may be replaced by thorny hedges thereby preventing the rats from making burrows. Good house keeping is regarded as the most economical and effective way of reducing rat population. Proper sanitation should be maintained by keeping food material inaccessible to rats in rat proof containers. The heap of garbage and sweepings in streets and towns should not be kept for a long period. Designing rat proof godowns and other buildings is another step to ensure environmental control.

Poisoning
Three types of poisoning are usually employed to control rats.

1. Acute poisons are those that can kill rats with a single dose; e.g. zinc phosphide.

2. Multiple dose or chronic poisons require repeated ingestion over several successive days; e.g. anticoagulants like warfarin.

3. Fumigants are gases and are usually pumped or released from pellets or tablets put in through burrow entrances; e.g. aluminium phosphide.

Acute poisons
Of the effective acute poisons used as solids, zinc phosphide is widely available. It is a dark grey powder and its toxic action is due to release of phosphine gas. When it is ingested, phosphine is released causing injury to the kidneys, liver and lungs followed by death after a few hours. In dry conditions zinc phosphide remains effective for 3 weeks. But in moist conditions there is faster deterioration. The dosage is 2%.

Zinc phosphide
This is used as a rat poison. Pre-baiting for 3-4 days in sequence is necessary to overcome the bait shyness. For pre-baiting and baiting, the same carrier material has to be used. Crushed wheat, maize, bajra, puffed rice, popcorn or rice mixed with a little jaggery and oil are excellent carriers. To prepare the carrier, 95 parts by weight of cereal ingredient is to be mixed with 5 parts of jaggery.

For baiting, zinc phosphide is mixed with groundnut oil and carrier in the ratio 2:2:96 by weight. At each bait station, 30-40 g of the bait mixture will have to be exposed. The stations may be selected in areas where rats are frequent, such as areas around kitchen, store and in homesteads. Expose baits in the evening and collect them in the following morning. Conduct baiting for three successive days.

Chronic poisons / anticoagulants
They interfere with the mechanism of blood clotting. Even in the absence of external wounding, animals, which have ingested them, develop internal bleeding and die from this cause. The anticoagulants are not very dangerous to men and domestic animals; e.g. warfarin, rodfarin etc. Pre-bating is not essential for anticoagulants.

For preparing the poison bait, mix 90 g of bait carrier with 3 g of jaggery and 2 g groundnut oil. After mixing these ingredients (95g), add 5 g of 0.5% concentrate of warfarin. Expose 25 g of poison bait in each station and collect the leftover materials in the early morning hours. These can be re-exposed in the evenings. Continue for 3-4 days in succession.

The liquid bait is prepared by dissolving 25 g of water-soluble anticoagulant (0.5%) poison in 500 ml of water. In each station, place 150 ml of liquid bait in shallow containers.

Warfarin blocks

Ingredients required: Warfarin 5 parts; broken rice 63 parts; jaggery 2 parts; paraffin wax 30 parts.

Mix broken wheat, jaggery and warfarin in the above proportion in a vial. Pour molten waxes into this mixture and mix thoroughly. Transfer this hot mixture immediately into a metallic tray of 2.5 cm depth. Spread evenly and press well with a spatula. Allow it to cool for sometime (about 20 minutes) and cut it into 5 x 2.5, 12.5 x 25 cm blocks with the help of a sharp knife. Keep it overnight. Next day remove the blocks from the tray one by one. The block is now ready for baiting.

Fumigants
Fumigants have been quite widely used against rodents. The most effective fumigant is aluminium phosphide, which is available both as tablets and pellets. Aluminium phosphide on contact with ambient moisture produces toxic vapour of phosphine. The tablets or pellets are to be introduced through openings of the live burrows, which are closed immediately thereafter.

Repellents
Chemical repellents include malathion and cyclohexamide which are repellents to house rats.

Biological control
Both field and domestic rats are subjected to attack by range of predators, parasites and pathogens. The predators include cats, dogs, snakes, owls, mongooses etc. The practice of rearing cats in house has been found to adversely affect rat population. The utilization of bacterial and viral infections has not proved successful in any part of the world.

Trapping
Trapping is the oldest method of controlling rodents. Almost any trap will catch some rats, but the response varies with different species. The rats are easily caught in cage or box, but a rat trapped in such trap will be exposed to other rats. So the rats develop trap shyness and they avoid such type of traps. The most effective rat taps are those, which can completely conceal the rats trapped in it; e.g. Moncompu trap. The rat traps can be grouped into a few categories.

Live traps (cage or box trap)

1. Automatic traps: These have counter balanced entrances. When an animal enters this type of traps, its weight makes it fall into a cage below. The counter balance on the trap door brings it back into place, leaving the rodent in the cage. These are intended to catch more than one rat; e.g. wonder trap.

2. Remote triggered trap: These work by upsetting a delicate balance when the bait stick is disturbed or when the weight is put on a treadle. Common type of this is the box or cage trap that captures one rat at a setting. A box trap is a wooden or metal box open at one or both ends, having one or two doors. Some have one or both will have overhead trigger on which bait is fastened and the door is released when the rat works on the bait. Others have a treadle in the floor on which the rat steps to drop the door.

3. Glues: A form of trapping in which a sticky substance entangles the animal

4. Pot traps: These traps are extensively used for catching rice field rats. This trap consists of a wooden plank, a mud pot of 10 inch diameter, a metal strip which carry bait and a 'Y'shaped wooden peg to which needle is tied; e.g. Moncompu trap.

The trap is to be set up in rice fields, after placing the base plank above the canopy level on a specially erected platform, on poles. The rats attracted by the bait climb over to the base plank and try to snatch off the bait tied on to the metallic strip. Slight disturbance of the strip dislocates the wooden needle from the strip slot and causes the pot to fall down abruptly over the rat. The pot and the plank are tightly held and removed in that position and immersed in water after inversion for killing the trapped rat. Since the live rat does not see the captured ones, they do not develop shyness against this type of mechanical trap.

5. Snap traps: Most of the rat traps fall within this category and are widely used for trapping rats. These kill the rat instantly by snapping, when the rat nibbles the bait placed in the middle of the open trap. These are variously called as "break back traps', "guillotine", "spring traps", "saw toothed traps" and "bamboo traps" depending upon the materials used in making them.

6. Kerosene tin trap: It is made by cutting the top of the tin and filling it with water up to 15 cm from the top. Chaff is floated on the water surface so that the rat cannot see water. Attractive and strong smelling bait like dry fish, fried coconut etc. is pinned on to a piece of cork or lightwood and floated on the chaff. A plank is leaned against the side to enable the rat to climb to the top. Seeing no water and eager to get the bait the rat jumps on to the chaff and gets drowned.

Success or failure of trapping is dependent up on the following factors.

a. Placement: Traps must be placed where animals will regularly encounter them than places out of their normal activity.
b. Concealment: It is not advisable to use new shining traps against rats. To overcome trap shyness it may sometimes be necessary to cover the trap with a slight coating of paper or dry leaves that does not interfere with the trigger or action.
c. Size and design: Traps should be neither too small nor too large for the anticipated catch.
d. Mechanical conditions: Putting out traps that are in poor working conditions is a waste of time and effort.
e. Number of traps: Large number of traps relative to the expected size of the rodent population should be used.
f. Bait used: Fresh aromatic bait that is most attractive to the largest species should be used. Food grains in the houses should be properly covered so that the rat finds only the food in the trap.
Trapping is the preferred method of control in the houses and office building, because animals killed can be easily removed. Traps can be used profitably to deal with poison-shy and scattered survivors of poison campaign.

Control of important species of rats

Lesser bandicoot rat: These attacking tuber crops can be easily controlled by poison baiting in rodent burrows. Firstly, locate the burrows in the field. Open the burrows to a length of 30 to 45 cm. The rats will come and close the burrows with soil within 30 minutes. Then it can be again opened and poison bait can be inserted into the burrow.

From bait preference studies conducted at Entomology Division, College of Horticulture, Vellanikkara, prawn powder is found most effective. Dry prawn available in the market is heated and powdered. A few drops of vegetable oil are added and zinc phosphide 1-2% is mixed with the bait. This zinc phosphide bait can be put inside the burrow preferably on a dry leaf. No pre-baiting is necessary for these rats in the garden lands since it has no bait shyness.

Norway rat: In the Rice Research station, Moncompu these species of rats were causing serious damage to paddy crop. The most effective method of control is using Moncompu trap. Firstly we have to locate fresh rat-damages in the field. These rats cut the paddy plants at the base above the water level in patches. The rats have a habit of coming to the same area on subsequent days. So the traps should be placed in such spots.
 

Release of Cyrtobagous salviniae weevils is found effective for the control of salvinia. Even one pair of weevil is sufficient for establishment in a locality. But for practical consideration 50 to 100 weevils are recommended for release in a particular area. When collection of weevil is not possible, about one kg of infested salvinia can be used as the release material. Release may preferably be made whenever tender salvinia growth is available. If the plants are very old, they may be removed mechanically to promote re-growth and then weevils are to be released. Almost 100% control of the weed will be obtained in a span of 12-18 months.

The rate of natural dispersal of the weevil is rather slow and hence it is desirable that the infested weed mats are redistributed at periodic intervals. In canals used for navigation, the rate of spread of the weevil is found to be quite adequate.
 

VA mycorrhiza
Inoculation with VA mycorrhizal fungi at the time of planting in the nursery or main field improves the growth and tolerance of crop against root pathogens, particularly Phytophthora, Pythium, Rhizoctonia and root nematodes of black pepper, cardamom, ginger, turmeric, cowpea, rice and transplanted vegetables.

Trichoderma
Biocontrol of soil borne plant pathogens involves mass introduction of antagonistic microorganisms in the soil. Trichoderma spp. is a group of broad-spectrum antagonists subjected to detailed studies for their potential as biocontrol agents. They are effective against the quick wilt of pepper (T. viride T6, T. longibrachiatum T2), rhizome rot of cardomom (T. longibrachiatum T2, T. virens T9) and ginger (T. viride T10). A non-axenic system, viz. neemcake-cowdung mixture is used as food base for Trichoderma spp.

Dry neem cake and cowdung are to be powdered and mixed to get a coarse texture and then moistened by sprinkling water. Add the commercial preparation of Trichoderma spp. (available in polythene packets) @ 1-2 kg per 100 kg of neemcake-cowdung mixture. After thoroughly mixing, cover it with a perforated polythene sheet or ordinary newspaper and keep it in shade for 4-5 days for multiplication. Again mix well and keep for three more days for further multiplication. This preparation is ready for incorporation in the soil. Cowdung alone can also be used as the food base; but, since neem cake is found to be a better substrate, the incorporation of neem cake to cowdung at the ratio of 1:10 (w/w) is better than using cowdung alone. If cowdung alone is used, mixing has to be done at 5 days interval and it will be ready for use only on the 15th day. This Trichoderma incorporated neemcake- cowdung mixture can be used in the potting mixture in nursery beds and in the field; i.e. wherever cowdung is used as a manure.

Fluorescent pseudomonas (ad hoc recommendation)

Fluorescent pseudomonas are a group of bacteria very effective against disease incited by species of Phytophthora, Pythium, Rhizoctonia, Fusarium, Colletotrichum, Ralstonia and Xanthomonas in various crop plants in the nursery as well as in the main field.

Two isolates of Pseudomonas fluorescens (P1 and P14) have been developed by the Kerala Agricultural University for the disease management and growth promotion of crop plants. This is found highly effective for the management of foot rot and fungal pollu of black pepper, sheath blight and bacterial leaf blight of paddy, bacterial leaf spot and Phytophthora infestation in betel vine, bacterial wilt of solanaceous vegetables, bacterial leaf blight of anthurium and Colletotrichum and Phytophthora infestation in vanilla and rhizome rot of ginger. The organism significantly improves the growth and biomass production of crop plants.

Method of application

The talc-based formulation at 1-2% level may be used for soil drenching and spraying. Seedlings/cuttings are treated with Pseudomonas culture by dipping the root/tip of cuttings in slurry of Pseudomonas (250 g in 750 ml for 20 minutes). For seed treatment in paddy use 10 g talc-based Pseudomonas culture for 1 kg of seed; suspend Pseudomonas in water used for sprouting. This helps in the control of fungal and bacterial diseases.

For transplanted crop dip the roots at the time of transplanting, and one spray may be given at 30th day after transplanting. For black pepper, drenching the nursery plants immediately after planting followed by one or two sprays depending on the extent of disease. For managing foot rot of pepper in the main field, drench the base of the vine and spray the plant with Pseudomonas fluorescens @ 10 g/litre at the onset of monsoon. A second spray may be given, if necessary during the mid-monsoon period.

For all the crops, the time of application and the frequency of application may vary depending on the incidence and intensity of the infection. A combined application of Trichoderma and Pseudomonas fluorescens may be resorted to at the time of planting in the nursery and/or main field for the control of diseases of pepper, cardamom and ginger. The application may be repeated based on the intensity of disease incidence.

Chemical fertilizers and plant protection chemicals should not be used along with biocontrol agents.
 

Solarization is a method of hydrothermal disinfection. This is done by covering moist soil with transparent polythene sheet and exposing it to direct sunlight during the hottest period of the year.

Method of solarization

a. Nursery bed
The nursery bed for raising seedlings is to be levelled and pebbles present on the surface removed before solarization. Incorporate the required quantity of organic manure in the soil and irrigate @ 5 litres per m². Cover the beds with 100-150 gauge transparent polythene sheets. Seal the edges of the sheet with soil to keep it in position in order to maintain the temperature and moisture inside the polythene mulch. Adequate care is also to be taken to see that the sheet is in close contact with the surface of soil to prevent the formation of air pockets between the soil and polythene sheet. Keep the sheet in this way for 20-30 days. Protect it from stray animals and birds. After the period of solarization, remove the sheet and the bed is ready for sowing and transplanting.

b. Potting mixture
The required type of potting mixture is to be prepared as per the recommended practice. Spread this mixture on a levelled ground to a height of 15-20 cm. Moisten with water using a rose-can and cover the soil with polythene sheet and solarize for 20-30 days as described above. After solarization, the soil can be used for sowing/planting. This method is found to be very effective to raise disease free pepper cuttings.

c. Main field
Solarization can also be effectively used for the control of soft rot of ginger and similar soil-born diseases in the field. The land used for planting ginger is initially prepared to a fine tilth and pebbles removed. Prepare raised beds as per the recommended practice. Apply organic manure before solarization. Irrigate the bed once (5 l/m²) and cover with polythene sheet. Leave the bed without any disturbance for 20-30 days. After this period, remove the sheet and plant rhizome bits. All the other agronomic practices are to be followed as per the package of practices recommendations. Biopesticides and fertilizers can be incorporated in soil after removing the polythene sheet.

Hints for solarization
1. Solarization is to be done in open field without any shade.
2. Transparent thin polythene sheet (100 to 150 guage) is to be used, as it is both cheaper and more effective in heating due to better radiation transmittance than thicker sheets.
3. Summer months are more suitable for solarization.
4. Soil should be kept moist during solarization to increase the thermal sensitivity of resting structures of soil-borne plant pathogens and weeds, and to improve heat conduction.
5. Solarization period may be extended to one month or more to ensure pathogen control at deeper layers.
6. Summer showers will not affect solarization. However, excessive seepage of water into the bed during solarization should be avoided.
7. Potting mixture should never be heaped and solarized, as this will drastically reduce the efficiency of the technique.
8. Soil should be in good tilth allowing close contact between the plastic sheet and the soil to prevent the formation of air pockets, which reduces heat conduction.

Benefits of solarization

1. Control of fungal pathogens: Several soil borne pathogens can be controlled by solarization. This includes fungi like Pythium, Phytophthora, Fusarium, Rhizoctonia etc.

2. Control of nematodes: Population reduction of nematodes like Meloidogyne, Heterodera, Xiphinema, etc. has been achieved by solarization.

3. Control of weeds: A number of commonly occurring weeds particularly annuals can be effectively controlled by solarization. These include, among monocots, Cynodon dactylon, Cyperus rotundus and Digitaria ciliaris and among dicots, Crotalaria muconata, Indigofera hersuita and Noxia sp.

4. Plant growth response: Increased growth response is observed in plants cultivated in solarized soil. This is mainly evident as increase in plant height, number of leaves, better root formation, increased root nodulation in legumes and yield.
 

Species of Pleurotus commonly known as oyster mushrooms grow saprophytically under natural conditions on trees, dead wood, stumps and branches. Today several species of Pleurotus are commercially grown in many parts of the world. Kerala enjoying a typical tropical climate is found to be the most suitable place for mushroom cultivation. Species of Pleurotus and Volvariella can be successfully cultivated in the State all round the year on a variety of agro-wastes like saw dust, vegetable and paper wastes, oil palm pericarp waste and straw. But the best suitable substrate is found to be paddy straw.

Variety
Ananthan is a short duration variety released from KAU. It is an inter-stock hybrid of Pleurotus petaloides; tough fleshed, pure white in colour, pest and disease resistant; and yields about 100-120 g per harvest. It has good cooking quality and consumer acceptability and can be grown in wheat, paddy and sorghum straw. On an average, it takes eight days from spawning to harvest. Yield potential is 800 g per kg straw.

Method of cultivation
Polythene bags or tubes of 30 x 60 cm size with 150-200 gauge are taken for filling the substrate. If the tubes are used, the free-end is tied with a string. Seven to eight holes of 0.5-1.0 cm diameter are made all over the bag for aeration. One kg of well dried, one-year-old paddy straw is cut into small bits of 5-8 cm in length and immersed in water for 18 hours. Then the soaked straw is taken out from water and kept inside the basket for 1-2 hours to drain away excess water. The soaked straw is kept under boiling water (100ºC) for 30-40 minutes for surface sterilization or to achieve pasteurization and then taken out and kept inside the basket to drain excess water and allowed to cool down. The pasteurized straw is ready for filling the bags. Instead of straw bits, small round bundles of 20 cm diameter are also used for filling the bags. This method is followed to save time and labour. Now the perforated polythene bag is filled for about 5 cm height with the above processed straw and pressed with hand for making it even. Care should be taken to fill the bags as compactly as possible for the proper growth of mycelium. For getting maximum yield, 2-2.5% (125 g) of spawn is used. Spawn is taken out from packets and kept inside a clean container or paper. From this, one tablespoon full of spawn is sprinkled over the filled straw around the peripheral region. A second layer of processed straw is filled and spawned as above. Repeat the process as above until the soaked straw is finished. Every time before spawning, press the straw with hand for making it compact. If bundles are used for filling the bags care should be taken to keep the bundles inside the bag as compact as possible without leaving any space in between the bundle. Finally the bag is closed tightly with twine and beds are kept undisturbed for spawn running for about 15-20 days inside the rooms, thatched rodent-proof sheds or in verandas. The best temperature and humidity for spawn running ranges from 28-30ºC and 80-85%, respectively. The beds can be arranged over a platform or in shelves. The spawn running can be judged from the whitish growth covering the straw completely. Periodically observe the beds and discard the contaminated ones. After 15 days when the spawn running is complete, remove the polythene bag by cutting it with blade and keep the bed for sporocarp formation. The opened beds are kept in well-ventilated rooms. Relative humidity of the room should be 80-85%. If temperature inside the room rises above 30ºC, the room should be sprinkled with water to lower the temperature. Diffused light is essential for normal fruiting. Pinhead formation starts on 20th day and 2-3 days are required for the maturation of the fruiting body.

Cropping and yield
Matured and fully opened sporocarps are harvested by placing the thumb and forefinger near the base of the fruiting body and twisted in clockwise direction to get detached from the mycelium. An average yield of 500-700 g can be harvested from 1 kg of straw. The spent straw can be used as enriched cattle feed.

Table 29. Salient characters of common edible species of mushrooms of Kerala

Cultivation of paddy-straw mushroom (Volvariella volvacea)
The paddy straw mushroom can be successfully cultivated in the plains of Kerala throughout the year where the temperature ranges between 28-32ºC. The straw beds can be laid out in sheds, veranda of buildings and during summer under shades of trees. Beds should not be kept under direct sunlight. Prepare a raised platform of 1 m long and 0.5 m broad with wooden planks or bricks. Ten to fifteen kg of well-dried and hand-threshed straw is required to raise a single standard bed. For spawning this bed, two bottles of spawn and about 100 to 150 g of red gram powder are needed. First the straw is made into twists of about 5 to 8 m long and 20-25 cm diameter. The twists are tied into small bundles and are kept immersed in clean water in tanks for about 6 to 12 hours. After this, the bundles are taken out and kept aside for some time to drain the excess water. The bundles are untied and the straightened twists are placed length-wise over the platform in a zigzag fashion. The twists are placed as close as possible. Keep another layer over the first layer crosswise. These two layers form the first layer to be spawned. Break open the spawn bottles and carefully divide the spawn into small bits of 2-2.5 cm thick. Place these bits of spawn all along the periphery of the bed, about 5-8 cm away from the edge and 10 cm apart. Sprinkle a teaspoon full of coarsely powdered red gram powder before and after spawning the first layer. Build the next layer with one row of twist as done before and spawn it. Make successive layers until the straw twists are finished. After placing the last of twists, press the bed thoroughly from the top in order to drain excess water. Make the bed as compact as possible and cover with a transparent polythene sheet to maintain the temperature and relative humidity within the bed. Place another wooden plank over the bed and keep 4-5 bricks above the plank to get more compactness. Keep the bed undisturbed for 6-7 days. Slowly remove the sheet and observe the moisture level of the straw. If the moisture is excess remove the sheets for half an hour and then cover it again as before. Small white round pinheads appear all along the sides of the bed after 7 days and mature into button and egg stage on 9th day. Harvest the mature sporocarps in eggs stage. About 2-3 kg of mushrooms can be harvested from 10 kg of straw. Cropping lasts for 2-3 days. After the harvest, the spent straw can be sun-dried and used as cattle feed.

Instead of twists, the beds can be laid out using small bundles of straw each weighing about one kg. Place four such bundles of straw side by side over the platform with loose ends towards the same direction. Over this, place another four bundles, the loose ends towards the opposite direction. These eight bundles form one layer, which is to be spawned as in the case of twists.
 

Plant tissue culture is the in vitro culture of plant cells, tissues and organs under aseptic condition in defined or semi-defined media. Tissue culture techniques are increasingly being used for the rapid vegetative propagation of plants. It helps in the mass clonal propagation of crop plants. It is useful for plants, which do not set seeds or where the viability of the seeds is poor. Even when conventional methods of vegetative propagation are commercially acceptable, tissue culture propagation can be adopted as it has definite advantages. It offers an extremely rapid rate of multiplication. The geometric progression of tissue culture propagation makes it possible to produce millions of plants from an initial explant in a few months. It can speed up the process of establishing new varieties. Only a limited quantity of plant tissue is required as the initial explant. Tissue culture propagation ensures the availability of plants throughout the year. It helps in the production of uniform progeny from cross-pollinated plants. Disease-free planting materials can be made available to the farmers. Special laboratory facilities and technical skill are essential for adopting this technique for mass multiplication of crop plants. Training in tissue culture is offered by various research organizations in Kerala.

Procedure
Pipette out the required volume of stock solutions of chemicals into a one-litre glass beaker. Add components like sucrose and myo-inositol as solid and allow them to dissolve. Make up the volume to approximately 950 ml with distilled water. Adjust the pH to the required value (5.6 to 5.8 for Murashige and Skoog basal medium) with a few drops of either alkali or acid, using a pH meter. Add the required quantity of agar and make up the volume to 1.0 litre. Pour the solution into a glass beaker and heat, while stirring, until the agar is dissolved. Dispense the medium (5 to 15 ml) in test tubes or flasks and plug with cotton. Plastic lids or aluminum foil may also be used for the purpose. Culture jars may be plugged with plastic lids. Autoclave the vessels containing culture medium for 15 minutes at 1.06 kg/cm² pressure (121ºC). While using a pressure cooker, wait for the continuous flow of pure steam, put the weight and sterilize for 20 minutes. Explants collected from field grown plants will have to be disinfected before inoculating in the culture medium. The explants are washed in running tap-water first and then in soap solution. They are then surface sterilized and trimmed using sterile knives. The commonly used surface disinfectants are sodium hypochlorite (0.1 to 2.0 per cent for 15 to 30 minutes) and mercuric chloride (0.05 to 0.1 per cent for 3 to 20 minutes). The efficiency of the surface sterilant can be increased, by adding a few drops of surfactants. After surface sterilization, the explants should be washed with sterile distilled water four to five times to remove the residues. The explants are then transferred to the sterile culture media in vessels. This process is called inoculation. Surface disinfection and inoculation must be carried out in a laminar airflow chamber. This equipment can filter the air through a high efficiency particulate air (HEPA) filter of very small mesh size. This will remove bacteria and fungal spores. The steady outward flow of filtered air will ensure a sterile zone in the equipment, suitable for aseptic manipulations. The needles, forceps, blades and petri-dishes used for the manipulation of explants should be pre-sterilized.

The tools used in the airflow cabinet may be kept dipped in 70 per cent ethanol in a beaker and periodically flamed over a spirit lamp. After inoculating the explants in suitable culture media, the cultures are incubated in rooms under controlled conditions of temperature (26 ( 2ºC), light (200 lux, 18 hours) and humidity (60-80%). Response of an explant largely depends on the composition of the culture medium. There are several basal media, which can be used for various needs with necessary modifications. The basal medium is selected to suit the plant species and the method of in vitro culture. In general, culture medium consists of salts of major and minor nutrient elements, vitamins, and amino acids, plant growth substances and a source of carbon. The established cultures are sub-cultured to fresh media at intervals of 3 to 5 weeks. The media provided at each subculture decide the response of the tissue. Hardening the plantlets to make them adapt to the outside environment is a critical process, essentially due to the anatomical and physiological peculiarities of the plantlets. A period of humidity acclimatization is necessary for the newly transferred plantlets to adapt to the outside environment, during which the plantlets undergo morphological and physiological adaptations, enabling them to develop typical terrestrial plant-water control mechanism.

Tissue culture techniques for mass multiplication have been standardized for crops like banana, pineapple, papaya, black pepper, cardamom, vanilla, orchids, anthurium, gladiolus and several medicinal plants. The commercial adoption of tissue culture clonal propagation is feasible only when the rate of multiplication is satisfactory and the cost of plantlets is acceptable to the farmers. Protocols for the tissue culture propagation of a number of crops like red banana, Nendran, pineapple, orchid and anthurium, black pepper, vanilla, medicinal plants etc. have been developed at the Kerala Agricultural University and are available for commercial adoption.
 

About 30 to 40% of the harvested fruits and vegetables are estimated to be lost due to improper harvesting, handling, storage and transportation in India. If proper care is taken during these operations, the loss to some extent can be minimized. Some of the techniques, which can be adopted, are as follows.

Harvesting
a) Harvesting must be done at the appropriate maturity depending up on the marketing distances and purpose.
b) Harvesting must be done preferably in the morning hours or late evening to avoid exposure of the produce to excessive heat, which will otherwise hasten spoilage.
c) Harvesting must be done preferably with suitable harvesting devices to suit the commodity and reachability; e.g. mango harvesters with cutting edges and plastic net can prevent the damage during harvest and collection.
d) Avoid impact shock while harvesting fruits from tall tree; e.g. jackfruit, mango, etc. which will cause bruising leading to infection.
e) Avoid loose or too tight packing in gunny bags while transporting harvested produces to avoid bruising.

At packing
a) Wash the harvested produce in plain water or in chlorinated water to clean the adhering mud, dirt and residual pesticides.
b) Remove the infested, rotten and spoiled ones.
c) Grading the produce can improve market acceptability. This can be done at farmers' level or at the co-operative sector to suit the standards established by individuals, industry or government. Grading will also increase farmers' bargaining power, as they are likely to get quality premiums for better-graded product. Similarly buyers can choose the grades they wish to buy. Possible grading can be based on colour, shape, size, weight etc. of the commodity

During storage
a) Pre-cool the commodity immediately after harvest to reduce the field heat.
b) Pre-packaging the commodity into unit packs can reduce the handling losses.

Some of the packaging techniques are (1) Packing of banana hands at 0.2 to 0.4% ventilation with polyethylene cover of 150 gauge was found to increase the keeping quality up to 10 to 12 days under ambient conditions. (2) Packing of fresh mushroom (Pleurotus sp.) with 100 gauge polypropylene pouches without any ventilation can extend the storage life up to 36 hours in room temperature and up to 7 days under refrigerated conditions. (3) Fresh tomato can be stored up to 25 days under ambient conditions when packed with 35 to 40 per cent moistened saw dust in a ratio of 1 : 0.5 (tomato : saw dust). (4) Fresh mature and ripe sapota can be stored up to 6 days under ambient conditions when individually wrapped with cling film.

General storage methods practised to extend the keeping quality are:

1. By storing the commodity under optimum low temperature and humidity.
2. By skin coating using wax emulsion containing permitted fungicides at optimum concentrations.
3. By controlled/modified atmospheric storage modifying the oxygen/carbon-dioxide ratio within the package.
4. By sub-atmospheric pressure storage.
5. By ventilated storage using ventilated films/bags.
6. Using evaporative cool chamber constructed to store temporarily the harvested produce at the field before marketing.
 

Indigenous auto irrigator can be fabricated by fitting certain low cost accessories in ordinary garden pot. Plug the holes of the garden pot with corks provided with holes. Insert hospital drips through these holes.
Garden pots designed in the manner can serve as auto irrigator. One auto irrigator can serve as water source for maximum six pots. Place the irrigator at a level above plant height and arrange the potted plant around this auto irrigator. Plants are irrigated by exploiting gravitational force. Adjusting the regulator attached to the hospital drips can regulate the flow of water. Irrigate the pots to bring it to field capacity. Daily loss of water from the pots can be computed. The flow rate can be adjusted according to water requirement of the plant.
 

Manually operated paddy transplanter
The improved IRRI six-row paddy transplanter is simple in construction and easy to operate. Six numbers of seedling mats having size 20 x 50 cm are placed in the transplanter tray, which is operated by a single person. It weighs only 20 kg.
It is operated in puddled and leveled fields with a thin layer of water. Row spacing is 20 cm and hill spacing is adjustable. It covers approximately 0.1 ha/h and has a saving of 75% labour and 70% cost in transplanting. Approximately, this costs Rs 3000.

Yanji Shakti 8-row rice transplanter
Rated speed: 2600 rpm; row number: 8; row spacing: 238 mm; distance between hills: 120-140 mm; number of seedling per hill: 3-8; suitable width of seedling mat: 2-20 mm; planting depth: 0.60 mm.

5 HP self-propelled paddy reaper
The 5 HP engine-operated improved IRRI reaper harvests paddy in 1 m width both in dry and wet fields of Kerala, except in sticky kole fields. A person operates it by walking behind the reaper. Maximum recovery of grain and straw is achieved.

It harvests broadcasted or transplanted non-lodged paddy. It is suitable for own use as well as for custom hiring. It covers approximately 0.18 ha/h and has saving of 85% labour and 65% cost in harvesting paddy. Approximately, this costs Rs 40,000 including diesel engine.

Tractor operated paddy reaper
The tractor front mounted paddy reaper harvests at 2.2 m width. Power is taken from PTO for cutting and conveying the crop and the hydraulic system is used for controlling the height of cutterbar. It is suitable to any make of tractor. Cage wheels and pneumatic wheels are used for wet and dry fields. Broadcasted or transplanted non-lodged paddy can be harvested. Maximum recovery of straw and grain is achieved. It is suitable for tractor owners for custom hiring. It covers approximately 0.4 ha/h and has a saving of 85 % labour and 65% cost in harvesting. Approximate cost is Rs. 25,000.

Portable power-operated rasp-bar paddy thresher-cum-winnower
The crop is fed in the thresher with modified concave powered by an 8 HP engine. After threshing and winnowing it delivers straw, chaff, stone and clean paddy in separate outlets. It has good threshing and winnowing efficiency. Transportation is made easier by its pneumatic wheels by a pair of bullocks, power tiller, jeep or tractor. It is suitable for paddy crops even with high moisture and long straw. Suitable for custom hiring. Straw is not cut and damaged. It threshes crop from approximately 0.3 ha/h (100 kg/h) and has saving of 85% labour and 60% cost in threshing paddy. Approximate cost is Rs 30,000 without engine.

KAU jack-fruit harvester
This consists of two sub-units as adjustable telescopic long handle with a hood knife at the outer end and a basket suspended from a nylon rope. The basket can be located just around the fruit by a handle and rope and then harvested into it for safe lowering. It can be used for normal and medium tall trees. With two people, a fruit can be harvested in 4-5 minutes. Weight is 4-5 kg (if made of aluminium). Approximate cost is Rs 500.

Petti and para
The petti and para is used very widely to dewater the low-lying kole lands and Kuttanad padasekharams. These are not operated at optimum speeds, and hence incur loss of energy. The optimum speed for high level of efficiency at relatively higher head (100-200 cm) has been found to be 330-340 rpm for a 15 HP pump. Beyond 340 rpm, the pump gets overloaded.

Coconut husking tool
This consists of a stationary wedge, a movable wedge, a lever and a pedestal having a base. The stationary wedge is mounted upright on top of the pedestal at a convenient height. Bottom of the movable wedge is hinged to the bottom of the stationary wedge facilitating its opening and closing. The lever fixed to the movable wedge provides the necessary mechanical advantage needed in husking. Self-weight of the lever forces the wedges to remain together forming a large wedge. Holding the coconut with both hands, it is thrust onto the wedge piercing the husk at its pedicle end and parallel to its longitudinal axis. On pulling the lever upwards, a sector of the husk is loosened off. The operation is repeated for the other two or three sectors and the nut is then separated from the husk by pulling with the hands, which is easier. The trade name is Keramithra and approximate cost is Rs 180.
 

Citation:
Kerala Agricultural University. 2002. Package of Practices Recommendations: Crops. 12th Edition
(eds. A. I. Jose et al.). Kerala Agricultural University, Trichur. 278p.