Plant Protection

Adopt control measures only if the pest / disease population exceeds the economic threshold levels.

Economic threshold levels (ETLs)

Source: Manual on Integrated Pest Management in Rice, Directorate of Plant Protection, Quarantine and Storage.

Note:

(1) The population should be estimated on the basis of careful and regular surveillance.

(2) When natural enemies of brown plant hopper, green leaf hopper, stem borers and leaf folders are present, application of chemical measures can be delayed or dispensed with.

Pests

Rice stem borer (Scirpophaga incertulas)

Symptoms

In the vegetative phase, the central shoot dies off turning yellow in colour (dead heart). In the ear bearing stage, the ear head appears completely chaffy and white in colour (white ear head). Both come out easily when pulled up and show indication of feeding injuries at the base.

Scirpophaga incertulas	New emergence
Whitehead or dead panicles	Drying of central tiller

Management

1. Collect egg masses from the nursery plants and observe for parasitisation.
2. Cultivate tolerant varieties like IR-20 in endemic areas.
3. In areas where stem borer occurs as a serious pest in all seasons, apply any one of the following insecticides first 15-20 days after transplantation and then at the boot leaf stage keeping minimum water level: quinalphos (spray or granules), carbosulfan, cartap hydrochloride (spray or granules), Flubendiamide, indoxacarb, malathion or spinosad, Fipronil, Chlorantraniliprole..
4. Use sex pheromone for the control of rice stem borer as given in the table below:

Sex pheromone used for the control of rice yellow stem borer (ad hoc recommendation)

Gall midge (Orseolia oryzae)

Symptoms

Presence of silver shoot in the place of central leaf is the prominent symptom. The symptom appears from the nursery to the flowering stage. However, in very young seedling the silver shoots are not always expressed. Instead, a swelling at the basal portion and excess tillering are often noticed.

Gall midge	Feeding site of immature gall midge	Infected tillers

Management

1. Use tolerant varieties like Pavithra, Panchami and Uma.

2. Avoid late transplantation during the first crop season.

3. Careful monitoring of the crop seasons in the month of July during additional crop season and October during puncha season.

4. Use optimum seed rate of 100 kg/ha.

5. Destruction of collateral host like wild rice, Cynodon dactylon, Ischaemum aristatum, Echinochloa spp. and Isachne sp.

6. Dipping germinated seed in 0.2% chlorpyrifos solution for 3 hours before sowing give protection up to 30 days.

7. In transplanted crop the root of seedlings may be dipped in 0.02% chlorpyrifos suspension for 12 hours prior to planting.

8. The nursery treatment has to be followed by main field treatment, 10-15 days after transplantation using anyone of the following insecticides: quinalphos. Carbosulphan 6G, Chlorantriniliprole 4 G, and Fipronil.

9. In areas where the pest is of regular occurrence, apply granules of quinalphos (250 g ai/ha) or chlorpyrifos 10G (0.5 kg ai/ha) within 10 days after sowing. The granules should be broadcast in 2-3 cm of water and the field should be impounded for at least 4 days.

Rice bug (Leptocorisa acuta)

Symptoms

Look for the presence of bug in the field during the early ear bearing stage. Due to de-sapping, grains show brownish discoloured patches on the husk.

Rice bug adult	Affected rice grains

Management

1. Strict vigilance is necessary at milky stage.

2. Keep the field and bunds free of weeds and grasses.

3. Avoid overlapping cultivation in an Ela.

4. When the bug is seen in large numbers apply one of the following insecticides: Malathion and carbaryl.

Note: Since the occurrence of the bug coincides with the flowering stage, application of the insecticide may be done either before 9 a.m. or after 3 p.m. so that fertilization of the flowers is not adversely affected.

Leaf folder (Cnaphalocrocis medinalis)

Symptoms

The leaves of the plant are seen folded, rolled and often webbed together with white patches on them indicating the areas fed by caterpillar. When such folded leaves are opened up, larvae can be seen. Shaded conditions and application of excess nitrogen are conducive for leaf folder attack.

Cnaphalocrocis medinalis	C. medinalis larva	Leaf folds

Management

1. Open up the leaf folds with the help of a thorny twig.

2. Apply one of the following insecticides in the field where the symptoms of attack are manifested: quinalphos, phosalone, cartap hydrochloride, flubendiamide, acephate, indoxacarb and dichlorvos, Carbosulphan 6G, Chlorantriniliprole 4 G.

Note: - In the initial stages restrict spraying to infested patches only. The field may be sprayed completely in case the infestation occurs uniformly.

Eco-friendly management:

1. Trichogramma japonicum and T. chilonis each @ 1 lakh/ ha + Beauvaria bassiana @ 10gm/ litre

2. Chitin based pseudomonas @ 2.5 kg/ha, Bacillus thuringiensis @ 200 g/ha, fish jiggery extract @ 6ml/litre, azadiractin 1% @ 750 ml/litre.

Brown plant hopper (Nilaparvata lugens)

Symptoms

Yellowish circular patches appear here and there in field. The plants in these areas dry up very soon (hopper burn) and the yellowing and drying extend rapidly. Examine the plants as soon as the yellowing appears. Presence of the hoppers at the base of the plants confirms the infestation. Very close planting leads to enhanced attack.

Nilaparvata lugens	Damaged field

Management

1. Use resistant varieties such as Jyothi, Bharathi, Aiswarya, Kanakom, Nila etc. for cultivation.

2. Apply one of the following insecticides as soon as the yellowing symptom is observed, covering the infested patches and the areas surrounding the patches: Buprofezin, ethofenprox, quinalphos, thiamethoxam, acephate, phosalone and imidacloprid. While spraying and dusting, care has to be taken to see that the insecticides reach the base of the plants.

3. Drain away water from the field and keep it in that conditions until the pest population dwindle.

4. In Kuttanad tract, early planting of paddy in September-October is advisable, wherever possible.

Rice case worm (Nymphula depunctalis)

Symptoms

Leaves of plants are eaten by the caterpillars, which remain within small cylindrical cases and are seen hanging on the leaves. It occurs in ill drained fields. The cases may be seen floating on water also.

Nymphula depunctalis adult
Floating cases	Damaged leaves

Management

1. Drain away the water from the fields.

2. eco- friendly management: Chitin based pseudomonas @ 2.5 kg/ha, Azadiractin 1% @ 750 ml/litre

Rice swarming caterpillar (Spodoptera mauritia)

Symptoms

It appears in the field sporadically and cyclically in large swarms and feed on crops gregariously. The nursery and early stages of the crop are attacked leaving the plant as mere stumps.

Spodoptera mauritia	Damaged leaf blades	Panicle damage

Management

Flood the fields or apply trichlorphon   as soon as the caterpillars are noticed.

Rice hispa (Dicladispa armigera)

Symptoms

The adults feed on the green tissues of the leaves and the feeding scars appear as short white lines on the leaf surface. The grubs mine the leaves causing formation of white blotches. Early stages of the crop are more susceptible.

Dicladispa armigera	Field damage

Management

Spray any contact insecticide.

Rice thrips (Stenchaetothrips biformis)

Symptoms

The crop is highly susceptible in the nursery stage for the first 23-25 days after transplanting/sowing. The tips of leaves get rolled longitudinally into needle like outgrowths and turn whitish. In severe cases, the lower leaves also turn yellowish. The infestation may be rated as mild, if there is less than three needle like leaves and as severe, if there are more than three outgrowths with the lower leaves also showing chlorosis and scorching.

S. biformis adult	S. biformis larva	Leaf curls

Management

In severe infestations, apply DDVP 100% EC/AF 250 ml/ha or dimethoate or quinalphos or phenthoate (EC/AF formulation).

Whorl maggots (Hydrellia philippina)

Infestation is common in the nurseries and in the main fields up to six weeks after transplantation. Yellowish patches and streaks are seen along the margins of leaves, which may become deformed.

Hydrellia philippina	Leaf damage

Management

Apply malathion if infestation is severe.

Leaf hoppers (Nephotettix spp.)

Symptoms

General yellowing of the leaves is seen, if the attack is severe. When the plants are disturbed, the jassids are seen jumping out.

Nephotettix spp.	Damage in the field

Management

Apply quinalphos, flubendiamide or imidachloprid if needed.

Rice mealy bug (Brevennia rehi)

Symptoms

Weak yellowish stunted plants are seen in patches. White waxy fluff is seen in leaf sheaths.

Management

Dimethoate at 0.05% is effective in controlling the pest.

Rice root nematode (Hirschmanniella oryzae)

Symptoms

Infests paddy roots and make them partially hollow. Feeding adversely affects absorption of water and nutrients. Plants show stunted growth in patches. Tiller production is affected.

Management

Dip the roots of seedlings in 0.2% dimethoate for six hours before transplanting in tracts were nematode attack is detected.

Rice cyst nematode (Heterodera oryzicola)

The cyst nematode occurs in various proportions in certain areas of state. The symptom of infestation include leaf chlorosis, stunting, and reduction in number of leaves, earhead lenth etc..in seriously affected patches, the yield is reduced.

Insecticide guide for rice pest control

SP = Soluble Powder; DP = Dustable Powder; G = Granule; EC = Emulsifiable Concentrate; AF = Aqua Flowable;
WP = Wettable Powder; S = Sprayable suspension, SL = Soluble liquid, SC = Suspension Concentrate, WDG = Water Dispersible Granule. 

Note:

1. Sub-lethal concentration of insecticides may lead to pest resurgence.

2. Granular application is recommended only up to the booting stage.

3. Spot application method should be resorted to wherever possible

4. Use 200, 300 and 500 l/ha of spray fluid at 10, 25, 45 DAT or 30, 45, 60 DAS respectively for high volume spray equipment.

5. When low volume spray equipment is used the spray fluid can be limited to 90, 120, 180 l/ha, but the quantity of insecticide should remain the same as used in high volume spray 200, 300 and 500 l/ha respectively.

6. Waiting periods for quinalphos and malathion are 7 and 3 days respectively.

7. In regions where BPH is a regular pest avoid the application of the following insecticides due to the chances of resurgence: Deltamethrin, carbaryl and quinalphos.

Diseases

Fungal diseases

Blast (Pyricularia grisea)

Major symptoms of the disease are leaf blast and neck blast. Sometimes nodal infection is also seen.

Symptoms on leaves appear as spindle shaped water soaked greyish green spots, which gradually enlarge in size and develop to spots with grey centre and brown margin. Such spots coalesce together resulting in drying up of the leaves and collapse of the entire plant. The fungus infect the neck of the panicle causing dark brown to black lesions resulting in rotten neck or neck blast. This will also lead to breaking of the panicle at the neck region. The grains will be partially filled or unfilled If the panicle is infected before grain filling stage, the entre panicle will be chaffy.

Sheath blight (Rhizoctonia solani)

Symptoms first appear on the lower leaf sheath near the water level as oval, oblong or irregular greenish grey spots, which enlarge and become greyish white with brown margin. Under favouarble conditions, the disease spread to the leaves also. Irregular greenish grey lesions with dark brown margins develop on leaves. Under humid conditions, white mycelial growth of the fungus as well as initially white and later brown sclerotia of the fungus loosely attached to the affected portion are also seen.

Brown spot (Helminthosporium oryzae)

On the leaves small definite spots of oval or oblong shape and dark brown colour are formed. On susceptible varieties, spots are larger in size and are having light brown or grey center with dark reddish brown margin. The symptoms also appear on glumes as black oval or oblong spots or whole surface of the grain turn black and velvety.

Narrow brown spot (Cercospora oryzae)

Numerous narrow linear short brown spots are formed on the leaves.

Stack burn (Alternaria padwickii)

Symptoms appear on leaves as large oval or circular dark brown lesions with narrow distinct margins. On the affected grains pale brown to whitish spots with dark brown margin bearing black dosts in the center are formed.

Leaf scald (Rhynchosporium oryzae)

Lesions with typical zonations with dark coloured wavy lines usually start from the tip of the leaves and extend downwards or arise from the margin and advance inside.

Sheath rot (Sarocladium oryzae)

The fungus infects the leaf sheath enclosing the panicle causing oblong or irregular brown spots which later develop into a lesion with dark brown margin and grey center. The young panicle remains inside the sheath or rather chocked and emerge only partially. The grains become chaffy A white powdery growth of the fungus can be seen on the surface of rotten sheath particularly inside the sheath.

False smut (Ustilaginoidea vireus)

The symptoms visible only after flowering when infected grains get transformed to yellow to orange spore balls, which later turns to dark green or black.

Udbatta (Ephelis oryzae)

Whole panicle transformed into a cylindrical rod covered with white mycelia Later they become hard bearing many black dots.

Foot rot (Fusarium moniliformae)

Drying of leaves and leaf sheath discolouration of lower nodes and adventitous root formation are the major symptoms. Plants turn pale yellowish green, thin and some times show abnormal elongation or rot in patches in the field.

Bacterial diseases

Bacterial blight (Xanthomonas oryzae pv.oryzae)

Bacterial blight is chararcterised by two phases of infection Kresek and leaf blight Kresek is drying or wilting of the whole plant if affects the crop in early stages of growth in nurseries and upto 3-4 weeks after transplanting. The infected leaves become grayish green and begin to roll along the midrib and dry in severe cases the affected hills may be completely killed.

Leaf blight symptom start as water soaked lesions on the tip of the leaves and increases in length downwards along the margins. lnitially the lesions are pale green in colour and later turn into yellow to straw coloured stripes with wavy margins. Occasionally the linear lesions may develop any where on the leaf lamina or along the midrib with or without marginal stripes Lesions may cover the entire leaf blade. The bacterial blight disease can be confirmed by ooze test. Cut the affected plants at the base and dip it in a glass of water and hold it against the light for few minutes without shaking. From the cut ends white milky bacterial ooze will come out as streams.

Bacterial leaf streak (Xanthomonas oryzae pv oryzicola)

Narrow brownish yellow translucent interveinal lines joining to form large dirty white patches.

Note :

1. Spray fresh cowdung extract for the control of bacterial blight. Dissolve 20 g cowdung in one litre of water; allow to settle and sieve. Use supernatant liquid.

2. Application of bleaching powder @ 5 kg/ha in the irrigation water is recommended for checking the spread of bacterial leaf blight particularly in the kresek stage.

3. Before application of antibiotics for the control of bacterial blight, identify the disease by observing the bacterial ooze.

4. For control of sheath blight and sheath rot the following prophylactic measures may be adopted.

a) Apply neem cake-coated urea as recommended under fertilizer application.

b) Apply 50 per cent more potash than normal recommended dosage in split application.

c) Control weeds as suggested under weed control.

5. For control of sheath rot, spray the fungicides at the time of panicle emergence.

6. In organic farming, for the management of sheath blight of rice, spraying Azadirachtin 0.03 per cent EC or Azadirachtin 0.15 per cent w/w @ 2.5 litres/ha at the time of first disease appearance.

7. Spraying of any fungicide, preferably dithiocarbamate before the heading stage of the crop may be followed for the control of false smut and leaf scald diseases. Wherever control measures are adopted for sheath blight and sheath rot diseases, separate treatments are not needed for the control of leaf scald and false smut. Use 500 litres of water for high volume spraying and 200 litres for low volume spraying. It is advisable to use chemical on a rotational basis than using the same product continuously.

Guide on control of rice diseases

Hints for reducing cost of cultivation

1. Grow a green manure crop like daincha in April-May in areas where the virippu crop is usually transplanted.

2. If azolla is available, this may be applied instead of green leaf or FYM at 5t/ha.

3. Puddle and level the field thoroughly. This will help to reduce the cost of weed control and also the loss of water and nutrients through percolation.

4. Maintain optimum plant density per unit area, i.e., 50 hills/m₂ for medium duration varieties and 67 hills/m₂ for early duration varieties.

5. Plant the seedlings shallow (3-4.5 cm), as shallow planting increases the tillering of seedlings.

6. Control the weeds during the vegetative phase itself. One weeding thoroughly on the 30^th day after sowing is ideal. Use herbicides for weed control, wherever it is cheaper than hand weeding.

7. Under good management practices (vide item 1-6) reduce the dose of fertilizer N to half the present recommended level. Apply the fertilizer when the plant is able to make the best use of it, at tillering and seven days before panicle initiation.

8. When the field preparation and planting are done on rainy seasons, postpone the application of the basal dose of nitrogen to the early tillering stage (10 days after planting).

9. Use of Leaf Colour Chart (LCC): The leaf colour chart (LCC) is an instant, easy and low cost technique for N diagnosis of current crop and N topdressing in rice. The uppermost fully opened leaf of the primary tiller has to be taken for observation. Ten hills are selected at random for an area of 400 sqm and thus 10 leaves form the sample size. The leaf colour is compared with LCC and the readings are taken. The average of 10 readings gives the LCC value of the plot. Observation is taken at 10 days interval from 20 days after transplanting or 25 days after sowing upto heading. If the threshold value is less than 4, N@ 25-30 kg/ha is recommended for application. If the inherent soil N is low, basal N @ 25-30 kg/ha is to be applied.

10.When the amount of available N is limited, apply it 7 days before panicle initiation. This is the best time for top dressing N.

11. Adopt agronomic practices for increasing fertilizer use efficiency such as:

(a) Incorporating ammoniacal N in the reduced zone in the soil

(b) Incubating urea with moist soil (1:6) for 24 hours

(c) Blending urea with neem cake.

12.Choose fertilizer materials, which are cheaper, e.g. urea is cheaper than ammonium sulphate; rock phosphate is cheaper than superphosphate.

13.Apply phosphatic and potash fertilizers once in two seasons in areas where there is no marked response for these nutrients.

14.Adopt integrated pest management against insect pests and diseases.

15. Harvest the crop at optimum moisture content in order to avoid loss due to shedding and also for improving the recovery of rice.

Mechanical Transplanting in Rice

A. Mat Nursery Preparation

1. Use very thin polythene sheet

2. Select nursery area near to the main field

3. Cow dung powder may be incorporated @ one third volume of the puddled soil and spread over the sheet at a thickness of 10-15mm

4. The sheet may be spread after leveling the nursery area

5. Form small bunds along the boundaries of the polythene sheet, after spreading it, to impound water.

6. Mat nursery may be of 900mm width and convenient length

7. Just sprouted seeds (4^th day of soaking) may be uniformly spread over the mat area @ 0.4 to 0.6kg/m²

8. Seedbed may be mulched, preferably using green leaves

9. Sprinkle water over the seedbed for four days twice daily and keep soil in saturated condition. Never allow mat to dry up.

10. On 4^th day remove the mulch and keep standing water to a height of 3/4^th of seedling height. Keep this condition till the end of nursery period.

11. Closely observe the nursery for pest and disease attack and adopt control measures, if required.

12. When seedlings reach a height of 150mm, mat is ready for transplanting.

13. Drain the required mat area 6-12 hours before cutting for feeding into the transplanter trays.

14. Cut the mat strips 225mm wide and 450mm long to match the measurements of the transplanter trays.

15. Do not allow nursery to over grow. Over growing will lead to entanglement of seedlings with fingers of transplanter and clogging of fingers due to thick and hard mat of roots.

B. Main field

1. Prepare the main field adequately, without clods and stubbles interfering with functioning of finger.

2. Prepare main field sufficiently early to avoid floating of puddle while transplanter is working

3. Final preparation may be done on the day of transplanting in case of sandy loam soil, but may be done 3-4 days prior to planting in case of clayey soils, depending upon settling time of the puddle to consolidate.

4. A thin film of water only is needed in the main field at the time of transplanting. (Too much water in the field will lead to floating of seedlings and too dry condition to non-anchoring of seedlings).

5. Main field should have irrigation and drainage facility

6. Wetting of mat may be required while transplanter is in operation.

Multi species integration in rice

Multi species integration is recommended in Kuttanad wetlands to the tune 10000 fishes, 750 broiler ducks and 3-4 male buffaloes/ annum/ ha. Rice season is June-October. Fish fingerlings are stocked simultaneously in nursery ponds dug nearby. Fish species composition of grass carp, rohu and mrigal at 2:1:1 @ 10000 per ha. Broiler duckling variety Vigoya @ 125-150 /ha are grown in duck houses erected over the fish pond simultaneously. Ducklings are fed with formulated feed. Filled over feed and excrements of duck fertilize the fish ponds. The ducklings are grown for 45-50 days and attain 2.5-3 kg. On an annuity basis 5-8 batches of broiler ducks can be reared. Duck excrements to the tune of 9-10 tons are recycled in this way. Paddy fields will be over in 120-125 days. Paddy fields are inundated after rice harvest and fishes are released to the expanded water body. The left over paddy straw on decomposition generate abundant food material in addition to the duck manure flowing down from the nursery pond. The fish species composition of grass carp and cyprinus is capable of feeding aquatic weeds and detritus straw. The field bottoms are tilled during foraging. The fishes are harvested prior to the next paddy season. Rice fields require no land preparation and preliminary weeding if the plant stand establishment is taken up within one week after the fish harvest. The paddy straw and wild grass available is sufficient to grow 3-5 male buffaloes for meat purpose. This farming system is capable to produce 6-8 tons of paddy grain, 1.8 to 2.25 tons of broiler duck, 2.5 to 3 tons of fish and 450 to 500 kg beef meat/ha/annum. Other major rice cropping systems of Kerala are included as